X-Recipient: archive-cygwin AT delorie DOT com
X-SWARE-Spam-Status: No, hits=0.6 required=5.0	tests=AWL,BAYES_00,FREEMAIL_FROM,KAM_THEBAT,KHOP_THREADED,SPF_SOFTFAIL
X-Spam-Check-By: sourceware.org
Date: Wed, 27 Feb 2013 21:07:53 +0400
From: Andrey Repin <anrdaemon AT freemail DOT ru>
Reply-To: Andrey Repin <cygwin AT cygwin DOT com>
Message-ID: <1854370913.20130227210753@mtu-net.ru>
To: Adam Dinwoodie <Adam DOT Dinwoodie AT metaswitch DOT com>, cygwin AT cygwin DOT com
Subject: Re: Is there a source of moderately random data with good speed in Cygwin?
In-Reply-To: <CE9C056E12502146A72FD81290379E9A60928138@ENFIRHMBX1.datcon.co.uk>
References: <1212475491 DOT 20130227184011 AT mtu-net DOT ru> <CE9C056E12502146A72FD81290379E9A60928138 AT ENFIRHMBX1 DOT datcon DOT co DOT uk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-IsSubscribed: yes
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
Precedence: bulk
List-Id: <cygwin.cygwin.com>
List-Unsubscribe: <mailto:cygwin-unsubscribe-archive-cygwin=delorie DOT com AT cygwin DOT com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com

Greetings, Adam Dinwoodie!

>> 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.

I'm not very familiar with this kind of things in general, and as I'm writing
scripts for Cygwin right now, I though there may be some Cygwin specifics in
place.

> 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++)
>             putchar(c);
>     }

6Mb/sec, but thanks for a try.

> Alternatively, pre-cache some output and use that:

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

Seems, like that would be the most reasonable way of doing things.
And since this is, apparently, not specific to Cygwin, I consider the question
answered.


--
WBR,
Andrey Repin (anrdaemon AT freemail DOT ru) 27.02.2013, <20:42>

Sorry for my terrible english...


--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple