From: mame@...
Date: 2016-03-14T13:30:00+00:00
Subject: [ruby-core:74297] [Ruby trunk Feature#12172] Array#max and Array#min
Issue #12172 has been reported by Yusuke Endoh.
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Feature #12172: Array#max and Array#min
https://bugs.ruby-lang.org/issues/12172
* Author: Yusuke Endoh
* Status: Open
* Priority: Normal
* Assignee:
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I propose to define `Array#max`. It is 10+ times faster than `Enumerable#max` since it skips a call to `#each`.
~~~~
a = [*1..10000]; 100000.times { a.max }
~~~~
* no patch: 22.424s
* Array#max defined: 1.740s
I don't think it is a good idea to copy all Enumerable methods to Array. But there are two reasons why `max` is special:
* It is one of the most basic operations for big data processing.
* We often use an idiom `[a, b].max` because of the lack of `Math.max(a, b)`.
I think the latter is particularly important. The idiom is concise but unsuitable in a hotspot since it creates a temporal array. If `Array#max` is defined, we can easily optimize the idiom by introducing a special instruction like `opt_newarray_max`.
~~~~
x, y = 1, 2; 10000000.times { [x, y].max }
~~~~
* no patch: 2.799s
* Array#max defined: 1.224s
* opt_newarray_max: 0.555s
~~~~
$ ./miniruby.opt2 --dump=insns -e 'x, y = 1, 2; [x. y].max'
== disasm: #<ISeq:<main>@-e>============================================
local table (size: 3, argc: 0 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 3] x [ 2] y
0000 trace 1 ( 1)
0002 putobject_OP_INT2FIX_O_1_C_
0003 putobject 2
0005 setlocal_OP__WC__0 2
0007 setlocal_OP__WC__0 3
0009 getlocal_OP__WC__0 3
0011 opt_send_without_block <callinfo!mid:y, argc:0, ARGS_SIMPLE>, <callcache>
0014 opt_newarray_max 1
0016 leave
~~~~
The patches are attached. (0001 is a preparation. 0002 introduces `Array#max`. 0003 introduces a special instruction.)
Of course, we can say the same for `Array#min`. The patches include `Array#min` too.
What do you think?
---Files--------------------------------
0001-refactor-a-data-structure-for-CMP_OPTIMIZABLE.patch (5.3 KB)
0002-introduce-Array-max-and-Array-min.patch (5.11 KB)
0003-introduce-opt_newarray_max-min-for-Array-max-min.patch (4.03 KB)
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