cgbtrs.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 239 行 · 第 1/2 页

         INFO = -2
      ELSE IF( KL.LT.0 ) THEN
         INFO = -3
      ELSE IF( KU.LT.0 ) THEN
         INFO = -4
      ELSE IF( NRHS.LT.0 ) THEN
         INFO = -5
      ELSE IF( LDAB.LT.( 2*KL+KU+1 ) ) THEN
         INFO = -7
      ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
         INFO = -10
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.115"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="CGBTRS.115"></a><a href="cgbtrs.f.html#CGBTRS.1">CGBTRS</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 .OR. NRHS.EQ.0 )
     $   RETURN
<span class="comment">*</span><span class="comment">
</span>      KD = KU + KL + 1
      LNOTI = KL.GT.0
<span class="comment">*</span><span class="comment">
</span>      IF( NOTRAN ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Solve  A*X = B.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Solve L*X = B, overwriting B with X.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        L is represented as a product of permutations and unit lower
</span><span class="comment">*</span><span class="comment">        triangular matrices L = P(1) * L(1) * ... * P(n-1) * L(n-1),
</span><span class="comment">*</span><span class="comment">        where each transformation L(i) is a rank-one modification of
</span><span class="comment">*</span><span class="comment">        the identity matrix.
</span><span class="comment">*</span><span class="comment">
</span>         IF( LNOTI ) THEN
            DO 10 J = 1, N - 1
               LM = MIN( KL, N-J )
               L = IPIV( J )
               IF( L.NE.J )
     $            CALL CSWAP( NRHS, B( L, 1 ), LDB, B( J, 1 ), LDB )
               CALL CGERU( LM, NRHS, -ONE, AB( KD+1, J ), 1, B( J, 1 ),
     $                     LDB, B( J+1, 1 ), LDB )
   10       CONTINUE
         END IF
<span class="comment">*</span><span class="comment">
</span>         DO 20 I = 1, NRHS
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Solve U*X = B, overwriting B with X.
</span><span class="comment">*</span><span class="comment">
</span>            CALL CTBSV( <span class="string">'Upper'</span>, <span class="string">'No transpose'</span>, <span class="string">'Non-unit'</span>, N, KL+KU,
     $                  AB, LDAB, B( 1, I ), 1 )
   20    CONTINUE
<span class="comment">*</span><span class="comment">
</span>      ELSE IF( <a name="LSAME.157"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( TRANS, <span class="string">'T'</span> ) ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Solve A**T * X = B.
</span><span class="comment">*</span><span class="comment">
</span>         DO 30 I = 1, NRHS
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Solve U**T * X = B, overwriting B with X.
</span><span class="comment">*</span><span class="comment">
</span>            CALL CTBSV( <span class="string">'Upper'</span>, <span class="string">'Transpose'</span>, <span class="string">'Non-unit'</span>, N, KL+KU, AB,
     $                  LDAB, B( 1, I ), 1 )
   30    CONTINUE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Solve L**T * X = B, overwriting B with X.
</span><span class="comment">*</span><span class="comment">
</span>         IF( LNOTI ) THEN
            DO 40 J = N - 1, 1, -1
               LM = MIN( KL, N-J )
               CALL CGEMV( <span class="string">'Transpose'</span>, LM, NRHS, -ONE, B( J+1, 1 ),
     $                     LDB, AB( KD+1, J ), 1, ONE, B( J, 1 ), LDB )
               L = IPIV( J )
               IF( L.NE.J )
     $            CALL CSWAP( NRHS, B( L, 1 ), LDB, B( J, 1 ), LDB )
   40       CONTINUE
         END IF
<span class="comment">*</span><span class="comment">
</span>      ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Solve A**H * X = B.
</span><span class="comment">*</span><span class="comment">
</span>         DO 50 I = 1, NRHS
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Solve U**H * X = B, overwriting B with X.
</span><span class="comment">*</span><span class="comment">
</span>            CALL CTBSV( <span class="string">'Upper'</span>, <span class="string">'Conjugate transpose'</span>, <span class="string">'Non-unit'</span>, N,
     $                  KL+KU, AB, LDAB, B( 1, I ), 1 )
   50    CONTINUE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Solve L**H * X = B, overwriting B with X.
</span><span class="comment">*</span><span class="comment">
</span>         IF( LNOTI ) THEN
            DO 60 J = N - 1, 1, -1
               LM = MIN( KL, N-J )
               CALL <a name="CLACGV.199"></a><a href="clacgv.f.html#CLACGV.1">CLACGV</a>( NRHS, B( J, 1 ), LDB )
               CALL CGEMV( <span class="string">'Conjugate transpose'</span>, LM, NRHS, -ONE,
     $                     B( J+1, 1 ), LDB, AB( KD+1, J ), 1, ONE,
     $                     B( J, 1 ), LDB )
               CALL <a name="CLACGV.203"></a><a href="clacgv.f.html#CLACGV.1">CLACGV</a>( NRHS, B( J, 1 ), LDB )
               L = IPIV( J )
               IF( L.NE.J )
     $            CALL CSWAP( NRHS, B( L, 1 ), LDB, B( J, 1 ), LDB )
   60       CONTINUE
         END IF
      END IF
      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="CGBTRS.212"></a><a href="cgbtrs.f.html#CGBTRS.1">CGBTRS</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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