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    1: *> \brief \b IEEECK
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at
    6: *            http://www.netlib.org/lapack/explore-html/
    7: *
    8: *> \htmlonly
    9: *> Download IEEECK + dependencies
   10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/ieeeck.f">
   11: *> [TGZ]</a>
   12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/ieeeck.f">
   13: *> [ZIP]</a>
   14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/ieeeck.f">
   15: *> [TXT]</a>
   16: *> \endhtmlonly
   17: *
   18: *  Definition:
   19: *  ===========
   20: *
   21: *       INTEGER          FUNCTION IEEECK( ISPEC, ZERO, ONE )
   22: *
   23: *       .. Scalar Arguments ..
   24: *       INTEGER            ISPEC
   25: *       REAL               ONE, ZERO
   26: *       ..
   27: *
   28: *
   29: *> \par Purpose:
   30: *  =============
   31: *>
   32: *> \verbatim
   33: *>
   34: *> IEEECK is called from the ILAENV to verify that Infinity and
   35: *> possibly NaN arithmetic is safe (i.e. will not trap).
   36: *> \endverbatim
   37: *
   38: *  Arguments:
   39: *  ==========
   40: *
   41: *> \param[in] ISPEC
   42: *> \verbatim
   43: *>          ISPEC is INTEGER
   44: *>          Specifies whether to test just for infinity arithmetic
   45: *>          or whether to test for infinity and NaN arithmetic.
   46: *>          = 0: Verify infinity arithmetic only.
   47: *>          = 1: Verify infinity and NaN arithmetic.
   48: *> \endverbatim
   49: *>
   50: *> \param[in] ZERO
   51: *> \verbatim
   52: *>          ZERO is REAL
   53: *>          Must contain the value 0.0
   54: *>          This is passed to prevent the compiler from optimizing
   55: *>          away this code.
   56: *> \endverbatim
   57: *>
   58: *> \param[in] ONE
   59: *> \verbatim
   60: *>          ONE is REAL
   61: *>          Must contain the value 1.0
   62: *>          This is passed to prevent the compiler from optimizing
   63: *>          away this code.
   64: *>
   65: *>  RETURN VALUE:  INTEGER
   66: *>          = 0:  Arithmetic failed to produce the correct answers
   67: *>          = 1:  Arithmetic produced the correct answers
   68: *> \endverbatim
   69: *
   70: *  Authors:
   71: *  ========
   72: *
   73: *> \author Univ. of Tennessee
   74: *> \author Univ. of California Berkeley
   75: *> \author Univ. of Colorado Denver
   76: *> \author NAG Ltd.
   77: *
   78: *> \ingroup OTHERauxiliary
   79: *
   80: *  =====================================================================
   81:       INTEGER          FUNCTION IEEECK( ISPEC, ZERO, ONE )
   82: *
   83: *  -- LAPACK auxiliary routine --
   84: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
   85: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   86: *
   87: *     .. Scalar Arguments ..
   88:       INTEGER            ISPEC
   89:       REAL               ONE, ZERO
   90: *     ..
   91: *
   92: *  =====================================================================
   93: *
   94: *     .. Local Scalars ..
   95:       REAL               NAN1, NAN2, NAN3, NAN4, NAN5, NAN6, NEGINF,
   96:      $                   NEGZRO, NEWZRO, POSINF
   97: *     ..
   98: *     .. Executable Statements ..
   99:       IEEECK = 1
  100: *
  101:       POSINF = ONE / ZERO
  102:       IF( POSINF.LE.ONE ) THEN
  103:          IEEECK = 0
  104:          RETURN
  105:       END IF
  106: *
  107:       NEGINF = -ONE / ZERO
  108:       IF( NEGINF.GE.ZERO ) THEN
  109:          IEEECK = 0
  110:          RETURN
  111:       END IF
  112: *
  113:       NEGZRO = ONE / ( NEGINF+ONE )
  114:       IF( NEGZRO.NE.ZERO ) THEN
  115:          IEEECK = 0
  116:          RETURN
  117:       END IF
  118: *
  119:       NEGINF = ONE / NEGZRO
  120:       IF( NEGINF.GE.ZERO ) THEN
  121:          IEEECK = 0
  122:          RETURN
  123:       END IF
  124: *
  125:       NEWZRO = NEGZRO + ZERO
  126:       IF( NEWZRO.NE.ZERO ) THEN
  127:          IEEECK = 0
  128:          RETURN
  129:       END IF
  130: *
  131:       POSINF = ONE / NEWZRO
  132:       IF( POSINF.LE.ONE ) THEN
  133:          IEEECK = 0
  134:          RETURN
  135:       END IF
  136: *
  137:       NEGINF = NEGINF*POSINF
  138:       IF( NEGINF.GE.ZERO ) THEN
  139:          IEEECK = 0
  140:          RETURN
  141:       END IF
  142: *
  143:       POSINF = POSINF*POSINF
  144:       IF( POSINF.LE.ONE ) THEN
  145:          IEEECK = 0
  146:          RETURN
  147:       END IF
  148: *
  149: *
  150: *
  151: *
  152: *     Return if we were only asked to check infinity arithmetic
  153: *
  154:       IF( ISPEC.EQ.0 )
  155:      $   RETURN
  156: *
  157:       NAN1 = POSINF + NEGINF
  158: *
  159:       NAN2 = POSINF / NEGINF
  160: *
  161:       NAN3 = POSINF / POSINF
  162: *
  163:       NAN4 = POSINF*ZERO
  164: *
  165:       NAN5 = NEGINF*NEGZRO
  166: *
  167:       NAN6 = NAN5*ZERO
  168: *
  169:       IF( NAN1.EQ.NAN1 ) THEN
  170:          IEEECK = 0
  171:          RETURN
  172:       END IF
  173: *
  174:       IF( NAN2.EQ.NAN2 ) THEN
  175:          IEEECK = 0
  176:          RETURN
  177:       END IF
  178: *
  179:       IF( NAN3.EQ.NAN3 ) THEN
  180:          IEEECK = 0
  181:          RETURN
  182:       END IF
  183: *
  184:       IF( NAN4.EQ.NAN4 ) THEN
  185:          IEEECK = 0
  186:          RETURN
  187:       END IF
  188: *
  189:       IF( NAN5.EQ.NAN5 ) THEN
  190:          IEEECK = 0
  191:          RETURN
  192:       END IF
  193: *
  194:       IF( NAN6.EQ.NAN6 ) THEN
  195:          IEEECK = 0
  196:          RETURN
  197:       END IF
  198: *
  199:       RETURN
  200:       END