Alessandro Di Martino

Sottile Impianti Website

noreply@blogger.com (Alessandro Di Martino) — Sun, 08 Jan 2012 20:15:00 +0000

During one or two weeks in July 2009 I have built a website for Sottile Impianti, a little electrical systems company.
I worked on all the graphic and commercial stuff, designing logos, business cards, sponsors... Here are some shots.

The website is no longer available. The image shows a page about photovoltaics and green energy.

XHTML 1.1 and CSS Valid.

Main Logo.

T-shirt Logo, an alternative version.

Side view of the vehicle graphics.

C, C++ Pointer Conversions

noreply@blogger.com (Alessandro Di Martino) — Wed, 03 Aug 2011 16:34:00 +0000

Pointers to one type may be converted to pointers to another type. A pointer to an object may be converted to a pointer to an object whose type requires less or equally strict storage alignment and back again without change.

In many situations, void pointers are preferred; pointers to type void are pointers that point to a value that has no type, this allows void pointers to point to any data type. However in C++ (unlike in C) conversions from pointers to any type to pointers to type void require an explicit conversion.

The code below got compiled on an Intel Core i7 with the MSVC Compiler:

#include <stdio.h>

int main()
{
    const double d = 371564759.278651;

    // Pointers of different type have the same size:
    // 8 bytes on a 64-bit platform.
    printf("\n%u", (unsigned int)sizeof(double*)); // 8
    printf("\n%u", (unsigned int)sizeof(char*));   // 8
    printf("\n%u", (unsigned int)sizeof(void*));   // 8

    // Pointer conversions do not affect result
    printf("\n%f", *(double*)(char*)&d);  // 371564759.278651
    printf("\n%f", *(double*)(void*)&d);  // 371564759.278651
    printf("\n%f", *(double*)(float*)&d); // 371564759.278651
    printf("\n%f", *(double*)(long*)&d);  // 371564759.278651

    return 0;
}

References:
[1] Brian W. Kernighan and Dennis M. Ritchie. The C Programming Language, Second Edition.

Amdahl’s Law

noreply@blogger.com (Alessandro Di Martino) — Thu, 28 Jul 2011 16:26:00 +0000

Amdahl's Law is a model used to quantify the maximum expected performance gain that can be obtained by improving only some parts of a system. The Law states that the overall improvement of a system is limited by the time the improved part is used. In other words, as you can see in the following example, it is better to improve the most frequent case than to make enhancements to rarely used parts of a program.

Consider a task consisting of two sequential parts where the purple one takes 70% of the time of the whole computation and the blue part the remaining 30%. By working hard, one may be able to make the blue part 3 times faster, but this only reduces the time for the whole computation by a 20%. In contrast, one may need to perform less work to make the purple part be twice as fast, obtaining a speedup of 35%.

References:
[1] Wikipedia.org. http://en.wikipedia.org/wiki/Amdahl's_law

PixRev

noreply@blogger.com (Alessandro Di Martino) — Mon, 18 Jul 2011 07:23:00 +0000

PixRev is one of my first projects, a simple image conversion software I wrote in Python just for fun. I released it for free in 2006 when I was 16 years old.

At that time my programming techniques were really primitive, so I don't consider PixRev a well designed software, but it does its work! And you can still find it on the net.

PixRev main window.

The logo of PixRev website (Python Lab).
It is displayed in the info window.

First Post, Testing the New Theme

noreply@blogger.com (Alessandro Di Martino) — Sat, 16 Jul 2011 07:20:00 +0000

Hello World! This is the first post, so I can test the website and the new theme I’ve written in HTML5 and CSS3, speaking of which, do you like it?!