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Re: how much computers can do in one second

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RS Wood <rsw@therandymon.com>:

> Interesting website: they provide sample code and you have to guess how
> many iterations a computer can complete in a second.  Example:
>
> #include <stdlib.h>
>
> // Number to guess: How many iterations of
> // this loop can we go through in a second?
>
> int main(int argc, char **argv) {
>     int NUMBER, i, s;
>     NUMBER = atoi(argv[1]);
>
>     for (s = i = 0; i < NUMBER; ++i) {
>         s += 1;
>     }
>
>     return 0;
> }

Somewhat related. Here's a similar program to measure how fast the CPU's
32-bit integers wrap around:


========================================================================
#include <stdlib.h>

int main(int argc, char **argv)
{
    int i;
    for (i = 0; i < i + 1; i++)
        ;
    return 0;
}
========================================================================

Without optimization:

    $ cc -o test test.c
    $ time ./test

    real   0m4.880s
    user   0m4.873s
    sys    0m0.001s

With optimization:

    $ cc -O3 -o test test.c
    $ time ./test
    [stuck forever...]

> The speed of light is about 300,000 km/s. That translates to roughly 1
> ns per foot (yeah, I mix up my units... I'm Canadian...)
>
> THUS, a computer with a clock speed of 2 GHz will be able to execute,
> on a single core/thread, about 4 (four !) single-clock instructions
> between the moment photons leave your screen, and the moment they
> arrive into your eye 2 feet (roughly) later.
>
> _That_ should give you an idea of how fast modern computers really
> are.

It's even more impressive when you consider the speed of sound: 340 m/s
(or 256,000 miles per fortnight for you Canadians).

Your computer will be able to execute over 4 million (!) single-clock
instructions between the moment the beep leaves your speaker and the
moment it arrives into your ear 2 feet later.


BTW, is your 2-gigahertz processor executing two instructions per cycle?


Marko

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how much computers can do in one second RS Wood <rsw@therandymon.com> - 2017-03-27 14:43 +0300
  Re: how much computers can do in one second Marko Rauhamaa <marko@pacujo.net> - 2017-03-27 15:06 +0300
    Re: how much computers can do in one second Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-29 01:55 +0100
      Re: how much computers can do in one second Marko Rauhamaa <marko@pacujo.net> - 2017-03-29 10:25 +0300
      Re: how much computers can do in one second Richard Kettlewell <invalid@invalid.invalid> - 2017-03-29 08:52 +0100
        Re: how much computers can do in one second Marko Rauhamaa <marko@pacujo.net> - 2017-03-29 12:43 +0300
          Re: how much computers can do in one second Caecilius <nospam@spamless.invalid> - 2017-03-30 16:07 +0100
            Re: how much computers can do in one second Marko Rauhamaa <marko@pacujo.net> - 2017-03-30 19:09 +0300
              Re: how much computers can do in one second Bob Eager <news0006@eager.cx> - 2017-03-30 21:36 +0000
                Re: how much computers can do in one second Marko Rauhamaa <marko@pacujo.net> - 2017-03-31 09:56 +0300
  Re: how much computers can do in one second Huge <Huge@nowhere.much.invalid> - 2017-03-27 13:51 +0000
  Re: how much computers can do in one second Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 11:57 +1100
    Re: how much computers can do in one second Huge <Huge@nowhere.much.invalid> - 2017-03-28 09:51 +0000
      Re: how much computers can do in one second Bob Eager <news0006@eager.cx> - 2017-03-28 11:12 +0000

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