From: matt@... (matt neuburg)
Date: 2007-08-20T04:14:58+09:00
Subject: Re: Float addition problem / Processor bug?

Christian Luginbuehl <dinkel@pimprecords.com> wrote:

> Hi,
> 
> Check out this weird IRB output:
> 
> === START ===
> irb(main):001:0> a = 2.95 + 2.95 + 2.95
> => 8.85
> irb(main):002:0> puts 8.85 - a
> -1.77635683940025e-15
> => nil
> === END ===
> 
> I'm running "ruby 1.8.6 (2007-06-07 patchlevel 36) [i486-linux]" on 
> Xubuntu beta with this processor:
> 
> === START cat /proc/cpuinfo ===
> processor       : 0
> vendor_id       : GenuineIntel
> cpu family      : 15
> model           : 2
> model name      : Intel(R) Pentium(R) 4 CPU 2.26GHz
> stepping        : 4
> cpu MHz         : 2271.951
> cache size      : 512 KB
> fdiv_bug        : no
> hlt_bug         : no
> f00f_bug        : no
> coma_bug        : no
> fpu             : yes
> fpu_exception   : yes
> cpuid level     : 2
> wp              : yes
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm up
> bogomips        : 4547.85
> clflush size    : 64
> === END cat /proc/cpuinfo ===
> 
> Is it a processor bug, a simple rounding problem or a ruby error?

Good reading:

<http://docs.sun.com/source/806-3568/ncg_goldberg.html>

m.
-- 
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