dpbcon.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 217 行 · 第 1/2 页

<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           <a name="DLACN2.93"></a><a href="dlacn2.f.html#DLACN2.1">DLACN2</a>, <a name="DLATBS.93"></a><a href="dlatbs.f.html#DLATBS.1">DLATBS</a>, <a name="DRSCL.93"></a><a href="drscl.f.html#DRSCL.1">DRSCL</a>, <a name="XERBLA.93"></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
<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.103"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> )
      IF( .NOT.UPPER .AND. .NOT.<a name="LSAME.104"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> ) ) THEN
         INFO = -1
      ELSE IF( N.LT.0 ) THEN
         INFO = -2
      ELSE IF( KD.LT.0 ) THEN
         INFO = -3
      ELSE IF( LDAB.LT.KD+1 ) THEN
         INFO = -5
      ELSE IF( ANORM.LT.ZERO ) THEN
         INFO = -6
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.116"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="DPBCON.116"></a><a href="dpbcon.f.html#DPBCON.1">DPBCON</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>      RCOND = ZERO
      IF( N.EQ.0 ) THEN
         RCOND = ONE
         RETURN
      ELSE IF( ANORM.EQ.ZERO ) THEN
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span>      SMLNUM = <a name="DLAMCH.130"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'Safe minimum'</span> )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Estimate the 1-norm of the inverse.
</span><span class="comment">*</span><span class="comment">
</span>      KASE = 0
      NORMIN = <span class="string">'N'</span>
   10 CONTINUE
      CALL <a name="DLACN2.137"></a><a href="dlacn2.f.html#DLACN2.1">DLACN2</a>( N, WORK( N+1 ), WORK, IWORK, AINVNM, KASE, ISAVE )
      IF( KASE.NE.0 ) THEN
         IF( UPPER ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Multiply by inv(U').
</span><span class="comment">*</span><span class="comment">
</span>            CALL <a name="DLATBS.143"></a><a href="dlatbs.f.html#DLATBS.1">DLATBS</a>( <span class="string">'Upper'</span>, <span class="string">'Transpose'</span>, <span class="string">'Non-unit'</span>, NORMIN, N,
     $                   KD, AB, LDAB, WORK, SCALEL, WORK( 2*N+1 ),
     $                   INFO )
            NORMIN = <span class="string">'Y'</span>
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Multiply by inv(U).
</span><span class="comment">*</span><span class="comment">
</span>            CALL <a name="DLATBS.150"></a><a href="dlatbs.f.html#DLATBS.1">DLATBS</a>( <span class="string">'Upper'</span>, <span class="string">'No transpose'</span>, <span class="string">'Non-unit'</span>, NORMIN, N,
     $                   KD, AB, LDAB, WORK, SCALEU, WORK( 2*N+1 ),
     $                   INFO )
         ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Multiply by inv(L).
</span><span class="comment">*</span><span class="comment">
</span>            CALL <a name="DLATBS.157"></a><a href="dlatbs.f.html#DLATBS.1">DLATBS</a>( <span class="string">'Lower'</span>, <span class="string">'No transpose'</span>, <span class="string">'Non-unit'</span>, NORMIN, N,
     $                   KD, AB, LDAB, WORK, SCALEL, WORK( 2*N+1 ),
     $                   INFO )
            NORMIN = <span class="string">'Y'</span>
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Multiply by inv(L').
</span><span class="comment">*</span><span class="comment">
</span>            CALL <a name="DLATBS.164"></a><a href="dlatbs.f.html#DLATBS.1">DLATBS</a>( <span class="string">'Lower'</span>, <span class="string">'Transpose'</span>, <span class="string">'Non-unit'</span>, NORMIN, N,
     $                   KD, AB, LDAB, WORK, SCALEU, WORK( 2*N+1 ),
     $                   INFO )
         END IF
<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>         SCALE = SCALEL*SCALEU
         IF( SCALE.NE.ONE ) THEN
            IX = IDAMAX( N, WORK, 1 )
            IF( SCALE.LT.ABS( WORK( IX ) )*SMLNUM .OR. SCALE.EQ.ZERO )
     $         GO TO 20
            CALL <a name="DRSCL.176"></a><a href="drscl.f.html#DRSCL.1">DRSCL</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 / AINVNM ) / ANORM
<span class="comment">*</span><span class="comment">
</span>   20 CONTINUE
<span class="comment">*</span><span class="comment">
</span>      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="DPBCON.190"></a><a href="dpbcon.f.html#DPBCON.1">DPBCON</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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