From: Roman Perepelitsa <roman.perepelitsa@gmail.com>
To: Daniel Shahaf <d.s@daniel.shahaf.name>, Zsh Users <zsh-users@zsh.org>
Subject: Re: shuffle array
Date: Mon, 2 Dec 2019 15:29:17 +0100 [thread overview]
Message-ID: <CAN=4vMpt+hQw2zxUC1LH+3bPymBX_5qqexFw-vqkN6ye+dG1ZQ@mail.gmail.com> (raw)
In-Reply-To: <20191202141421.sj7nlhsdrpqxpr42@chaz.gmail.com>
Another alternative is to implement the standard inplace shuffle
algorithm from scratch:
local -i i
for ((i = 2; i <= $#l; ++i)); do
local j=$((RANDOM % i + 1))
# swap l[i] and l[j]
local tmp=$l[i]
l[i]=$l[j]
l[j]=$tmp
done
Due to RANDOM having a rather narrow range, this will introduce bias
on large arrays and won't work at all on arrays with more than 32k
elements. These issues can be mitigated by replacing RANDOM with
(RANDOM << 15 | RANDOM) or even with (RANDOM << 30 | RANDOM << 15 |
RANDOM).
Roman.
next prev parent reply other threads:[~2019-12-02 14:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-29 3:20 Emanuel Berg
2019-11-29 6:42 ` Marc Chantreux
2019-11-29 8:19 ` Emanuel Berg
2019-11-29 8:43 ` Marc Chantreux
2019-11-29 8:50 ` Emanuel Berg
2019-11-29 13:38 ` Clint Adams
[not found] ` <8636e7w0w9.fsf__36104.0529723809$1575015640$gmane$org@zoho.eu>
2019-12-01 20:07 ` Stephane Chazelas
2019-12-01 21:22 ` Emanuel Berg
2019-12-01 21:25 ` Emanuel Berg
2019-12-01 23:46 ` Daniel Shahaf
2019-12-02 4:10 ` Emanuel Berg
2019-12-01 23:38 ` Daniel Shahaf
[not found] ` <20191201233848.7selcpkvenlu65px__33142.5388505281$1575243619$gmane$org@tarpaulin.shahaf.local2>
2019-12-02 14:14 ` Stephane Chazelas
2019-12-02 14:29 ` Roman Perepelitsa [this message]
2019-11-29 8:44 ` Emanuel Berg
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