Bug in Float? (was: NaN Error)


#1

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


#2

$ 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


#3

On Apr 17, 11:41 am, “Tim P.” removed_email_address@domain.invalid 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


#4

Hi,

At Wed, 18 Apr 2007 03:41:22 +0900,
Tim P. 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.


#5

On Apr 17, 12:41 pm, “Tim P.” removed_email_address@domain.invalid wrote:

numbers below Float::MAX are valid floating point numbers.
Now, when I run the exact same script on a Solaris machine, some odd

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


#6

On 4/17/07, Nobuyoshi N. removed_email_address@domain.invalid wrote:

Thank you very much, Nobu.

TwP