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BigDecimal losses precision in JRuby 1.7.19 #2650

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eljojo opened this issue Mar 5, 2015 · 3 comments
Closed

BigDecimal losses precision in JRuby 1.7.19 #2650

eljojo opened this issue Mar 5, 2015 · 3 comments
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@mkristian
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beginner JRuby 1.7.x stdlib
Milestone
JRuby 1.7.20

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@eljojo
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eljojo commented Mar 5, 2015

Hi,
I noticed there's a loss in precision when using 1.7.19. This is fixed in 9000.
I thought it'd be a good idea to report this anyways.

1.7.19:

$ ruby -v
jruby 1.7.19 (2.0.0p598) 2015-01-29 20786bd on Java HotSpot(TM) 64-Bit Server VM 1.8.0_25-b17 +jit [darwin-x86_64]
$ irb
>> require 'bigdecimal'
=> true
>> BigDecimal.new("10.9", 2).to_f
=> 11.0

9.0.0.0.pre1:

$ ruby -v
jruby 9.0.0.0.pre1 (2.2.0p0) 2015-01-20 d537cab Java HotSpot(TM) 64-Bit Server VM 25.25-b02 on 1.8.0_25-b17 +jit [darwin-x86_64]
$ irb
>> require 'bigdecimal'
=> true
>> BigDecimal.new("10.9", 2).to_f
=> 10.9

MRI 2.2.0:

$ ruby -v
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]
$ irb
>> require 'bigdecimal'
=> true
>> BigDecimal.new("10.9", 2).to_f
=> 10.9

I'm running this on mac using OS X 10.10.2 and the JVM:

$ java -version
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)
@headius
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headius commented Mar 12, 2015

Hmm...could be a difference in default rounding mode?

@headius
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headius commented Mar 12, 2015

Good beginner bug to sort out exactly why we differ here.

@eljojo
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eljojo commented Mar 12, 2015

I just tested and under 1.7.19, BigDecimal.new("10.4", 2).to_f => 10.0

@mkristian mkristian self-assigned this Mar 16, 2015
mkristian added a commit that referenced this issue Mar 20, 2015
@mkristian
fix the creation of BigDecimal from a String

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This commit is not signed, but one or more authors requires that any commit attributed to them is signed.
Learn about vigilant mode
5f4bb39 
follow what MRI is doing and ignore the precision

fixes #2650

Sponsored by Lookout Inc.
@enebo enebo added this to the JRuby 1.7.20 milestone Apr 28, 2015
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beginner JRuby 1.7.x stdlib
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JRuby 1.7.20
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@headius @enebo @rtyler @mkristian @eljojo