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comp.lang.ruby

Bug in Float? (was: NaN Error

Tim Pease

4/17/2007 6:41:00 PM

I ran across some peculiar behavior yesterday when working with large
floating point values. Here is a small script that demonstrates the
behavior. My question is, is this the expected behavior or is this a
bug in Float?

> cat float_bug.rb
puts "ruby #{RUBY_VERSION} " +
"(#{RUBY_RELEASE_DATE} patchlevel #{RUBY_PATCHLEVEL}) " +
"[#{RUBY_PLATFORM}]"

puts "Float::MAX = #{Float::MAX}"
puts "1.0e+300 = #{1.0e+300}"
puts "1.0e+301 = #{1.0e+301}"
puts "1.0e+308 = #{1.0e+308}"
puts "1.0e+700 = #{1.0e+700}"

# EOF


When I run this script on my Windows machine, it produces the output I
would expect -- i.e. numbers above Float::MAX are "Infinity" and
numbers below Float::MAX are valid floating point numbers.

> ruby -w float_bug.rb
ruby 1.8.5 (2006-12-25 patchlevel 12) [i386-cygwin]
Float::MAX = 1.79769313486232e+308
1.0e+300 = 1.0e+300
1.0e+301 = 1.0e+301
1.0e+308 = 1.0e+308
1.0e+700 = Infinity


Now, when I run the exact same script on a Solaris machine, some odd
things start to happen

> ruby -w float_bug.rb
ruby 1.8.5 (2006-12-25 patchlevel 12) [sparc-solaris2.8]
Float::MAX = 1.79769313486232e+308
1.0e+300 = 1.0e+300
1.0e+301 = NaN
1.0e+308 = NaN
1.0e+700 = 8.55180271847103e+116


Whey are valid floats being treated as NaN? Better yet, why does
1.0e+700 get evaluated to 8.5518027e+116?


Once more on the Windows 1-click installed version of Ruby.

> ruby -w float_bug.rb
ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32]
Float::MAX = 1.79769313486232e+308
1.0e+300 = 1.0e+300
1.0e+301 = NaN
1.0e+308 = NaN
1.0e+700 = 1.0e+189


Any thoughts on this one? I encourage you to copy the float_bug.rb
script and try it out for yourself.

Blessings,
TwP
5 Answers

Dan Stevens (IAmAI)

4/17/2007 7:23:00 PM

0

$ ruby float_bug.rb
ruby 1.8.5 (2006-08-25) [i486-linux]
Float::MAX = 1.79769313486232e+308
1.0e+300 = 1.0e+300
1.0e+301 = 1.0e+301
1.0e+308 = 1.0e+308
1.0e+700 = 1.02189775487683e+36


On 17/04/07, Tim Pease <tim.pease@gmail.com> wrote:
> I ran across some peculiar behavior yesterday when working with large
> floating point values. Here is a small script that demonstrates the
> behavior. My question is, is this the expected behavior or is this a
> bug in Float?
>
> > cat float_bug.rb
> puts "ruby #{RUBY_VERSION} " +
> "(#{RUBY_RELEASE_DATE} patchlevel #{RUBY_PATCHLEVEL}) " +
> "[#{RUBY_PLATFORM}]"
>
> puts "Float::MAX = #{Float::MAX}"
> puts "1.0e+300 = #{1.0e+300}"
> puts "1.0e+301 = #{1.0e+301}"
> puts "1.0e+308 = #{1.0e+308}"
> puts "1.0e+700 = #{1.0e+700}"
>
> # EOF
>
>
> When I run this script on my Windows machine, it produces the output I
> would expect -- i.e. numbers above Float::MAX are "Infinity" and
> numbers below Float::MAX are valid floating point numbers.
>
> > ruby -w float_bug.rb
> ruby 1.8.5 (2006-12-25 patchlevel 12) [i386-cygwin]
> Float::MAX = 1.79769313486232e+308
> 1.0e+300 = 1.0e+300
> 1.0e+301 = 1.0e+301
> 1.0e+308 = 1.0e+308
> 1.0e+700 = Infinity
>
>
> Now, when I run the exact same script on a Solaris machine, some odd
> things start to happen
>
> > ruby -w float_bug.rb
> ruby 1.8.5 (2006-12-25 patchlevel 12) [sparc-solaris2.8]
> Float::MAX = 1.79769313486232e+308
> 1.0e+300 = 1.0e+300
> 1.0e+301 = NaN
> 1.0e+308 = NaN
> 1.0e+700 = 8.55180271847103e+116
>
>
> Whey are valid floats being treated as NaN? Better yet, why does
> 1.0e+700 get evaluated to 8.5518027e+116?
>
>
> Once more on the Windows 1-click installed version of Ruby.
>
> > ruby -w float_bug.rb
> ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32]
> Float::MAX = 1.79769313486232e+308
> 1.0e+300 = 1.0e+300
> 1.0e+301 = NaN
> 1.0e+308 = NaN
> 1.0e+700 = 1.0e+189
>
>
> Any thoughts on this one? I encourage you to copy the float_bug.rb
> script and try it out for yourself.
>
> Blessings,
> TwP
>
>

Gavin Kistner

4/17/2007 7:40:00 PM

0

On Apr 17, 11:41 am, "Tim Pease" <tim.pe...@gmail.com> wrote:
> Once more on the Windows 1-click installed version of Ruby.
>
> > ruby -w float_bug.rb
>
> ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32]
> Float::MAX = 1.79769313486232e+308
> 1.0e+300 = 1.0e+300
> 1.0e+301 = NaN
> 1.0e+308 = NaN
> 1.0e+700 = 1.0e+189

Further, (Windows, 1-click), same version:

C:\>ruby -v
ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32]

C:\>irb -v
irb 0.9.5(05/04/13)

C:\>irb
irb(main):001:0> 1.0e+800
=> 1.0e+289
irb(main):002:0> 1.0e+900
=> NaN
irb(main):003:0> 1.0e+1000
=> NaN
irb(main):004:0> 1.0e+1100
(irb):4: warning: Float 1.0e+1100 out of range
=> Infinity

Chris Shea

4/17/2007 9:18:00 PM

0

On Apr 17, 12:41 pm, "Tim Pease" <tim.pe...@gmail.com> wrote:
> I ran across some peculiar behavior yesterday when working with large
> floating point values. Here is a small script that demonstrates the
> behavior. My question is, is this the expected behavior or is this a
> bug in Float?
>
> > cat float_bug.rb
>
> puts "ruby #{RUBY_VERSION} " +
> "(#{RUBY_RELEASE_DATE} patchlevel #{RUBY_PATCHLEVEL}) " +
> "[#{RUBY_PLATFORM}]"
>
> puts "Float::MAX = #{Float::MAX}"
> puts "1.0e+300 = #{1.0e+300}"
> puts "1.0e+301 = #{1.0e+301}"
> puts "1.0e+308 = #{1.0e+308}"
> puts "1.0e+700 = #{1.0e+700}"
>
> # EOF
>
> When I run this script on my Windows machine, it produces the output I
> would expect -- i.e. numbers above Float::MAX are "Infinity" and
> numbers below Float::MAX are valid floating point numbers.
>
> > ruby -w float_bug.rb
>
> ruby 1.8.5 (2006-12-25 patchlevel 12) [i386-cygwin]
> Float::MAX = 1.79769313486232e+308
> 1.0e+300 = 1.0e+300
> 1.0e+301 = 1.0e+301
> 1.0e+308 = 1.0e+308
> 1.0e+700 = Infinity
>
> Now, when I run the exact same script on a Solaris machine, some odd
> things start to happen
>
> > ruby -w float_bug.rb
>
> ruby 1.8.5 (2006-12-25 patchlevel 12) [sparc-solaris2.8]
> Float::MAX = 1.79769313486232e+308
> 1.0e+300 = 1.0e+300
> 1.0e+301 = NaN
> 1.0e+308 = NaN
> 1.0e+700 = 8.55180271847103e+116
>
> Whey are valid floats being treated as NaN? Better yet, why does
> 1.0e+700 get evaluated to 8.5518027e+116?
>
> Once more on the Windows 1-click installed version of Ruby.
>
> > ruby -w float_bug.rb
>
> ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32]
> Float::MAX = 1.79769313486232e+308
> 1.0e+300 = 1.0e+300
> 1.0e+301 = NaN
> 1.0e+308 = NaN
> 1.0e+700 = 1.0e+189
>
> Any thoughts on this one? I encourage you to copy the float_bug.rb
> script and try it out for yourself.
>
> Blessings,
> TwP

On OS X 10.4.9

mvb:~ cms$ ruby float_bug.rb
ruby 1.8.6 (2007-03-13 patchlevel 0)
Float::MAX = 1.79769313486232e+308
1.0e+300 = 1.0e+300
1.0e+301 = NaN
1.0e+308 = NaN
1.0e+700 = 0.0

And my Xubuntu box (pre-RUBY_PATCHLEVEL apparently):

ruby 1.8.4 (2005-12-24)[i486-linux]
Float::MAX = 1.79769313486232e+308
1.0e+300 = 1.0e+300
1.0e+301 = 1.0e+301
1.0e+308 = 1.0e+308
1.0e+700 = 0.0

Nobuyoshi Nakada

4/18/2007 1:42:00 AM

0

Hi,

At Wed, 18 Apr 2007 03:41:22 +0900,
Tim Pease wrote in [ruby-talk:248272]:
> I ran across some peculiar behavior yesterday when working with large
> floating point values. Here is a small script that demonstrates the
> behavior. My question is, is this the expected behavior or is this a
> bug in Float?

Thank you, fixed now.

--
Nobu Nakada

Tim Pease

4/18/2007 2:57:00 PM

0

On 4/17/07, Nobuyoshi Nakada <nobu@ruby-lang.org> wrote:
> Hi,
>
> At Wed, 18 Apr 2007 03:41:22 +0900,
> Tim Pease wrote in [ruby-talk:248272]:
> > I ran across some peculiar behavior yesterday when working with large
> > floating point values. Here is a small script that demonstrates the
> > behavior. My question is, is this the expected behavior or is this a
> > bug in Float?
>
> Thank you, fixed now.
>

Thank you very much, Nobu.

TwP