Sources Esope | Cast3M

ieeeck
C IEEECK    SOURCE    BP208322  20/09/18    21:17:01     10718          
*> \brief \b IEEECK
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download IEEECK + dependencies
*> &lt;a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/ieeeck.f">
*> [TGZ]&lt;/a>
*> &lt;a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/ieeeck.f">
*> [ZIP]&lt;/a>
*> &lt;a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/ieeeck.f">
*> [TXT]&lt;/a>
*> \endhtmlonly
*
*  Definition:
*  ===========
*
*       INTEGER          FUNCTION IEEECK( ISPEC, ZERO, ONE )
*
*       .. Scalar Arguments ..
*       INTEGER            ISPEC
*       REAL               ONE, ZERO
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> IEEECK is called from the ILAENV to verify that Infinity and
*> possibly NaN arithmetic is safe (i.e. will not trap).
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] ISPEC
*> \verbatim
*>          ISPEC is 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.
*> \endverbatim
*>
*> \param[in] ZERO
*> \verbatim
*>          ZERO is REAL
*>          Must contain the value 0.0
*>          This is passed to prevent the compiler from optimizing
*>          away this code.
*> \endverbatim
*>
*> \param[in] ONE
*> \verbatim
*>          ONE is 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
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date December 2016
*
*> \ingroup OTHERauxiliary
*
*  =====================================================================
      INTEGER          FUNCTION IEEECK( ISPEC, ZERO, ONE )
*
*  -- LAPACK auxiliary routine (version 3.7.0) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     December 2016
 
      IMPLICIT INTEGER(I-N)
      IMPLICIT REAL*8(A-H,O-Z)
*
*     .. Scalar Arguments ..
      INTEGER            ISPEC
      REAL*8               ONE, ZERO
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      REAL*8               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
*
      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