The Daily Nerd

Show long running process output using servlets

2015-10-24T15:44:00.000-03:00

Let's say that a process is launched using a servlet and its output must be displayed, what means sending it back to the browser. Using plain Java without going into details the code to do it is something like :

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException
    {
        resp.setContentType("text/plain;charset=UTF-8");
        PrintWriter out = resp.getWriter();

        final ProcessBuilder process = new ProcessBuilder(new String[] {"/bin/ping", "-c", "20", "localhost"});
        try
        {
            final Process p = process.start();
            int c;
            while( (c = p.getInputStream().read() ) != -1 ) {
                out.print((char) c);
            }
        } catch (IOException e)
        {
            e.printStackTrace();
        } finally
        {
            out.close();
        }
    }

There is more than one problem with this code :

the output is shown only at process completion
if the stop button is pressed at the browser the process will continue executing and no new output will be shown, worsened if the process will run for hours time
printing the stack trace when an exception is thrown is not very useful

Flushing the output after each print statement solves the first issue. The last one depends on the command and else then will not be covered in this post.

Long running process issue

To begin with the process that launched the servlet thread and the process running the launched command are not the same, but because the servlet thread contains the process reference (Process p) when the stop button is pressed at the browser the servlet thread ends and the reference is lost while the process execution continues. There's no way to read the process output (actually it can be recovered at the OS level, but this is not a topic for this post).

A simple solution is to save the process reference in a field for later use in case the current thread is stopped and a new one wants to show the process output. This solution will stop fun at all, then let's look at problems/enhancements this solution poses and go beyond this simple solution !

Using one field to save the current process allows only one process output per JVM to be accessed (the last one saved). Each client identity can be obtained from the session id (just a sample taken for this post) then let's use a map and save the process reference in it. The proposal is to use the http session information as a key because if the consumer is closed (because of TCP/IP time-out, browser stop button pressed or else) the client browser can connect again which uses the same id than before, and detecting this allows running a new command or continue showing the previously interrupted output.

private Map<String,Process> cmdStore = new HashMap<>();

Process p;

synchronized(cmdStore) {

if ( ! cmdStore.containsKey(session.getId()) )
{

p = new ProcessBuilder(new String[] {

"/bin/ping", "-c", "20", "localhost"

                }).start();
            cmdStore.put(session.getId(), p);
        } else
      {
            p = cmdStore.get(session.getId());
        }

}

    try
    {
         int c;
         while( (c = p.getInputStream().read() ) != -1 ) {
                out.print((char) c);
         }
    } catch (IOException e)
    {
        e.printStackTrace();
    } finally
{
        out.close();

        synchronized (cmdStore) {
            cmdStore.remove(session.getId());
        }

}

}

When the process is running, the servlet thread is suddenly stopped, and a new request arrives the not consumed output will be shown only (consumed one has gone already). The implemented solution is to decouple the process output consumption from the servlet thread (introduced in the while loop) thus creating a new thread that consumes the output, and stores it for later consumption, will do the trick.

The previous solution introduces a new problem : communication. How to communicate the produced output to the servlet thread that consumes it ? The basic idea is to let the consumers subscribe to the generated output and let's the producer notify each consumer when a new output is generated.

Implementation

Showing here all the code is a painless and real estate consuming task then I'll explain the relevant classes and code snippets only.

Class CmdExecutor implements the servlet that shows the output to the user and contains stuff to save the process reference for later use. To be honest the reference saved belongs to class Cmd which starts the process and also a new thread (see class Cmd.OutputExtractor) whose main task is to consume the process output, save it and notify the subscribers.

Finally the class CmdOutputDisplay is used by CmdExecutor to display the process output.

Further research

The design involves one thread for each servlet, one for each output (CmdOutputDisplay) and one for each process output consumer (Cmd.OutputExtractor). In a high traffic site this can be a lot of resources and some extra syncing then will be nice to look for a solution that depends less on threads and syncing.

Other topic that caught my attention was using some kind of blocking list to store the process output. The topic here is to use a data structure designed to work under heavy concurrent load. Will be fun to create a new one (stay tuned!)

Consumer notification on a line by line basis (instead of character based) will also help if the process output is quite verbose.

Final thoughts

The cmdStore field access is synchronized and is a common practice to avoid sync by using thread local variables (variables local to each thread). This solution cannot be applied here because is not guaranteed that the same thread is used for subsequent calls from the same browser.

In the same line of thought if we get stuck with synchronized blocks the first think that comes to my mind if this is really a problem. I mean in a high traffic site the contention in each of this blocks might be huge but I'm not sure how bad it is. Would be nice to do some performance testing and some profiling but I guess that the limit will be imposed by the number of processes running or memory consumed or else before this contention is a problem (just a guess, and also depends on the process characteristics such as run time, memory consumption, etc)

Hope you enjoyed this post!

Con esta seguridad yo me subo a cualquier auto

2015-05-15T19:28:00.003-03:00

Normalmente en las ofertas que suelo ver en el mercado de automóviles me encuentro con la impresión que en la compra con cada salto de categoría dentro del mismo modelo el salto de dinero esta mayormente dedicado a brindar facilidades mas relacionadas con una utilidad emocional cuanto más va subiendo el precio.

Por ejemplo hace unos años el salto de un auto "base" (aire acondicionado, cierre de puertas central, levantavidrios eléctricos, 2 airbags frontales y equipo de audio no integrado) a la siguiente categoría (ABS + algunos detalles de estilo) significaba un agregado de dinero D. Para saltar una categoría más la cantidad de dinero era otra vez D pero lo que se agregaba era climatización individual para el conductor y acompañante (básicamente cada uno puede regular la temperatura en forma independiente) más equipo de audio con GPS integrados a la consola del automóvil. Digamos que el segundo salto es mucho menos apetitoso que el primero. En el primero obtengo el agregado de una característica de seguridad interesante (ABS) en tanto que en el segundo es todo "cartón pintado". Yendo un poco más a lo genérico lo que veo es que hay poca oferta en cuanto a seguridad donde los que descollan son solo los automóviles menos accesibles.

Otro ejemplo que se me ocurre son las famosas cámaras de estacionamiento que agregan algunos modelos de automóviles, o la posibilidad de medir la distancia con el obstáculo que está detrás al estacionar marcha atrás. Realmente son útiles ? nos ayudan en algo que no podamos hacer mirando por los espejos retrovisores ? Necesitamos una precisión medida en centímetros para estacionar marcha atrás ? Mi experiencia me dice que no, y de hecho el otro día tuve una situación que me lo confirmó en la cual una persona estaciona muy pegado mi auto, se baja a mirar que tan cerca está, se vuelve a subir al auto y lo corre hacia adelante. Acto seguido viene el comentario "disculpe pero no me acostumbro a estacionar con la camarita".

Sin quererlo en estos días me encontré con estas 2 características de seguridad que me parecieron más que interesantes y, aunque todavía no están disponibles, son un excelente ejemplo de una altamente deseable prestación.

El primero es la posibilidad de generar una visión del automóvil que sea la más cómoda para cada situación y que ayude a minimizar el riesgo de choques. Por ejemplo es mucho más fácil estacionar un automóvil si uno pudiera verlo como si estuviera suspendido a unos 3 o 4 metros. O tal vez poder mirar por arriba de los autos que están estacionados cuando uno sale de un estacionamiento paralelo, o quizás hacer que los malditos parantes delanteros se hagan transparentes cuando se hace un giro. Bueno, todo eso estaría resuelto según este video. Disfrútenlo.

En este otro ejemplo hay algo que me pareció excelso y es el poder comunicarse con el entorno de una forma menos ambigua. Actualmente nos comunicamos a través de señas de luces, bastante limitadas y ambivalentes en algunos casos. Pro ejemplo si un peatón está por cruzar la calle pero no voy a poder frenar a tiempo cómo se lo digo ? qué seña de luces le hago ? las va a interpretar correctamente ?

Otro ejemplo es la mala regulación de las luces, lo que se ve complicado a partir de los nuevos modelos con luces LED que hacen que nuestra nuca tome un brillo fulgurante, y que tengamos que poner filtro solar en nuestra pupilas para evitar que se calcinen.

En este video van a ver no sólo como esa comunicación se ve enaltecida con unas luces láser muy especiales sino que también hay indicación automática de los límites laterales del camino, luces hiper brillantes para manejar en la noche pero que proyectan un halo de sombre sobre los autos que vienen en sentido contrario para evitar el encandilamiento. Gócenlo!

En resumen estas son las funcionalidades quse no sólo me parecen primoridales por su aplicación ala seguridad sino que además hacen un despliegue del uso de ingenio y de la técnica que casi hace alarde de lo poco que la estamos explotando y, quizás, de lo mucho que nos estamos perdiendo.

BajaLibros.com una mínima revisión

2015-04-25T10:30:00.003-03:00

Hoy me encontré con BajaLibros.com, me registré y esto fue lo que encontré después de unos 30 minutos de interactuar con la aplicación Android.

Lo positivo es que en precios da un saldo positivo pero en cuanto a la oferta y la aplicación hay que trabajarla bastante más en lo relacionado a la usabilidad.

La aplicación es lenta (aproximadamente 2 segundos de tiempo de respuesta promedio) y al hacer login muestra tips en la parte inferior del dispositivo que hace que se pierda el foco al poner la password.

Adicionalmente no ofrecen la opción de libros gratis (hay que buscar por la palabra "Gratis") y al marcar un libro para comprar ("Lo quiero") no indica dónde hay que ir a buscarlo libro para poder leerlo, simplemente desaparece esa opción y hay que rastrear a dónde fue a parar. Si se presiona "Descargar" en lugar de bajar el disco al dispositivo lo pone en el carrito de compras. No hay forma de poner los libros comprados en la "Library"

En cuanto a precios una mínima revisión da positivo comparado con Amazon. Si bien los libros en formato electrónico son más caros por un margen amplio la posibilidad de obtener libros en formato digital que Amazon sólo posee en formato papel le da una ventaja importante.

Elvis Presley en la onda Beach Boys de la era digital

2015-02-10T09:43:00.001-03:00

Esta mañana escuchaba en la radio el tema Return to Sender y no pude evitar el notar cierto parecido temático, y lo digo a riesgo de cometer una herejía, con las primeras letras de Los Beatles como I wanna hold your hand o Ticket to ride. En el video también se puede notar, al menos en la vestimenta, un toque Beach Boys.

También reconozcamos que hablar de mandar una carta y que me vuelva al otro día con dirección desconocida es un poco lento, digamos desactualizado, aunque conserva su toque romántico.

A modo de humorada me permití adaptarla más a estos tiempos y con un toque de bajo nivel técnico. Que lo disfruten !!

Message returned
Message returned

I gave an e-mail to Postfix,
He put it in his queue.
Bright in early next second,
He brought my e-mail back.

It wrote upon it:
Message returned, address unknown.
No such domain, no such username.

We had a quarrel, a Facebook like
I write I'm sorry but my e-mail keeps coming back.

So then I send it to Postfix
And sent it special D.
Bright in early next second
It came right back to me.

It wrote upon it:
Message returned, address unknown.
No such domain, no such username.

This time I'm gonna take it myself
And will use SMTP.
And if it comes back the very next second
Then I'll understand the writing on it

Message returned, address unknown.
No such domain, no such username.

Message returned
Message returned
Message returned
Message returned

Smalltalk fileout conversion to simple text (fileout2txt)

2014-10-13T18:24:00.001-03:00

Working on some Smalltalk piece of code, the Pharo flavor, needed to put it into some report. Tried a code Fileout but on report insertion all sort o marks and signals show an ugly result. Because the code was several kilobytes long doing a HAND crafted reformat was not a choice then a file inspection gave me some clues.

The most annoying part was that between classes a new page was inserted then inspecting the file with hexdump show me that a simple 0x0c character was the cause of this behaviour

# hd Fileout.st

. . .

00004f10 6d 65 6e 74 53 74 61 6d 70 3a 20 27 3c 68 69 73 |mentStamp: '<his|

00004f20 74 6f 72 69 63 61 6c 3e 27 20 70 72 69 6f 72 3a |torical>' prior:|

00004f30 20 30 21 0d 21 0d 0d 0c 0d 46 6f 74 6f 59 6f 70 | 0!.!....FotoYop|

00004f40 45 78 63 65 70 74 69 6f 6e 20 73 75 62 63 6c 61 |Exception subcla|

. . .

To get rid of it a simple cat Fileout.st | tr -d \\014 was enough.

We also get some exclamation marks that are annoying too but they were discarded by using sed

sed -i 's/!//gm' Fileout.st

Now is the comments turn. They are internal comments and timestamps to wipe them out. grep and sed came to the rescue

cat Fileout.st | grep -v commentStamp: | sed 's/stamp: .*//'

Finally some dashed lines that seems to be used as separators arre also deleted

grep -v "\-\- \\--" Fileout.st

The basic bits were exposed here but there's a fully functional script you can use for conversion automation.

Enjoy !

Random tests, a random choice ?

2014-09-18T18:17:00.000-03:00

As a child I used to make a lot of random choices about on what path to follow for walking or to solve some issue and more often that not it lead me not only to the unknown but also to places where I wasn't supposed to arrive.

Reading about some tips for Unit Testing here and there I found myself trapped between two contradictory positions on testing about using random values and found myself in a revival of my childhood. The former guideline establishes that

When the boundary cases are covered, a simple way to improve test coverage further is to generate random parameters so that the tests can be executed with different input every time.

while the latter is emphatic against its practice

Another “practice” that must be avoided is writing tests with random input. Using randomized data in a unit test introduces uncertainty. When that test fails, it is impossible to reproduce because the test data changes each time it runs.

I'm more in favor of using random values but let me explain my position here.

To start with let me say that both positions make sense because to cover all test cases would be nice to cover all input values but this becomes impossible quickly. One idea should be to implement a sequential test space search in a way that after a lot of test runs there's a faint probability that an obscure corner case shows up and enlightens our code. The problem is that making the test aware saving where it stopped testing to resume it's execution later is a clear violation of the principle that no test must depend on other test outcome. Can be said that one test depending on itself is not a violation to this principle but if we think about test instances clearly the same test run with two different sets of inputs are two different test instances.

To avoid test dependency between test instances lets use random inputs, even this choice improves the namespace coverage. Using sequential namespace coverage makes the input equivalent classes traversal quite slow because each class is covered completely before going to the next one thus making error discovery only on move from one equivalent class to the next [1] (let's say that one class element is representative enough for the whole class and upon using it proves the whole class is right or wrong). Instead using random inputs means that more than one equivalent class is tested on each test execution thus producing a higher coverage ratio (classes visited / test execution) [2].

Going with the article stating against using random values for testing let's say that the uncertainty exists because there's no way to obtain the same data again because it's random (got it ?).

The flaw about the last assertion is that the article speaks about unit testing and according to agile practices once a test fails it's immediately fixed and is not left in oblivion waiting for a lack of failure the next time it runs. Showing the failure, the expected and obtained values should be enough to start a new equivalence class discovery, create a new test and fix that buggy code.

Returning to my random choices as a child I wish to use some bread crumbs to signal the way back home and not to worry my parents the way I did.

Some math rant

Regarding [1] let me demonstrate that the first part ("each class is covered completely before going to the next one") is not completely true unless you plan it carefully. Let's take a sum(int, int) method where the class equivalence boundary is where numbers change sign, then there's 4 equivalence classes 1) add positive number to positive number, 2) positive to negative, 3) negative to positive and 4) negative to negative). Let's run the test doing a complete scan :

for ( int a = -10, a <= 10; a++ )
for ( int b = -10, b <= 10; b++ )

assert a+b == sum(a,b)

in this test case equivalence classes are not completely exhausted before moving to the next one but alternating bit of 4) and a bit of 3) execution until exhaustion, then a bit of 1) and a bit of 2) until exhaustion. To do complete exhaustion before moving to the next one :

// Equivalence class 1
for ( int a = 0, a <= 10; a++ )
for ( int b = 0, b <= 10; b++ )

assert a+b == sum(a,b)

// Equivalence class 2
for ( int a = 0, a <= 10; a++ )
for ( int b = -10, b <= 0; b++ )

assert a+b == sum(a,b)

// Equivalence class 3
for ( int a = -10, a <= 0; a++ )
for ( int b = 0, b <= 10; b++ )

assert a+b == sum(a,b)

// Equivalence class 4
for ( int a = -10, a <= 0; a++ )
for ( int b = -10, b <= 0; b++ )

assert a+b == sum(a,b)

In the previous test case can be said that move to the next equivalence class is done only once the current one is exhausted then statement [1] ("each class is covered completely before going to the next one thus making error discovery only on move from one equivalent class to the next") applies, but in the first case (alternated equivalence class execution) the previous statement also holds true because doesn't matter that one equivalence class is exhausted but that a new one test starts because exercising just one equivalence class case and make it fail is enough to declare the complete equivalence class fails, then [1] holds true not because both parts are true (complete one and exercise the next) but because we can move from one equivalence class to another without exhaustion then testing just one case of the equivalence class is enough, thus identifying them and run one case test for each is enough to cover them all meaning that random testing is pointless because the same points of each equivalence class can be tested every time a test is run.

assert 12 == sum(8,4)

assert -4 == sum(-8,4)

assert 4 == sum(8,-4)

assert -12 == sum(-8,-4)

Not so. Doing some equivalence with bugs we do not know in advance how many equivalence classes exist and even when a code analysis is performed and equivalence classes are discovered cannot completely be sure that some hidden equivalence class exists or not, then executing one test case for each known equivalent class may led us to miss the hidden one(s). This is where random testing makes sense because selecting the test values at random there's a greater than zero possibility of discovering the hidden equivalence classes providing that random values are taken from a constant density distribution function meaning that the probability to hit the tiniest equivalence class (being just one combination of input parameters) is :

1
p = ----------------------------------------------------------------
param 1 space size * param 2 space size * ... param N space size

Please enjoy !

How to run Pharo 3.0 on top of Linux 64 bits

2014-09-02T16:24:00.001-03:00

As some of you guys I tried and failed, and found a lot of recipes on how make it work but it were just recipes, meaning that a minimal change and the recipe will turn useless. I will try to be a bit more generic here.

Just to start let me tell you that I am currently using Linux MINT but the solution should apply for every Debian based Linux distribution. The same concepts apply for other non-Debian distribution but the command to be executed to install new packages, and even the package names, are different.

Basically after Pharo download and expansion in its destination folder, the first error pops up :

./pharo: line 34: bin/pharo: No such file or directory

It's not that the file wasn't there but pharo binary was compiled for 32 bits. Sadly there's no Pharo 64 bits version (yet?).

To let the Pharo 32 bits compiled binary run on top of a 64 bits Linux the corresponding 32 bits libs must be installed. To verify it :

bin/pharo: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=f31881d89065e94ca3adbfca155f2b178ee8923b, not stripped

Then let's take a look at what libraries does bin/pharo needs :

$ ldd bin/pharo

not a dynamic executable

Seems there's a problem with ldd magic if the 32 bits libs are not installed. Let's do it :

sudo aptitude install lib32z1 lib32ncurses5 lib32bz2-1.0

After this install there's no missing libs for pharo executable

$ ldd bin/pharo
linux-gate.so.1 (0xf774c000)
libm.so.6 => /lib32/libm.so.6 (0xf76f1000)
libdl.so.2 => /lib32/libdl.so.2 (0xf76ec000)
libpthread.so.0 => /lib32/libpthread.so.0 (0xf76d1000)
libc.so.6 => /lib32/libc.so.6 (0xf7521000)
/lib/ld-linux.so.2 (0xf774d000)

but on startup a different error is thrown :

$ ./pharo

could not find module vm-display-X11

Aborted

There's a file named vm-display-X11 inside the bin folder than happens to be a 32 bits ELF executable binary dynamically linked. Let's check its dependencies :

$ ldd bin/vm-display-X11
linux-gate.so.1 (0xf7727000)
libpthread.so.0 => /lib32/libpthread.so.0 (0xf76d9000)
libGL.so.1 => not found
libX11.so.6 => not found
libc.so.6 => /lib32/libc.so.6 (0xf7529000)

/lib/ld-linux.so.2 (0xf7728000)

Lets' install the X11 stuff

sudo aptitude install libx11-6:i386

and check again

$ ldd bin/vm-display-X11

linux-gate.so.1 (0xf771a000)

libpthread.so.0 => /lib/i386-linux-gnu/libpthread.so.0 (0xf76cb000)

libGL.so.1 => not found

libX11.so.6 => /usr/lib/i386-linux-gnu/libX11.so.6 (0xf7592000)

libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xf741d000)

/lib/ld-linux.so.2 (0xf771b000)

libxcb.so.1 => /usr/lib/i386-linux-gnu/libxcb.so.1 (0xf73fb000)

libdl.so.2 => /lib/i386-linux-gnu/libdl.so.2 (0xf73f6000)

libXau.so.6 => /usr/lib/i386-linux-gnu/libXau.so.6 (0xf73f2000)

libXdmcp.so.6 => /usr/lib/i386-linux-gnu/libXdmcp.so.6 (0xf73eb000)

Now it's time for libGL :

sudo aptitude install libgl1-mesa-glx:i386

And finally I'm happy because ... Pharo is working on my 64 bits Linux !!!!

Cómo encarar un TP

2014-08-10T19:58:00.002-03:00

Síntesis

Lo que quiero mostrar en este post es cómo hacer que tu tiempo de programación te rinda, básicamente puntualizando lo que tenés que hacer, realizando pequeños cambios en el código por vez y probar estos cambios.

Puntualizar las tareas a hacer

Voy a empezar con una anécdota sobre lo que me pasó cursando la materia Sistemas Operativos. En una clase nos encomendaron una tarea y básicamente a la clase siguiente entregué un pequeño programa y un detallado informe de cómo funcionaba, pero pasó que no era exactamente lo que yo había hecho lo que se pedía, simplemente había empezado con lo pedido, dejé volar mi imaginación y terminó como terminó. El primer error fue no anotar, pormenorizar y atenerme al pedido.

Para ejemplificar vamos a tomar el TP1 del primer cuatrimestre de la materia Algortimos 2 para Electrónicos (Faculta de Ingeniería, UBA) :

Línea de comandos

implementar opción -i que indique el archivo/stream de entrada (default: stdin)
implementar opción -o que indique el archivo/stream de salida (default: stdout)
pasando como parámetro "-" indica stdin o stdout
el orden de las opciones es irrelevante, pueden venir en cualquier orden

Valor de retorno

nulo en caso de terminar bien
no nulo en caso de terminar mal

Salida

Si termina mal debe mostrar "error: " má una descripción del mismo
Si termina bien consta de una secuencia de líneas con información del archivo de entrada (ver punto 5.2 del enunciado)

Entrada

No puede haber líneas vacías
Cada línea consta de 1 comando y 1 o 2 parámetros (ver punto 5.1 para formato de cada comando)

En realidad hay algunas cosas más que podrían anotarse, pero para muestra nos alcanza esto. Notar que esto es sólo una lista de tareas a realizar pero los detalles específicos (formatos, etc. ) no son colocados para 1) poder tener en un vistazo de qué hicimos y cuánto falta por hacer y 2) no cometer errores de transcripción al copiarlo del enunciado a nuestra lista

Cómo probar los cambios

Un tiempo después de cursar Sistema Operativos cursé Matemática Discreta y tenía un TP que funcionaba pero había que arreglar 2 o 3 cosas, así que en la devolución de la segunda entrega para mi sorpresa algo que funcionaba había dejado de funcionar y tuve que invertir aún más tiempo en hacer algo que ya había hecho, pero que se había roto.

En principio cada vez que se codifica normalmente se prueba invocando el programa, se determina que funciona y se continúa con la siguiente parte del código. En principio todo funciona, pero este plan tiene un par de fallas 1) qué pasa si más adelante esto deja de funcionar ? cómo darse cuenta del problema ? y 2) por qué código de más, previo a ejercitar el código que se quiere probar, sólo para saber que una parte de este sigue funcionando ?

Para estos dos puntos la respuesta, en principio, es testing y programación orientada a objetos. En honor a la verdad no es absolutamente necesario programar con orientación a objetos pero lo hace muy conveniente a la hora de hacer testing ya que al dividir las distintas partes del código en unidades autosuficientes (o algo similar) permite poder probar sólo el código necesario.

Para empezar hay que hacer que en "Cada línea consta de 1 comando y 1 o 2 parámetros" así es que se hace una clase que reciba una línea y diga si no responde a esta estructura y en caso de responder cuál es el comando, cuáles sus parámetros. Para esto se propone la siguiente clase :

class LineParser {
private:
string line;
string command;
vector<string> *params;
public:
LineParser(const string );
LineParser(const LineParser & );
virtual ~LineParser();
void parse();
string getCommand() const;
vector<string> * getParams() const;
};

y abstrayéndonos de su implementación vamos a probar que funcione como necesitamos. En principio se puede probar :

pasar una línea con 1 comando y 1 argumento
pasar una línea con 1 comando y 2 argumentos

y probar que en cada una de estas me devuelva el resultado correcto (en el primero que me devuelva 1 argumento y en el segundo que me devuelva 2 argumentos). A cada uno de estas pruebas se las llama casos de prueba.

Para implementar estos casos de prueba vamos a usar una lib especializada para hacer testing que se denomina cpptest. En esta cada caso de prueba se implementa como un método de una clase codificada en C++ y estos métodos se agrupan en una clase denominada test suite.

Pero mejor veamos un ejemplo :

void LineParserTestSuite::comandoParametro() {

LineParser lp("AAAA bbbbb");

lp.parse();

TEST_ASSERT_EQUALS("AAAA", lp.getCommand());

vector<string> *p = lp.getParams();

TEST_ASSERT_EQUALS(1, p->size());

TEST_ASSERT_EQUALS("bbbbb", (*p)[0]);

}

void LineParserTestSuite::comando2Parametros() {

LineParser lp("AAAA bbbbb ccc");

lp.parse();

TEST_ASSERT_EQUALS("AAAA", lp.getCommand());

vector<string> *p = lp.getParams();

TEST_ASSERT_EQUALS(2, p->size());

TEST_ASSERT_EQUALS("bbbbb", (*p)[0]);

TEST_ASSERT_EQUALS("ccc", (*p)[1]);

}

Como se puede ver básicamente se trata de crear el objeto correspondiente, llamar a los métodos correspondientes en el orden adecuado (en este caso el método parse() ), obtener el resultado ( getParams() ) y verificar que el valor obtenido sea el esperado. Este último paso se hace a través de un assert (aserción) y que si el resultado no es el esperado entonces se nos lo hace saber a través de un error.

Comentarios finales

Este post es sólo una visión muy por arriba y probablemente hay un millón de dudas sobre cómo realmente hacer para probar y demás, así que para ver este ejemplo funcionando ejecutar :

# git clone https://github.com/bit-man/input-generator-a2.git && cd tp-sample/src/test/ && make clean test && ./tests.exe

...

LineParserTestSuite: 7/7, 100% correct in 0.000109 seconds

Total: 7 tests, 100% correct in 0.000109 seconds

y como se puede ver en las líneas finales se ejecutaron 7 tests de 7 y todos terminaron bien. El código de LineParser se puede verlo en el directorio src y el código de test en src/test.

The Daily Nerd, blog edition no more (?)

2014-06-05T15:05:00.001-03:00

The Daily Nerd (blog, news, etc.) is an continuous running experiment that has become an extension of my daily activities, and as a such it suffers/benefits from it.

Lately I've been very focused in activities, such as studying, that allowed me to gain insight in some tech topics but require extra time effort. This made me work a bit harder on time efficiency. I've learned that is easier for me to publish each article that I found interesting as is read even that collect them in a single blog entry, do some editing and publish in block as The Daily Nerd edition.

For some time I'll continue in this path and no more blogs entries tagged Daily Nerd News will be generated, instead you can follow me on Twitter, Google+ or Pinterest if still want to receive updates on what I read on a daily basis. Of course I'll shift focus towards blog entries for topics I continue learning and researching (e.g. OSGi series).

Thanks for watching and stay tuned!

The Daily Nerd (May 22nd, 2014)

2014-05-22T18:08:00.002-03:00

Thorium: the wonder fuel that wasn't

“Thorium-Fueled Automobile Engine Needs Refueling Once a Century,” reads the headline of an October 2013 story in an online trade publication. This fantastic promise is just one part of a modern boomlet in enthusiasm about the energy potential of thorium, a radioactive element that is far more abundant than uranium. Thorium promoters consistently extol its supposed advantages over uranium. News outlets periodically foresee the possibility of "a cheaper, more efficient, and safer form of nuclear power that produces less nuclear waste than today's uranium-based technology."

Guest Post: No turning back, NASA ISEE-3 Spacecraft Returning to Earth after a 36 Year Journey

The International Sun-Earth Explorer spacecraft (ISEE-3) is phoning home and will be returning whether we are ready or not. Launched in 1978 to study Earth’s magnetosphere, the spacecraft was later repurposed to study two comets. Now, on its final leg of a 30-plus year journey to return to Earth, there’s a crowdfunding effort called ISEE-3 Reboot aimed at reactivating the hibernating spacecraft since NASA is not offering any funding to do so.

Quantum Random Number Generator Created Using A Smartphone Camera

One of the hidden foundations of modern life are random numbers. If you make credit card payments over the internet, for example, you’re a serial user of random numbers which are necessary to guarantee the security of your personal details.

And with the advent of techniques such as quantum cryptography, which guarantees perfect secrecy and requires vast quantities of random numbers, the demand for these mathematical objects is set to increase dramatically.

The Daily Nerd (May 6th, 2014)

2014-05-06T17:58:00.000-03:00

Echoes of Chelyabinsk: Another Fireball Explodes Over Russia

Why does Russia seem to get so many bright meteors? Well at 6.6 million square miles it’s by far the largest country in the world plus, with dashboard-mounted cameras being so commonplace (partly to help combat insurance fraud) statistically it just makes sense that Russians would end up seeing more meteors, and then be able to share the experience with the rest of the world!

Pingpong! How You Could Send Something Small High In The Atmosphere

Spring is a time of treasures in eggs — think about the Easter weekend that just passed, for example, or the number of chicks hatching in farms across the world. That’s also true of “near-space” exploration. A project called PongSats has sent thousands of tiny experiments into space, and is ready to send up another batch this coming September.

The concept is simple for the students participating — slice open a ball, put something inside you want to test at high experiments, then repackage it and decorate
it for the big trip up. The balloons will soar to about 19 miles (30 kilometers), which is well below the Karman Line of 62 miles or 100 kilometers that marks the edge of space. Don’t discount that, however — you will still see black skies and the curvature of the Earth from that altitude.

Ancient Martian Life May Be Preserved in Glass

When large asteroids or comets strike the Earth — as they have countless times throughout our planet’s history — the energy released in the event creates an enormous amount of heat, enough to briefly melt rock and soil at the impact site. That molten material quickly cools, trapping organic material and bits of plants and preserving them inside fragments of glass for tens of thousands, even millions of years.

Researchers studying impact debris on Earth think that the same thing could very well have happened on Mars, and that any evidence for ancient life on the Red Planet might be found by looking inside the glass.

Bye bye Ubuntu, hello Linux Mint Debian

2014-04-25T17:52:00.001-03:00

After 5 or 6 years of using Ubuntu I am letting it go. Sort of.

I felt quite comfortable with it until one or two years ago they moved to Unity and the wind of change began blowing and sooner than later the hurricane warning widespread. With disrespect signals going back and forth you gain no friends.

I will not reproduce here the plethora of controversial decisions Canonical has taken but tell you about how I decided the move to Linux Mint Debian.

Lot of users == lot of problems solved earlier

Seems to be an old truth but being it as old as computing is not usually taken into account by tech savvy people like me, and using Linux in all machines I own and work (from phone to home desktop and work desktop machine) being able to find solution to almost any problem in a breeze is my primary concern, mostly when you spend all you working day atop of a machine programming, reading Internet articles or even e-mail reading. Minimum disruption and short delays for solution search and problem solving is highly desirable.

Same thing can be said about security. Is not an admin server concern anymore (should I repeat Hearthbleed bug three times for something horrible to happen?) but being connected to the Internet at all times (at home and at work) makes myself also responsible for my own security, meaning updating to any product safe version as soon as a security alert is widespread, security related configuration changes, etc.

Debian derivative != Ubuntu derivative

The idea that drive this change, as explained earlier, is to punish Canonical about the wrong decisions taken regarding the Open Source movement. Being said that an Ubuntu based distribution is out of scope

Programming language of choice (am I tied to my old OS?)

I currently program in Java, Shell Script and some C++ (mainly for fun) and the three of them can be used/programmed in any Linux environment. My current IDE choices are IntelliJ for Java/Shell Scripting and Eclipse for C++ meaning that I'm not tight coupled to any desktop OS. Also I'm a big fan of jEdit.

Android OS is a very different kind of animal to talk about. Some time ago I needed to change my aging laptop and being a tech aware boy as I am tried an innovative approach by buying a powerful and extensible tablet with Android that can be used as a desktop and as a tablet, but because of not being able to use neither IntelliJ nor Eclipse (or any other Java program because of SWT or Swing to being ported to Android) I have to abort that lovely project. Poor of me :-(

Hardware performance in the era of commodity hardware

Unless you need very tight spec about the hardware to use or need an exorbitant quantity of memory, disk capacity, speed or massive CPU usage there's no need to go further into this point. Anything that I was able to run with Ubuntu, in terms of performance, surely will be able to run also in any other Linux distro. No special requirements here from my side.

VMs and how choosing your OS became easier

Because I'm in a full production environment can't take a full time week or so to decide which OS to move to, then using a Virtual Machine was a huge bonus.

The basic idea behind this was to install a VM with the candidates OSes and my daily usage apps, trying it for some time (usually a couple of days) and using my core apps to interact with other persons and effectively being able to do my work.

I was not in the high risk zone here because of moving into an arena that is based on Linux and Java then have no problems in any of the solutions tested

UI matters, or not ?

Not for me. I'm not a huge fan of UI beyond its basic usage. Don't get me wrong I really appreciate all the hard work UI guys put on it but at the moment, to put a well known example, Gnome 3 has no real advantage for me because the way I work. That's a huge advantage for me because I can stick to Gnome 2 or basic Xfce functionality without any extra suffering. May be I'm missing something about top notch UIs that I've not discovered yet (I must confess that I'm delighted about touch screen oriented UIs)

Conclusion

Ubuntu so long and thanks for all the fish. Long life to Linux Mint Debian distribution.

The Daily Nerd (April 16th, 2014)

2014-04-16T15:03:00.002-03:00

Follow-Up on Skydiving Meteorite: Crowdsourcing Concludes it Was Just a Rock

For all those involved with the initial investigation of the skydiver and the possible meteorite, they now feel they have resolution to their puzzle, thanks to the beauty of crowdsourcing. The rock that showed up in a video taken during a skydive in Norway in 2012 was likely just a rock — accidentally packed in the parachute — and not a meteoroid.

Steinar Midtskogen, from the Norwegian Meteor Network who was involved in the initial investigation of the video, suggested an adaptation of Linus’s Law to explain what has happened in the past week: “Given enough eyeballs, all mysteries are shallow.”

¿Un Walkman? ¿Y eso que es?

Eso es lo que aparentemente se preguntan los chicos de las nuevas generaciones, ante ese preciado objeto que soliamos exhibir con orgullo en la decada de los 80 y principios de los 90s. Señoras, y señores, así reaccionan los purretes cuando ven un ¡WALKMAN!

Tecnología y no tanto: Movibug

Descubrí un bug (comportamiento no esperado en una aplicación) de seguridad en movistar. Me parece que lo mejor que puedo hacer es compartirlo para que sea de público conocimiento. La primera vez que lo vi fue en enero y sigue en vigencia.

New Gully Appears On Mars, But It’s Likely Not Due To Water

Check out the groove! In the blink of a geological lifetime, a new gully has appeared on the planet Mars. These images from NASA’s Mars Reconnaissance Orbiter show a new channel in the southern hemisphere region of Terra Siernum that appeared between November 2010 and May 2013.

While there’s a lot of chatter about water on Mars, this particular feature is likely not due to that liquid, the agency added.

The GNOME Foundation Is Running Out of Money

The GNOME Foundation is running out of money. The foundation no longer has any cash reserves so they have voted to freeze non-essential funding for running the foundation. They are also hunting down sponsors and unpaid invoices to regain some delayed revenue. Those wishing to support the GNOME Foundation can become a friend of GNOME.

The Daily Nerd (April 11th, 2014)

2014-04-11T18:43:00.001-03:00

Serious OpenSSL bug renders websites wide open

A serious vulnerability in the popular OpenSSL cryptographic library has been discovered that allows attackers to steal information unnoticed.

Known as the Heartbleed bug, the vulnerability allows anyone on the Internet to read the memory of systems that run vulnerable versions of OpenSSL, revealing the secret authentication and encryption keys to protect the traffic.

User names, passwords and the actual content of the communications can also be read.

50 years ago, IBM created mainframe that helped send men to the Moon

System/360 machines were crucial for NASA's Apollo missions. "Apollo flights had so much information to relay, that their computers had to report in an electronic form of shorthand," IBM says. "Even in shorthand, however, it took a circuit capable of transmitting a novel a minute to get the information to NASA’s Manned Spacecraft Center—now the Johnson Space Center—in Houston, Texas. Receiving this enormous amount of data was a powerful IBM computer whose sole task was to translate the shorthand into meaningful information for Apollo flight controllers. The IBM System/360 computer absorbed, translated, calculated, evaluated, and relayed this information for display. It was one of five System/360 machines used by NASA for the Apollo 11 mission. The same System/360 computer that processed the data for the first lunar landing from 240,000 miles away in Houston also calculated the liftoff data needed by astronauts Neil Armstrong and Edwin 'Buzz' Aldrin to rendezvous back with the command module piloted by Michael Collins for the flight back to Earth."

Could This Be The Signal Of Dark Matter? Unsure Scientists Checking This Out

Sometimes a strange signal comes from the dark and it takes a while to figure out what that signal means. In this case, scientists analyzing high-energy gamma rays emanating from the galaxy’s center found an unexplained source of emission that they say is “consistent with some forms of dark matter.”

The data came courtesy of NASA’s Fermi Gamma-ray Space Telescope and was analyzed by a group of independent scientists. They found that by removing all known sources of gamma rays, they were left with gamma-ray emissions that so far, they cannot explain. More observations will be needed to characterize these emissions, they cautioned.

The Daily Nerd (April 8th, 2014)

2014-04-08T16:59:00.001-03:00

Tesla Model S Ethernet Network Explored, Possible Jailbreak in the Future?

While we’re testing the performance capabilities of the Tesla Model S by running it down the 1/4 mile in heads up races such as Tesla vs Corvette Stingray and Tesla vs Viper, others are digging deep into how the Tesla Model S functions internally.

Being the technical marvel that the Model S is with it’s 17″ multi-touch display, all digital dashboard, all electric drivetrain, remote control Apps and more, along with the fact that the car was designed from the ground up with no predecessor, it’s no surprise that internally it’s using the latest technologies to run these systems.

CERF: Classified NSA Work Mucked Up Security For Early TCP/IP

Curiously enough Cerf revealed that he did have access to some really bleeding edge cryptographic technology back then that might have been used to implement strong, protocol-level security into the earliest specifications of TCP/IP. Why weren’t they used, then? The culprit is one that’s well known now: the National Security Agency.

Cerf told host Leo Laporte that the crypto tools were part of a classified project he was working on at Stanford in the mid 1970s to build a secure, classified Internet for the National Security Agency.

Norwegian Skydiver Almost Gets Hit by Falling Meteor

It sounds like a remarkable story, almost unbelievable: Anders Helstrup went skydiving nearly two years ago in Hedmark, Norway and while he didn’t realize it at the time, when he reviewed the footage taken by two cameras fixed to his helmet during the dive, he saw a rock plummet past him. He took it to experts and they realized he had captured a meteorite falling during its “dark flight” — when it has been slowed by atmospheric braking, and has cooled and is no longer luminous.

When The Internet of Things Attacks! Parsing The IoT Botnet Story

I spent most of last week at a conference in Florida going deep on the security of critical infrastructure – you know: the software that runs power plants and manufacturing lines. (More to come on that!) While there, the security firm Proofpoint released a statement saying that it had evidence that a spam botnet was using “Internet of Things” devices.

The company said on January 16 that a spam campaign totaling 750,000 malicious emails originated with a botnet made up of “more than 100,000 everyday consumer gadgets” including home networking routers, multi media centers, televisions and at least one refrigerator.” Proofpoint claims it is the “first time the industry has reported actual proof of such a cyber attack involving common appliances.”

The Daily Nerd (April 4th, 2014)

2014-04-04T18:07:00.001-03:00

The Astounding Link Between the P≠NP Problem and the Quantum Nature of Universe

With some straightforward logic, one theorist has shown that macroscopic quantum objects cannot exist if P≠NP, which suddenly explains one of the greatest mysteries in physics

Deep Ocean Detected Inside Saturn's Moon

NASA's Cassini spacecraft and Deep Space Network have uncovered evidence that Saturn's moon Enceladus harbors a large underground ocean, furthering scientific interest in the moon as a potential home to extraterrestrial microbes.

Researchers theorized the presence of an interior reservoir of liquid water in 2005 when Cassini discovered water vapor and ice spewing from vents near the moon's south pole. New data on the moon's gravity field reported in the April 4, 2014, edition of the journal Science strengthen the case for an ocean hidden inside Enceladus.

Vint Cerf: CS Changes Needed To Address IoT Security, Privacy

The Internet of Things has tremendous potential but also poses a tremendous risk if the underlying security of Internet of Things devices is not taken into account, according to Vint Cerf, Google’s Internet Evangelist.

Cerf, speaking in a public Google Hangout on Wednesday, said that he’s tremendously excited about the possibilities of an Internet of billions of connected objects, but said that securing the data stored on those devices and exchanged between them represents a challenge to the field of computer science – and one that the nation’s universities need to start addressing.

The Daily Nerd (March 3rd, 2014)

2014-04-03T15:18:00.003-03:00

Gunshot victims to be suspended between life and death

Doctors will try to save the lives of 10 patients with knife or gunshot wounds by placing them in suspended animation, buying time to fix their injuries

NEITHER dead or alive, knife-wound or gunshot victims will be cooled down and placed in suspended animation later this month, as a groundbreaking emergency technique is tested out for the first time.

Chris Granger - Toward a better programming

When I built the original prototype of Light Table I didn't have any grand purpose or goal in mind. I simply had some ideas on how programming could be better and I wanted to see how hard they would be to build. Until fairly recently, it never dawned on me that I've actually spent the past decade trying out ideas on how programming could be better, from web frameworks, to Visual Studio, to Light Table and its future. And it wasn't until I had that realization that I also came to the conclusion that I'd been going about this all wrong. As a matter of fact, I made a classic rookie mistake: I set out to answer a question I didn't understand.

George Lucas explains how he invented lightsabers

Birth of the Lightsaber was first seen as a special feature on the original Star Wars trilogy's DVD boxset in 2004, but this marks the first time the video has made its way onto the internet in an official capacity. It tells how Star Wars' production staff planned and choreographed the movies' increasingly complex fight sequences, and how they came to understand the capabilities and limitations of Lucas' invented weapon. There's one particularly interesting shot around two minutes into the video that shows Obi Wan Kenobi being run through by Darth Vader's lightsaber. In Lucas' cut of Episode IV, the blade passes through an ethereal Obi Wan; in the early shot, it rips through his cloak, leaving a trail of fire and the aging Jedi's upper body hanging in the air as his lower body slumps to the floor.

Shutting down Ubuntu One file services

Today we are announcing plans to shut down the Ubuntu One file services. This is a tough decision, particularly when our users rely so heavily on the functionality that Ubuntu One provides. However, like any company, we want to focus our efforts on our most important strategic initiatives and ensure we are not spread too thin.

The Daily Nerd (March 28th, 2014)

2014-03-28T16:18:00.002-03:00

Millions of Android app downloads infected with cryptocoin-mining code

Researchers at security company Trend Micro say they have found at least two apps on the Google Play store, Songs and "Prized", which contain code to join any phone that has them to a cryptocoin-mining "pool". Each app has had between 1m and 5m downloads, meaning that up to 10m phones might be affected. Songs was still available at the time of publication. An email to the developer had not been answered by time of publication.

Peter Molyneux: He reveals some interesting insights from his period while working at Microsoft

I left Microsoft because I think when you have the ability to be a creative person, you have to take that seriously, and you have to push yourself. And pushing yourself is a lot easier to do if you’re in a life raft that has a big hole in the side, and that’s what I think indie development is. You’re paddling desperately to get where you want to go to, but you’re also bailing out. Whereas if you’re in a big supertanker of safety, which Microsoft was, then that safety is like an anesthetic. It’s like taking antidepressants. The world just feels too comfortable.

Ubuntu and the Unspoken Rules

The conflicts between Ubuntu and its commercial counterpart Canonical on the one hand and other free software projects on the other hand are not just about Unity, the wording of the Canonical Contributors' License Agreement, the technical differences between Mir and Wayland, or any of the half dozen other issues being so passionately discussed at any given time.

Contrary to what Ubuntu supporters sometimes claim, the conflict has little to do with jealousy. After all, Canonical has yet to turn a profit, and has had its share of failures, such as the Ubuntu Edge crowdfunding campaign.

Building PRISM-Proof Web Services

Reminders that data entrusted to online services can easily be leaked or stolen aren’t hard to find. Major companies commonly have passwords and other data taken by attackers, while governments have their own ways to get hold of user data.

Researcher Raluca Popa of MIT thinks many online services should and could be redesigned to guard against that. “Really, there’s no trusting a server,” she says. Popa has led the development of a system called Mylar for building Web services that puts that philosophy into practice. Services built using it keep data on their servers encrypted at all times and only ever decrypt it on a person’s computer.

The Daily Nerd (March 21st, 2014)

2014-03-21T18:42:00.002-03:00

How Engineers Are Building a Power Station At the South Pole

If you had to choose the most difficult place in which to build a power station, the South Pole would probably come close to the top of your list. During the winter, the station and the 40 or so people who overwinter there, are entirely isolated. Power comes from three generators burning JP-8 jet fuel which has to be flown in during the summer at considerable cost.

But the South Pole is also home to an increasing number of ambitious experiments. The most famous is probably the Icecube Neutrino Observatory, which peers through a cubic kilometre of ice beneath the pole, looking for the tell-tale flashes generated by high energy neutrinos. This has its own set of generators that power the detectors and their associated electronics.

But researchers are currently building an even bigger experiment called the Askaryan Radio Array that will search for neutrinos in a volume of ice thousands of times larger than Icecube.

A Startlingly Simple Theory About the Missing Malaysia Airlines Jet

There has been a lot of speculation about Malaysia Airlines Flight 370. Terrorism, hijacking, meteors. I cannot believe the analysis on CNN; it’s almost disturbing. I tend to look for a simpler explanation, and I find it with the 13,000-foot runway at Pulau Langkawi.

We know the story of MH370: A loaded Boeing 777 departs at midnight from Kuala Lampur, headed to Beijing. A hot night. A heavy aircraft. About an hour out, across the gulf toward Vietnam, the plane goes dark, meaning the transponder and secondary radar tracking go off. Two days later we hear reports that Malaysian military radar (which is a primary radar, meaning the plane is tracked by reflection rather than by transponder interrogation response) has tracked the plane on a southwesterly course back across the Malay Peninsula into the Strait of Malacca.

How Lithium-Ion Batteries Age: Scientists Offer Insight

Aging is a part of life, even for lithium-ion batteries.

And battery life is an important consideration for electric-car owners, especially in these early days before there's sufficient real-world data on actual life of electric-car battery packs over the 10- or 15-year lifespan of a typical vehicle.

Just like any other car part, batteries degrade over time, and so does their ability to hold a charge.

The Daily Nerd (March 19th, 2014)

2014-03-19T15:44:00.003-03:00

Operation Windigo: Linux malware campaign that infected 500,000 Computers Worldwide

In late 2013, Security Researchers identified thousands of Linux systems around the world infected with the OpenSSH backdoor trojan and credential stealer named Linux/Ebury, that allows unauthorized access of an affected computer to the remote attackers.

Antivirus Firm ESET's Reseacher team has been tracking and investigating the operation behind Linux/Ebury and today team uncovers the details of a massive, sophisticated and organized malware campaign called 'Operation Windigo', infected more than 500,000 computers and 25,000 dedicated servers.

Backdoor found in Samsung Galaxy Devices, allows Hackers to remotely access/modify Data

Google’s Android operating system may be open source, but the version of Android that runs on most phones, tablets, and other devices includes proprietary, closed-source components.

Phone makers, including Samsung ships its Smartphones with a modified version of Android, with some pre-installed proprietary software and because of lack in independent code review of those closed-source apps, it is complex to authenticate its integrity and to identify the existence of backdoors.

Big Bang, Inflation, Gravitational Waves: What It Means

On Monday, astronomers announced a profound discovery. Etched into the most ancient radiation that pervades the entire universe and created — literally — at the dawn of time, gravitational waves have been directly observed, giving us a glimpse as to the nature of the inflationary period that is theorized to have caused the rapid growth of our universe just after the Big Bang.

Finding further observational evidence for cosmic inflation should be discovery enough, but the fact that astronomers now have observational evidence for the existence of gravitational waves makes this St. Patrick’s Day a very special Red Letter Day for Cosmology.

The Daily Nerd (March 18th, 2014)

2014-03-18T17:16:00.002-03:00

Curso de Introducción a Apache OpenOffice 4.0

Curso de Introducción a la suite libre y gratuita Apache OpenOffice, en su versión 4.0. Se explica cómo descargar e instalar el paquete de ofimática, se da un vistazo rápido a los programas que contiene, se explica cómo mejorarlo mediante extensiones y plantillas, operaciones básicas con documentos, y por último se ofrecen algunos recursos de aprendizaje.

Sharing what’s up our sleeve: Android coming to wearables

Today we’re excited to extend Android to wearables. And we’re starting with the most familiar wearable—watches. We’re already working with several consumer electronics manufacturers, including Asus, HTC, LG, Motorola and Samsung; chip makers Broadcom, Imagination, Intel, Mediatek and Qualcomm; and fashion brands like the Fossil Group to bring you watches powered by Android Wear later this year. If you’re a developer, check out developer.android.com/wear to download a Developer Preview so you can tailor your existing app notifications for watches powered by Android Wear. Look out for more developer resources and APIs coming soon.

Big Bang's Smoking Gun Found

For the first time, scientists have found direct evidence of the expansion of the universe, a previously theoretical event that took place a fraction of a second after the Big Bang explosion nearly 14 billion years ago.

The clue is encoded in the primordial cosmic microwave background radiation that continues to spread through space to this day.

Scientists found and measured a key polarization, or orientation, of the microwaves caused by gravitational waves, which are miniature ripples in the fabric of space.

Pi Day

2014-03-14T14:26:00.000-03:00

Pi Day · Celebrate Mathematics on March 14th

Wikipedia says :

Pi Day is an annual celebration commemorating the mathematical constant π (pi). Pi Day is observed on March 14 (or 3/14 in the U.S. month/day date format), since 3, 1, and 4 are the three most significant digits of π in the decimal form.[...]

In the year 2015, Pi Day will have special significance on 3/14/15 at 9:26:53 a.m. and p.m., with the date and time representing the first 10 digits of pi.

Pi Approximation Day is observed on July 22 (or 22/7 in the day/month date format), since the fraction 22⁄7 is a common approximation of π.

How to Celebrate Pi Day

Pi is a mathematical constant that is the ratio of a circle's circumference to its diameter, and it is also one of the most revered mathematical constants in the known world. Pi Day was first officially celebrated on a large scale in 1988 at the San Francisco Exploratorium.Since then, Pi Day has been celebrated by millions of students and math-lovers. The holiday is celebrated on 14th March, since 3, 1, and 4 are the three most significant digits in the decimal form of pi. If you'd like to learn how to celebrate pi in due fashion, read on and it will be as easy as pi.

Happy Pi Day! It’s also Albert Einstein’ birthday

Today is March 14th, or 3/14. And that makes it Pi Day -- the day where math nerds across the country gather to eat pie and discuss the importance of numbers. But did you know it's also Albert Einstein's birthday? The theoretical physicist whose name has become synonymous with genius was born on March 14, 1879, in what was then the Kingdom of Württemberg in the German Empire.

The Daily Nerd (March 12th, 2014)

2014-03-12T15:23:00.001-03:00

Encryption Works: How to Protect Your Privacy in the Age of NSA Surveillance

The NSA is the biggest, best funded spy agency the world has ever seen. They spend billions upon billions of dollars each year doing everything they can to vacuum up the digital communications of most humans on this planet that have access to the Internet and and the phone network. And as the recent reports in the Guardian and Washington Post show, even domestic American communications are not safe from their net.

Defending yourself against the NSA, or any other government intelligence agency, is not simple, and it's not something that can be solved just by downloading an app. But thanks to the dedicated work of civilian cryptographers and the free and open source software community, it's still possible to have privacy on the Internet, and the software to do it is freely available to everyone. This is especially important for journalists communicating with sources online.

Audi's Traffic Light Recognition Tech Will Save You Gas, Time

Essentially, it relies on in-car internet to connect to the traffic systems in a town or city, at which point it can relay information to the driver on the cycle of the traffic lights ahead.

The idea is that if a light is changing ahead, the car already knows about it--and can suggest actions to the driver based on what the light will do next.

If you're approaching a light that's set to turn red before you reach it, for example, a message pops up in the instrument cluster suggesting you begin to slow down, rather than having to brake at the last minute when the lights change.

What 'Cosmos' Got Wrong About Giordano Bruno, the Heretic Scientist

The reboot paid tribute to its progenitor with a tear-jerking segment about Sagan's life and career (spoiler alert: dude was the best). But creators Neil deGrasse Tyson, Seth MacFarlane, and Ann Druyan also showed their respect by emulating many of the tropes and flourishes of the PBS series, like the visualization of a Cosmic Calendar and the use of a historical figure to support the larger themes of the episode. In the original pilot, Sagan showcased Hypatia of Alexandria as an example of a classic science martyr. In the reboot, Giordiano Bruno, the famed Italian cosmologist executed for heresy, was cast for that role.

New ozone-destroying chemicals found in atmosphere

Dozens of mysterious ozone-destroying chemicals may be undermining the recovery of the giant ozone hole over Antarctica, researchers have revealed.

The chemicals, which are also extremely potent greenhouse gases, may be leaking from industrial plants or being used illegally, contravening the Montreal protocol which began banning the ozone destroyers in 1987. Scientists said the finding of the chemicals circulating in the atmosphere showed "ozone depletion is not yesterday's story."

The Daily Nerd (March 10th, 2014)

2014-03-10T14:54:00.002-03:00

Video Acceleration Takes The Backseat On Chrome For Linux

Due to notorious Linux graphics drivers, Google developers working on Chrome/Chromium aren't looking to enable hardware video acceleration by default anytime soon. The problem ultimately comes down to poor Linux graphics drivers.

NASA Forgets How To Talk To ICE/ISEE-3 Spacecraft

The transmitters of the Deep Space Network, the hardware to send signals out to the fleet of NASA spacecraft in deep space, no longer includes the equipment needed to talk to ISEE-3. These old-fashioned transmitters were removed in 1999.' Could new transmitters be built? Yes, but it would be at a price no one is willing to spend. 'So ISEE-3 will pass by us, ready to talk with us, but in the 30 years since it departed Earth we've lost the ability to speak its language,' concludes Lakdawalla. 'I wonder if ham radio operators will be able to pick up its carrier signal — it's meaningless, I guess, but it feels like an honorable thing to do, a kind of salute to the venerable ship as it passes by.

Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

Your iPhone is more powerful than the evidence-collecting computers in the cockpit. Simple changes could mean faster answers for plane crashes

Why Airplane Black Boxes Fail

Why do we still rely on 1960s technology to rescue missing planes? In order to find and save flights like Malaysia Airlines' Flight 370, we must send data out in real-time.

Indeed, after the disappearance of Flight 447, an exasperated French investigator held aloft a cylinder the size of a small flashlight and said “This is what we are trying to find…in the Atlantic.” In that case it was a sonar beacon intended to lead searchers to a wreck, not the actual flight recorder which is neither black nor a box but about the size of a carry-on duffel.

The Daily Nerd (March 4th, 2014)

2014-03-04T18:13:00.002-03:00

Meet the seven people who hold the keys to worldwide internet security

It sounds like the stuff of science fiction: seven keys, held by individuals from all over the world, that together control security at the core of the web. The reality is rather closer to The Office than The Matrix

In a nondescript industrial estate in El Segundo, a boxy suburb in south-west Los Angeles just a mile or two from LAX international airport, 20 people wait in a windowless canteen for a ceremony to begin. Outside, the sun is shining on an unseasonably warm February day; inside, the only light comes from the glare of halogen bulbs.

Starting to Demo the Wolfram Language

The Wolfram Language is a highly developed knowledge-based language that unifies a broad range of programming paradigms and uses its unique concept of symbolic programming to add a new level of flexibility to the very concept of programming.

Chevron Gives Residents Near Fracking Explosion Free Pizza

After a Chevron hydraulic fracturing well exploded in rural Dunkard Township, Pennsylvania, last Tuesday, and burned for four days straight, the energy company knew just the way to soothe nearby residents: free pizza.

The flames that billowed out of the Marcellus Shale natural gas well were so hot they caused a nearby propane truck to explode, and first responders were forced to retreat to avoid injury. The fire burned for four days, and Chevron currently has tanks of water standing by in case it reignites. Of the twenty contractors on the well site, one is still missing, and is presumed dead.

With 'virgin' developers, Microsoft could fork Android

Windows Phone is not an option for Microsoft’s mobile renaissance. It’s just too little and too late.

To catch up, Microsoft could invest in an Android fork that would impress consumers with responsive on-device performance, integration with Microsoft’s mobile ecosystem, and compatibility with the more than 1 million apps available through the Google Play and other app stores.