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From: Lars Schneider <larsxschneider@gmail.com>
To: Jeff King <peff@peff.net>
Cc: "Torsten Bögershausen" <tboegi@web.de>,
	"Git Mailing List" <git@vger.kernel.org>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Jakub Narębski" <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
Date: Wed, 27 Jul 2016 18:50:40 +0200	[thread overview]
Message-ID: <1D133FC4-032F-434A-882C-5931AA285CD9@gmail.com> (raw)
In-Reply-To: <20160727133214.GA14928@sigill.intra.peff.net>


> On 27 Jul 2016, at 15:32, Jeff King <peff@peff.net> wrote:
> 
> 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" </dev/urandom | dd bs=$((RANDOM>>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.

Thank you! That's exactly what I need here :-)

- Lars

  reply	other threads:[~2016-07-27 16:50 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-22 15:48 [PATCH v1 0/3] Git filter protocol larsxschneider
2016-07-22 15:48 ` [PATCH v1 1/3] convert: quote filter names in error messages larsxschneider
2016-07-22 15:48 ` [PATCH v1 2/3] convert: modernize tests larsxschneider
2016-07-26 15:18   ` Remi Galan Alfonso
2016-07-26 20:40     ` Junio C Hamano
2016-07-22 15:49 ` [PATCH v1 3/3] convert: add filter.<driver>.useProtocol option larsxschneider
2016-07-22 22:32   ` Torsten Bögershausen
2016-07-24 12:09     ` Lars Schneider
2016-07-22 23:19   ` Ramsay Jones
2016-07-22 23:28     ` Ramsay Jones
2016-07-24 17:16     ` Lars Schneider
2016-07-24 22:36       ` Ramsay Jones
2016-07-24 23:22         ` Jakub Narębski
2016-07-25 20:32           ` Lars Schneider
2016-07-26 10:58             ` Jakub Narębski
2016-07-25 20:24         ` Lars Schneider
2016-07-23  0:11   ` Jakub Narębski
2016-07-23  7:27     ` Eric Wong
2016-07-26 20:00       ` Jeff King
2016-07-24 18:36     ` Lars Schneider
2016-07-24 20:14       ` Jakub Narębski
2016-07-24 21:30         ` Jakub Narębski
2016-07-25 20:16           ` Lars Schneider
2016-07-26 12:24             ` Jakub Narębski
2016-07-25 20:09         ` Lars Schneider
2016-07-26 14:18           ` Jakub Narębski
2016-07-23  8:14   ` Eric Wong
2016-07-24 19:11     ` Lars Schneider
2016-07-25  7:27       ` Eric Wong
2016-07-25 15:48       ` Duy Nguyen
2016-07-22 21:39 ` [PATCH v1 0/3] Git filter protocol Junio C Hamano
2016-07-24 11:24   ` Lars Schneider
2016-07-26 20:11     ` Jeff King
2016-07-27  0:06 ` [PATCH v2 0/5] " larsxschneider
2016-07-27  0:06   ` [PATCH v2 1/5] convert: quote filter names in error messages larsxschneider
2016-07-27 20:01     ` Jakub Narębski
2016-07-28  8:23       ` Lars Schneider
2016-07-27  0:06   ` [PATCH v2 2/5] convert: modernize tests larsxschneider
2016-07-27  0:06   ` [PATCH v2 3/5] pkt-line: extract and use `set_packet_header` function larsxschneider
2016-07-27  0:20     ` Junio C Hamano
2016-07-27  9:13       ` Lars Schneider
2016-07-27 16:31         ` Junio C Hamano
2016-07-27  0:06   ` [PATCH v2 4/5] convert: generate large test files only once larsxschneider
2016-07-27  2:35     ` Torsten Bögershausen
2016-07-27 13:32       ` Jeff King
2016-07-27 16:50         ` Lars Schneider [this message]
2016-07-27  0:06   ` [PATCH v2 5/5] convert: add filter.<driver>.process option larsxschneider
2016-07-27  1:32     ` Jeff King
2016-07-27 17:31       ` Lars Schneider
2016-07-27 18:11         ` Jeff King
2016-07-28 12:10           ` Lars Schneider
2016-07-28 13:35             ` Jeff King
2016-07-27  9:41     ` Eric Wong
2016-07-29 10:38       ` Lars Schneider
2016-07-29 11:24         ` Jakub Narębski
2016-07-29 11:31           ` Lars Schneider
2016-08-05 18:55         ` Eric Wong
2016-08-05 23:26           ` Lars Schneider
2016-08-05 23:38             ` Eric Wong
2016-07-27 23:31     ` Jakub Narębski
2016-07-29  8:04       ` Lars Schneider
2016-07-29 17:35         ` Junio C Hamano
2016-07-29 23:11           ` Jakub Narębski
2016-07-29 23:44             ` Lars Schneider
2016-07-30  9:32               ` Jakub Narębski
2016-07-28 10:32     ` Torsten Bögershausen
2016-07-27 19:08   ` [PATCH v2 0/5] Git filter protocol Jakub Narębski
2016-07-28  7:16     ` Lars Schneider
2016-07-28 10:42       ` Jakub Narębski
2016-07-28 13:29       ` Jeff King
2016-07-29  7:40         ` Jakub Narębski
2016-07-29  8:14           ` Lars Schneider
2016-07-29 15:57             ` Jeff King
2016-07-29 16:20               ` Lars Schneider
2016-07-29 16:50                 ` Jeff King
2016-07-29 17:43                   ` Lars Schneider
2016-07-29 18:27                     ` Jeff King

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