From: The Written Word Inc <bugs-ruby@...>
Date: 2011-10-29T15:26:41+09:00
Subject: [ruby-core:40503] [ruby-trunk - Bug #5497] Math.log10(10_000) error on HP-UX/PA


Issue #5497 has been updated by The Written Word Inc.


Yui NARUSE wrote:
> The Written Word Inc wrote:
> >   (ia64)
> >      p Math.log10(10_000)
> >      4
> 
> Show the result of `p 4.0`.

(ia64)
  p 4.0
  4.0
(pa-risc)
  p 4.0
  4.0

> >   (pa-risc)
> >      p Math.log10(10_000)
> >      3.9999999999999996
> 
> Build and run following C code:
> 
> % cat f.c
> #include <math.h>
> #include <stdio.h>
> 
> int main(void) {
>   printf("%a\n", log10(10000));
>   return 0;
> }
> %  gcc -lm f.c && ./a.out
> 0x1p+2 (or something)

$ cat t.c
#include <math.h>
#include <stdio.h>

int main(void) {
  printf("%f\n", log10(10000));
  printf("%a\n", log10(10000));
  return 0; 
}

(ia64)
  $ cc +O1 +Ofltacc +Olit=all +Oentrysched +Odataprefetch -lm t.c
  $ ./a.out
  4.000000
  0x1.0000000000000p+2

%a is only supported on HP-UX/IA systems, not HP-UX/PA. We're using the HP-UX C compiler to build Ruby as well.
----------------------------------------
Bug #5497: Math.log10(10_000) error on HP-UX/PA
http://redmine.ruby-lang.org/issues/5497

Author: The Written Word Inc
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 1.9.2
ruby -v: UNKNOWN


I've built 1.9.2 from svn revision at 33531 on HP-UX/PA and HP-UX/IA. I'm getting two different results for Math.log10(10_000) depending on IA64 and PA-RISC:
  (ia64)
     p Math.log10(10_000)
     4
  (pa-risc)
     p Math.log10(10_000)
     3.9999999999999996

Any idea where in the code I can look to try and fix this?


-- 
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