[Cfp-interest] Signaling NaNs and Fortran

Thu Mar 17 17:38:24 PDT 2011

IBM XLF version 13 running on AIX 5.3 prints:

 snan, 32-bit prints as:  NaNS
 qnan, 32-bit prints as:  NaNQ
 snan, 64-bit prints as:  NaNS
 qnan, 64-bit prints as:  NaNQ

I modified the program to include quad precision using the IBM PPC's
"double double":

       program ieee_test_nan

       use, intrinsic :: ieee_arithmetic
       implicit none
       real(4) :: ss, sq
       real(8) :: ds, dq
       real(16) :: qs, qq

       ss = ieee_value(ss,ieee_signaling_nan)
       sq = ieee_value(sq,ieee_quiet_nan)
       ds = ieee_value(ds,ieee_signaling_nan)
       dq = ieee_value(dq,ieee_quiet_nan)
       qs = ieee_value(qs,ieee_signaling_nan)
       qq = ieee_value(qq,ieee_quiet_nan)

       write (*,*) "snan, 32-bit prints as: ", ss
       write (*,*) "qnan, 32-bit prints as: ", sq
       write (*,*) "snan, 64-bit prints as: ", ds
       write (*,*) "qnan, 64-bit prints as: ", dq
       write (*,*) "snan, 128-bit prints as: ", qs
       write (*,*) "qnan, 128-bit prints as: ", qq

       end

That printed:

 snan, 32-bit prints as:  NaNS
 qnan, 32-bit prints as:  NaNQ
 snan, 64-bit prints as:  NaNS
 qnan, 64-bit prints as:  NaNQ
 snan, 128-bit prints as:  NaNS
 qnan, 128-bit prints as:  NaNQ

- Ian McIntosh          IBM Canada Lab         Compiler Back End Support
and Development

  From:       "Fred J. Tydeman" <tydeman at tybor.com>                                                                                        

  To:         "cfp-interest at ucbtest.org" <cfp-interest at ucbtest.org>                                                                        

  Date:       03/16/2011 07:02 AM                                                                                                          

  Subject:    [Cfp-interest]  Signaling NaNs and Fortran                                                                                   

  Sent by:    cfp-interest-bounces at oakapple.net                                                                                            

Fortran, for some time, has had "support" for signaling NaNs.
The following program is supposed to create single and double
kinds of signaling and quiet NaNs; and then print them.
For those people who have access to Fortran compilers, would
you please run this and report back the results.
This is to help determine how C should print signaling NaNs.

       program ieee_test_nan

       use, intrinsic :: ieee_arithmetic
       implicit none
       real(4) :: ss, sq
       real(8) :: ds, dq

       ss = ieee_value(ss,ieee_signaling_nan)
       sq = ieee_value(sq,ieee_quiet_nan)
       ds = ieee_value(ds,ieee_signaling_nan)
       dq = ieee_value(dq,ieee_quiet_nan)

       write (*,*) "snan, 32-bit prints as: ", ss
       write (*,*) "qnan, 32-bit prints as: ", sq
       write (*,*) "snan, 64-bit prints as: ", ds
       write (*,*) "qnan, 64-bit prints as: ", dq

       end

---
Fred J. Tydeman        Tydeman Consulting
tydeman at tybor.com      Testing, numerics, programming
+1 (775) 358-9748      Vice-chair of PL22.11 (ANSI "C")
Sample C99+FPCE tests: http://www.tybor.com
Savers sleep well, investors eat well, spenders work forever.

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