ieeeck.f

Go to the documentation of this file.

*> \brief \b IEEECK
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download IEEECK + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/ieeeck.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/ieeeck.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/ieeeck.f">
*> [TXT]</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 infinity 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.
*
*> \ingroup ieeeck
*
*  =====================================================================
      INTEGER          FUNCTION ieeeck( ISPEC, ZERO, ONE )
*
*  -- LAPACK auxiliary routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      INTEGER            ispec
      REAL               one, zero
*     ..
*
*  =====================================================================
*
*     .. 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
*
      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