From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-5.0 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 5235D203E1 for ; Wed, 27 Jul 2016 13:32:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755904AbcG0NcV (ORCPT ); Wed, 27 Jul 2016 09:32:21 -0400 Received: from cloud.peff.net ([50.56.180.127]:49792 "HELO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755891AbcG0NcU (ORCPT ); Wed, 27 Jul 2016 09:32:20 -0400 Received: (qmail 21501 invoked by uid 102); 27 Jul 2016 13:32:19 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.84) with SMTP; Wed, 27 Jul 2016 09:32:19 -0400 Received: (qmail 16653 invoked by uid 107); 27 Jul 2016 13:32:44 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) by peff.net (qpsmtpd/0.84) with SMTP; Wed, 27 Jul 2016 09:32:44 -0400 Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Wed, 27 Jul 2016 09:32:14 -0400 Date: Wed, 27 Jul 2016 09:32:14 -0400 From: Jeff King To: Torsten =?utf-8?Q?B=C3=B6gershausen?= Cc: larsxschneider@gmail.com, git@vger.kernel.org, gitster@pobox.com, jnareb@gmail.com, mlbright@gmail.com, remi.galan-alfonso@ensimag.grenoble-inp.fr, pclouds@gmail.com, e@80x24.org, ramsay@ramsayjones.plus.com Subject: Re: [PATCH v2 4/5] convert: generate large test files only once Message-ID: <20160727133214.GA14928@sigill.intra.peff.net> References: <20160722154900.19477-1-larsxschneider@gmail.com> <20160727000605.49982-1-larsxschneider@gmail.com> <20160727000605.49982-5-larsxschneider@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Wed, Jul 27, 2016 at 04:35:32AM +0200, Torsten Bögershausen wrote: > > + mkdir -p generated-test-data && > > + for i in $(test_seq 1 $T0021_LARGE_FILE_SIZE) > > + do > > + # Generate 1MB of empty data and 100 bytes of random characters > > + printf "%1048576d" 1 > > + printf "$(LC_ALL=C tr -dc "A-Za-z0-9" >8)) count=1 2>/dev/null)" > I'm not sure how portable /dev/urandom is. > The other thing, that "really random" numbers are an overkill, and > it may be easier to use pre-defined numbers, Right, there are a few reasons not to use /dev/urandom: - it's not portable - if we have to generate a lot of numbers, it drains the system's entropy pool, which is an unfriendly thing to do (and may also be slow) - it makes our tests random! This sounds like a good thing, but it means that if some input happens to cause failure, you are unlikely to be able to reproduce it. Instead, use test-genrandom, which is an LCG that starts at a seed. So you get a large amount of random-ish quickly and portably, and you get the same data each time. -Peff