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How to detect NaN's in Fortran

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Old   July 25, 2002, 22:40
Default How to detect NaN's in Fortran
  #1
Wen Long
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Hi,friends

I would like to know how to detect NaN's in Fortran code. I want the code to stop at the first NaN when something gets weird and then step into.

Thanks,

Wen
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Old   July 26, 2002, 03:44
Default Re: How to detect NaN's in Fortran
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andy
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Look up "exception handling" in the documentation for your compiler. The implementation will vary from compiler to compiler.
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Old   July 27, 2002, 09:05
Default Re: How to detect NaN's in Fortran
  #3
Li Yang
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Hi, if you are using F77, the following would be useful for debugging:

f77 -g -ftrap=common -O3 file.f -o file.e

dbx file.e

catch fpe

run

You will find out which value is zero !

Regards

Li
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Old   July 28, 2002, 23:38
Default Re: How to detect NaN's in Fortran
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peter.zhao
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If you use digital Visual Fortran, you can set the entry of floating point exception to 1 instead of 3 on project/setting/fortran/floating point.

Good luck!
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Old   July 30, 2002, 22:07
Default Re: How to detect NaN's in Fortran
  #5
x.zhang
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Hi, there:

I have 2 methods:

1. To use Function IsNaN(*)

* real

it gives you a logical type

2. Do it my own way

Check if (a + 1.0) .eq. a , only NaNs will give

you a .true. answer

Good luck!
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