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Created a new project on the basis of an example on usage of procedure CLEARSTATUSFPQQ from Intel Fortran Compiler User and Reference Guides:
! Program to demonstrate CLEARSTATUSFPQQ.
! This program uses polling to detect that a
! floating-point exception has occurred.
! So, build this console application with the default
! floating-point exception behavior, fpe3.
! You need to specify compiler option /debug or /Od (Windows)
! or -O0 (Linux) to get the correct results
! PROGRAM CLEARFP
USE IFPORT
REAL*4 A,B,C
INTEGER*2 STS
A = 2.0E0
B = 0.0E0
! Poll and display initial floating point status
CALL GETSTATUSFPQQ(STS)
WRITE(*,'(1X,A,Z4.4)') 'Initial fp status = ',STS
! Cause a divide-by-zero exception
! Poll and display the new floating point status
C = A/B
CALL GETSTATUSFPQQ(STS)
WRITE(*,'(1X,A,Z4.4)') 'After div-by-zero fp status = ',STS
! If a divide by zero error occurred, clear the floating point
! status register so future exceptions can be detected.
IF ((STS .AND. FPSW$ZERODIVIDE) > 0) THEN
CALL CLEARSTATUSFPQQ()
CALL GETSTATUSFPQQ(STS)
WRITE(*,'(1X,A,Z4.4)') 'After CLEARSTATUSFPQQ fp status = ',STS
ENDIF
END
Installed compiler directive: /debug and /fpe:3
But as a result received on the screen following output:
Initial fp status = 0000
After div-by-zero fp status = 000
That is the program does not find out divide by zero?
In the Compaq Visual Fortran 6 program finds divide by zero!
Link Copied
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I have tried your program and I have the same behaviour, but only when compiled under IA32. If I compile in x64, the "fp status" prints 4 (divided by zero). There is something wrong here, but I don't know what it could be... I'm using Composer XE update 2. What compiler are you using?
Pedro
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I have Intel Visual Fortran 11.1.060 [IA-32].
Sergey
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A second possibility is a bug in the way the run-time library handles FP exceptions - use Intel Visual Fortran Composer XE 2011 to resolve that.
However, I'd suggest instead that you use the Fortran 2003 "IEEE Floating point" intrinsic modules to accomplish what you want. Here's an example:
[fortran] program zerodivide
use, intrinsic :: IEEE_EXCEPTIONS
use, intrinsic :: IEEE_ARITHMETIC
implicit none
real :: a, b, c
logical :: zerodivide_flag
! Disable halting on a zerodivide
call IEEE_SET_HALTING_MODE (IEEE_DIVIDE_BY_ZERO, .FALSE.)
a = 2.0
! In a loop, read B from the console and divide it into A
do
read (*,*,END=99) b
! Clear the exception flags
call IEEE_SET_FLAG (IEEE_USUAL, .FALSE.)
c = a / b
! Did we get an exception?
call IEEE_GET_FLAG (IEEE_DIVIDE_BY_ZERO, zerodivide_flag)
if (zerodivide_flag) then
write (*,*) "Divide by zero!"
else
write (*,*) "Result is ", c
end if
end do
99 continue
end program zerodivide
[/fortran]
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Thank you very much, Steve!!!
Sergey
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If to compile the program presented by you in configuration Win32 Release with Optimization directive: Speed the acceptable result turns out. If thus to change 29 line on
write (*, *) "Result is ok"
the result will be unacceptable. Why?
Sergey
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