strcon.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 222 行 · 第 1/2 页

      INTEGER            ISAMAX
      REAL               <a name="SLAMCH.94"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>, <a name="SLANTR.94"></a><a href="slantr.f.html#SLANTR.1">SLANTR</a>
      EXTERNAL           <a name="LSAME.95"></a><a href="lsame.f.html#LSAME.1">LSAME</a>, ISAMAX, <a name="SLAMCH.95"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>, <a name="SLANTR.95"></a><a href="slantr.f.html#SLANTR.1">SLANTR</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           <a name="SLACN2.98"></a><a href="slacn2.f.html#SLACN2.1">SLACN2</a>, <a name="SLATRS.98"></a><a href="slatrs.f.html#SLATRS.1">SLATRS</a>, <a name="SRSCL.98"></a><a href="srscl.f.html#SRSCL.1">SRSCL</a>, <a name="XERBLA.98"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC          ABS, MAX, REAL
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Executable Statements ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Test the input parameters.
</span><span class="comment">*</span><span class="comment">
</span>      INFO = 0
      UPPER = <a name="LSAME.108"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> )
      ONENRM = NORM.EQ.<span class="string">'1'</span> .OR. <a name="LSAME.109"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( NORM, <span class="string">'O'</span> )
      NOUNIT = <a name="LSAME.110"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( DIAG, <span class="string">'N'</span> )
<span class="comment">*</span><span class="comment">
</span>      IF( .NOT.ONENRM .AND. .NOT.<a name="LSAME.112"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( NORM, <span class="string">'I'</span> ) ) THEN
         INFO = -1
      ELSE IF( .NOT.UPPER .AND. .NOT.<a name="LSAME.114"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> ) ) THEN
         INFO = -2
      ELSE IF( .NOT.NOUNIT .AND. .NOT.<a name="LSAME.116"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( DIAG, <span class="string">'U'</span> ) ) THEN
         INFO = -3
      ELSE IF( N.LT.0 ) THEN
         INFO = -4
      ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
         INFO = -6
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.124"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="STRCON.124"></a><a href="strcon.f.html#STRCON.1">STRCON</a>'</span>, -INFO )
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Quick return if possible
</span><span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.0 ) THEN
         RCOND = ONE
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span>      RCOND = ZERO
      SMLNUM = <a name="SLAMCH.136"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>( <span class="string">'Safe minimum'</span> )*REAL( MAX( 1, N ) )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Compute the norm of the triangular matrix A.
</span><span class="comment">*</span><span class="comment">
</span>      ANORM = <a name="SLANTR.140"></a><a href="slantr.f.html#SLANTR.1">SLANTR</a>( NORM, UPLO, DIAG, N, N, A, LDA, WORK )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Continue only if ANORM &gt; 0.
</span><span class="comment">*</span><span class="comment">
</span>      IF( ANORM.GT.ZERO ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Estimate the norm of the inverse of A.
</span><span class="comment">*</span><span class="comment">
</span>         AINVNM = ZERO
         NORMIN = <span class="string">'N'</span>
         IF( ONENRM ) THEN
            KASE1 = 1
         ELSE
            KASE1 = 2
         END IF
         KASE = 0
   10    CONTINUE
         CALL <a name="SLACN2.157"></a><a href="slacn2.f.html#SLACN2.1">SLACN2</a>( N, WORK( N+1 ), WORK, IWORK, AINVNM, KASE, ISAVE )
         IF( KASE.NE.0 ) THEN
            IF( KASE.EQ.KASE1 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">              Multiply by inv(A).
</span><span class="comment">*</span><span class="comment">
</span>               CALL <a name="SLATRS.163"></a><a href="slatrs.f.html#SLATRS.1">SLATRS</a>( UPLO, <span class="string">'No transpose'</span>, DIAG, NORMIN, N, A,
     $                      LDA, WORK, SCALE, WORK( 2*N+1 ), INFO )
            ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">              Multiply by inv(A').
</span><span class="comment">*</span><span class="comment">
</span>               CALL <a name="SLATRS.169"></a><a href="slatrs.f.html#SLATRS.1">SLATRS</a>( UPLO, <span class="string">'Transpose'</span>, DIAG, NORMIN, N, A, LDA,
     $                      WORK, SCALE, WORK( 2*N+1 ), INFO )
            END IF
            NORMIN = <span class="string">'Y'</span>
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Multiply by 1/SCALE if doing so will not cause overflow.
</span><span class="comment">*</span><span class="comment">
</span>            IF( SCALE.NE.ONE ) THEN
               IX = ISAMAX( N, WORK, 1 )
               XNORM = ABS( WORK( IX ) )
               IF( SCALE.LT.XNORM*SMLNUM .OR. SCALE.EQ.ZERO )
     $            GO TO 20
               CALL <a name="SRSCL.181"></a><a href="srscl.f.html#SRSCL.1">SRSCL</a>( N, SCALE, WORK, 1 )
            END IF
            GO TO 10
         END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Compute the estimate of the reciprocal condition number.
</span><span class="comment">*</span><span class="comment">
</span>         IF( AINVNM.NE.ZERO )
     $      RCOND = ( ONE / ANORM ) / AINVNM
      END IF
<span class="comment">*</span><span class="comment">
</span>   20 CONTINUE
      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="STRCON.195"></a><a href="strcon.f.html#STRCON.1">STRCON</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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