Is there a source of moderately random data with good speed in Cygwin?

Adam Dinwoodie
Wed Feb 27 15:33:00 GMT 2013

Andrey Repin wrote:
> I was need to pipe some bytes through application and watch it's reaction.
> But with /dev/urandom the stream speed is only about 40Mb/sec.  Using
> /dev/zero, however, makes it 3 orders of magnitude faster (~35Gb/s), but for
> technical reasons, using monotonous sequence is highly undesirable.  Is there
> any more performant source of non-monotonous byte sequences available to
> Cygwin? I would be pretty happy even with sequential bytes, I think. Only two
> reservations are good performance (something around 100 Mb/sec or more would
> suffice) and a degree of randomness.

You want a source of data that's non-monotonous but faster than /dev/urandom.
I don't see how this is a Cygwin issue at all, and thus I don't think it
belongs on this list.

Nonetheless, I suspect the easiest solution is to write a short C program to
produce your output, along the lines of (untested):

    #include <stdio.h>
    int main () {
        unsigned char c;
        for (c = 0;; c++)

Alternatively, pre-cache some output and use that:

    head --bytes=1G >/var/cache/randomdata
    ./myapp <(while :;do cat /var/cache/randomdata; done)

Adam Dinwoodie

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