Hello LAPACK committee,
The LAPACK function IEEECK should be modified to keep compilers from
optimizing away the line
NAN6 = NAN5*0.0
And replacing it by NAN6 = 0.0.
I?ve seen this happen using two different compilers at their default level
of optimization. However, using
NAN6 = NAN5*ZERO
as in the attached file keeps this from happening.
Please let me know what you think about this.
Regards,
-----------------------------------------------------------------------------------------
Kevin Wadleigh e-mail: kwadleigh@Domain.Removed
Math Algorithms Tel: 214-576-9614
Convey Computer Corporation
-----------------------------------------------------------------------------------------
INTEGER FUNCTION IEEECK( ISPEC, ZERO, ONE )
*
* -- LAPACK auxiliary routine (version 3.2) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2006
*
* .. Scalar Arguments ..
INTEGER ISPEC
REAL ONE, ZERO
* ..
*
* Purpose
* =======
*
* IEEECK is called from the ILAENV to verify that Infinity and
* possibly NaN arithmetic is safe (i.e. will not trap).
*
* Arguments
* =========
*
* ISPEC (input) INTEGER
* Specifies whether to test just for inifinity arithmetic
* or whether to test for infinity and NaN arithmetic.
* = 0: Verify infinity arithmetic only.
* = 1: Verify infinity and NaN arithmetic.
*
* ZERO (input) REAL
* Must contain the value 0.0
* This is passed to prevent the compiler from optimizing
* away this code.
*
* ONE (input) REAL
* Must contain the value 1.0
* This is passed to prevent the compiler from optimizing
* away this code.
*
* RETURN VALUE: INTEGER
* = 0: Arithmetic failed to produce the correct answers
* = 1: Arithmetic produced the correct answers
*
* .. Local Scalars ..
REAL NAN1, NAN2, NAN3, NAN4, NAN5, NAN6, NEGINF,
$ NEGZRO, NEWZRO, POSINF
* ..
* .. Executable Statements ..
IEEECK = 1
*
POSINF = ONE / ZERO
IF( POSINF.LE.ONE ) THEN
IEEECK = 0
RETURN
END IF
*
NEGINF = -ONE / ZERO
IF( NEGINF.GE.ZERO ) THEN
IEEECK = 0
RETURN
END IF
*
NEGZRO = ONE / ( NEGINF+ONE )
IF( NEGZRO.NE.ZERO ) THEN
IEEECK = 0
RETURN
END IF
*
NEGINF = ONE / NEGZRO
IF( NEGINF.GE.ZERO ) THEN
IEEECK = 0
RETURN
END IF
*
NEWZRO = NEGZRO + ZERO
IF( NEWZRO.NE.ZERO ) THEN
IEEECK = 0
RETURN
END IF
*
POSINF = ONE / NEWZRO
IF( POSINF.LE.ONE ) THEN
IEEECK = 0
RETURN
END IF
*
NEGINF = NEGINF*POSINF
IF( NEGINF.GE.ZERO ) THEN
IEEECK = 0
RETURN
END IF
*
POSINF = POSINF*POSINF
IF( POSINF.LE.ONE ) THEN
IEEECK = 0
RETURN
END IF
*
*
*
*
* Return if we were only asked to check infinity arithmetic
*
IF( ISPEC.EQ.0 )
$ RETURN
*
NAN1 = POSINF + NEGINF
*
NAN2 = POSINF / NEGINF
*
NAN3 = POSINF / POSINF
*
NAN4 = POSINF*ZERO
*
NAN5 = NEGINF*NEGZRO
*
* To keep compilers from over optimizing, multiply NAN5 by variable ZERO
* NAN6 = NAN5*0.0
NAN6 = NAN5*ZERO
*
IF( NAN1.EQ.NAN1 ) THEN
IEEECK = 0
RETURN
END IF
*
IF( NAN2.EQ.NAN2 ) THEN
IEEECK = 0
RETURN
END IF
*
IF( NAN3.EQ.NAN3 ) THEN
IEEECK = 0
RETURN
END IF
*
IF( NAN4.EQ.NAN4 ) THEN
IEEECK = 0
RETURN
END IF
*
IF( NAN5.EQ.NAN5 ) THEN
IEEECK = 0
RETURN
END IF
*
IF( NAN6.EQ.NAN6 ) THEN
IEEECK = 0
RETURN
END IF
*
RETURN
END
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