95 lines
3.5 KiB
Fortran
95 lines
3.5 KiB
Fortran
program nantest
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! This file: http://ftp.aset.psu.edu/pub/ger/fortran/hdk/nan.f90
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!
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!====NAN.F90 illustrates what works and what doesn't when
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! detecting a NaN. All but the Fortran 2003 IEEE_IS_NAN are not
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! Standard Fortran.
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!
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! Platforms: Windows 9x/Me/NT/2000, AIX 4.3, Linux
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! Compiler Notes:
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! Compaq Visual Fortran 6.6C with default
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! fpe settings (/fpe:3 /nocheck) and /OPTIMIZE:0
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! (ISNAN is an Elemental Intrinsic Function)
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! Options /fpe:0 /traceback will cause this
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! program to stop with error message,
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! James Giles points out that in order to actually print
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! minus zero from CVF, you have to compile with the
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! /assume:minus0 option.
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!
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! AIX XLF90 without optimization.
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! (ISNAN is part of a BOS Runtime C library;
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! thus ISNAN must be declared LOGICAL.)
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!
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! Linux Intel IFORT, use: -O0 (no optimization) and
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! -assume minus0
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!
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! g95 supports ieee_is_nan elemental function.
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!
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!
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! Author: hdkLESS at SPAM psu dot edu
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! Date: March, 2002, January 2005, August 2006.
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!
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! References:
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! http://www.psc.edu/general/software/packages/ieee/ieee.html
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! http://homepages.borland.com/efg2lab/Mathematics/NaN.htm
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! http://en.wikipedia.org/wiki/NaN
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!
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logical :: ISNAN
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integer :: i
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integer, Dimension (6) :: Iy
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real, Dimension (6) :: y
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integer :: IPInf, IMinf, IMZero
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real :: PInf, MInf, MZero, DivNan
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Character (Len=10), Dimension(6) :: NType
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data NType/'+Infinity','-Infinity','-0', 'NaN','NaN','0/0'/
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data IPInf/B'01111111100000000000000000000000'/ ! +Infinity
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data IMInf/B'11111111100000000000000000000000'/ ! -Infinity
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data IMZero/B'10000000000000000000000000000000'/ ! -0
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data Iy(1)/B'01111111100000000000000000000000'/ ! +Infinity
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data Iy(2)/B'11111111100000000000000000000000'/ ! -Infinity
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data Iy(3)/B'10000000000000000000000000000000'/ ! -0
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data Iy(4)/B'01111111100000100000000000000000'/ ! NaN
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data Iy(5)/B'11111111100100010001001010101010'/ ! NaN
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data Iy(6)/B'11111111110000000000000000000000'/ ! 0/0
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PInf = transfer(IPinf,Pinf)
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Minf = transfer(IMinf,Minf)
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MZero = transfer(IMZero,MZero)
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Y = transfer(IY,Y)
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! Some debug options for some compilers may flag the following
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! zero/zero as an exception. If so, comment out the next two lines.
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DivNan=0
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y(6)=DivNan/DivNan
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Do i=1,6
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print *, 'Test#',i,' ->',NType(i)
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if (y(i).eq.PInf) print *, 'Y = Plus Infinity'
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if (y(i).eq.MInf) print *, 'Y = Minus Infinity'
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if (y(i).eq.Mzero) print *, 'Y = Minus Zero'
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print *, 'y(Test#)=',y(i)
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print *, 'Testing each of three NaN detection methods:'
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! EQV -> true iff both A and B are True or iff both A and B are False.
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if( (y(i) > 0.0) .EQV. (y(i) <= 0.0)) then
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print *, '1) (y(Test#) > 0.0) .EQV. (y(Test#) <= 0.0)'
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end if
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if (y(i)/=y(i)) then
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print *, '2) (y(Test#)/=(y(Test#))'
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end if
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! If ISNAN is available for a specific compiler, uncomment the
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! following 3 lines.
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! if (ISNAN(y(i))) then
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! print *, '3) ISNAN(y(Test#))'
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! end if
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! if Fortran 2003 IEEE floating-point exception handling is available
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! uncomment the following 4 lines
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! use ieee_arithmetic
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! if (ieee_is_nan(y(i))) then
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! print *, '4) ieee_is_nan(y(Test#))'
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! end if
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print *, ' '
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End Do
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end program nantest
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