Issue 22730043: code review 22730043: math/rand: Float32/64 must only return values in [0,1)

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Issue 22730043: code review 22730043: math/rand: Float32/64 must only return values in [0,1) (Closed)

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Created:
10 years, 5 months ago by jeff.allen

Modified:
10 years, 4 months ago

Reviewers:
rsc

CC:
golang-dev, iant, rsc

Visibility:
Public.

Description

math/rand: Float32/64 must only return values in [0,1) Float32 and Float64 are now both created by taking the ratio of two integers which are chosen to fit entirely into the precision of the desired float type. The previous code could cast a Float64 with more than 23 bits of ".99999" into a Float32 of 1.0, which is not in [0,1). Float32 went from 15 to 21 ns/op (but is now correct). Fixes issue 6721.

Patch Set 1 #

Patch Set 2 : diff -r 0685a9549d5a https://code.google.com/p/go #

Patch Set 3 : diff -r 0685a9549d5a https://code.google.com/p/go #

Patch Set 4 : diff -r 0685a9549d5a https://code.google.com/p/go #

Created: 10 years, 5 months ago

Download [raw] [tar.bz2]

	Unified diffs	Side-by-side diffs	Delta from patch set	Stats (+22 lines, -4 lines)			Patch
M	src/pkg/math/rand/example_test.go	View	1	1 chunk	+2 lines, -2 lines	0 comments	Download
M	src/pkg/math/rand/rand.go	View	1	1 chunk	+2 lines, -2 lines	0 comments	Download
M	src/pkg/math/rand/rand_test.go	View	1 2 3	2 chunks	+18 lines, -0 lines	0 comments	Download

Messages

Total messages: 4

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jeff.allen

Hello golang-dev@googlegroups.com, I'd like you to review this change to https://code.google.com/p/go

10 years, 5 months ago (2013-11-07 08:53:59 UTC) #1

rsc

10 years, 4 months ago (2013-12-18 20:40:50 UTC) #4

*** Submitted as https://code.google.com/p/go/source/detail?r=3ed9d5c72102 ***

math/rand: Float32/64 must only return values in [0,1)

Float32 and Float64 are now both created by taking the ratio
of two integers which are chosen to fit entirely into the
precision of the desired float type. The previous code
could cast a Float64 with more than 23 bits of ".99999"
into a Float32 of 1.0, which is not in [0,1).

Float32 went from 15 to 21 ns/op (but is now correct).

Fixes issue 6721.

R=golang-dev, iant, rsc
CC=golang-dev
https://codereview.appspot.com/22730043

Committer: Russ Cox <rsc@golang.org>

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