stgsy2.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 981 行 · 第 1/5 页

</span><span class="comment">*</span><span class="comment">     .. Parameters ..
</span>      INTEGER            LDZ
      PARAMETER          ( LDZ = 8 )
      REAL               ZERO, ONE
      PARAMETER          ( ZERO = 0.0E+0, ONE = 1.0E+0 )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      LOGICAL            NOTRAN
      INTEGER            I, IE, IERR, II, IS, ISP1, J, JE, JJ, JS, JSP1,
     $                   K, MB, NB, P, Q, ZDIM
      REAL               ALPHA, SCALOC
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Arrays ..
</span>      INTEGER            IPIV( LDZ ), JPIV( LDZ )
      REAL               RHS( LDZ ), Z( LDZ, LDZ )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.196"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      EXTERNAL           <a name="LSAME.197"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           SAXPY, SCOPY, SGEMM, SGEMV, SGER, <a name="SGESC2.200"></a><a href="sgesc2.f.html#SGESC2.1">SGESC2</a>,
     $                   <a name="SGETC2.201"></a><a href="sgetc2.f.html#SGETC2.1">SGETC2</a>, SSCAL, <a name="SLASET.201"></a><a href="slaset.f.html#SLASET.1">SLASET</a>, <a name="SLATDF.201"></a><a href="slatdf.f.html#SLATDF.1">SLATDF</a>, <a name="XERBLA.201"></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          MAX
<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">     Decode and test input parameters
</span><span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IERR = 0
      NOTRAN = <a name="LSAME.212"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( TRANS, <span class="string">'N'</span> )
      IF( .NOT.NOTRAN .AND. .NOT.<a name="LSAME.213"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( TRANS, <span class="string">'T'</span> ) ) THEN
         INFO = -1
      ELSE IF( NOTRAN ) THEN
         IF( ( IJOB.LT.0 ) .OR. ( IJOB.GT.2 ) ) THEN
            INFO = -2
         END IF
      END IF
      IF( INFO.EQ.0 ) THEN
         IF( M.LE.0 ) THEN
            INFO = -3
         ELSE IF( N.LE.0 ) THEN
            INFO = -4
         ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
            INFO = -5
         ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
            INFO = -8
         ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
            INFO = -10
         ELSE IF( LDD.LT.MAX( 1, M ) ) THEN
            INFO = -12
         ELSE IF( LDE.LT.MAX( 1, N ) ) THEN
            INFO = -14
         ELSE IF( LDF.LT.MAX( 1, M ) ) THEN
            INFO = -16
         END IF
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.240"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="STGSY2.240"></a><a href="stgsy2.f.html#STGSY2.1">STGSY2</a>'</span>, -INFO )
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Determine block structure of A
</span><span class="comment">*</span><span class="comment">
</span>      PQ = 0
      P = 0
      I = 1
   10 CONTINUE
      IF( I.GT.M )
     $   GO TO 20
      P = P + 1
      IWORK( P ) = I
      IF( I.EQ.M )
     $   GO TO 20
      IF( A( I+1, I ).NE.ZERO ) THEN
         I = I + 2
      ELSE
         I = I + 1
      END IF
      GO TO 10
   20 CONTINUE
      IWORK( P+1 ) = M + 1
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Determine block structure of B
</span><span class="comment">*</span><span class="comment">
</span>      Q = P + 1
      J = 1
   30 CONTINUE
      IF( J.GT.N )
     $   GO TO 40
      Q = Q + 1
      IWORK( Q ) = J
      IF( J.EQ.N )
     $   GO TO 40
      IF( B( J+1, J ).NE.ZERO ) THEN
         J = J + 2
      ELSE
         J = J + 1
      END IF
      GO TO 30
   40 CONTINUE
      IWORK( Q+1 ) = N + 1
      PQ = P*( Q-P-1 )
<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 (I, J) - subsystem
</span><span class="comment">*</span><span class="comment">           A(I, I) * R(I, J) - L(I, J) * B(J, J) = C(I, J)
</span><span class="comment">*</span><span class="comment">           D(I, I) * R(I, J) - L(I, J) * E(J, J) = F(I, J)
</span><span class="comment">*</span><span class="comment">        for I = P, P - 1, ..., 1; J = 1, 2, ..., Q
</span><span class="comment">*</span><span class="comment">
</span>         SCALE = ONE
         SCALOC = ONE
         DO 120 J = P + 2, Q
            JS = IWORK( J )
            JSP1 = JS + 1
            JE = IWORK( J+1 ) - 1
            NB = JE - JS + 1
            DO 110 I = P, 1, -1
<span class="comment">*</span><span class="comment">
</span>               IS = IWORK( I )
               ISP1 = IS + 1
               IE = IWORK( I+1 ) - 1
               MB = IE - IS + 1
               ZDIM = MB*NB*2
<span class="comment">*</span><span class="comment">
</span>               IF( ( MB.EQ.1 ) .AND. ( NB.EQ.1 ) ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">                 Build a 2-by-2 system Z * x = RHS
</span><span class="comment">*</span><span class="comment">
</span>                  Z( 1, 1 ) = A( IS, IS )
                  Z( 2, 1 ) = D( IS, IS )
                  Z( 1, 2 ) = -B( JS, JS )
                  Z( 2, 2 ) = -E( JS, JS )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">                 Set up right hand side(s)
</span><span class="comment">*</span><span class="comment">
</span>                  RHS( 1 ) = C( IS, JS )
                  RHS( 2 ) = F( IS, JS )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">                 Solve Z * x = RHS
</span><span class="comment">*</span><span class="comment">
</span>                  CALL <a name="SGETC2.324"></a><a href="sgetc2.f.html#SGETC2.1">SGETC2</a>( ZDIM, Z, LDZ, IPIV, JPIV, IERR )
                  IF( IERR.GT.0 )
     $               INFO = IERR
<span class="comment">*</span><span class="comment">
</span>                  IF( IJOB.EQ.0 ) THEN
                     CALL <a name="SGESC2.329"></a><a href="sgesc2.f.html#SGESC2.1">SGESC2</a>( ZDIM, Z, LDZ, RHS, IPIV, JPIV,
     $                            SCALOC )
                     IF( SCALOC.NE.ONE ) THEN
                        DO 50 K = 1, N
                           CALL SSCAL( M, SCALOC, C( 1, K ), 1 )
                           CALL SSCAL( M, SCALOC, F( 1, K ), 1 )
   50                   CONTINUE
                        SCALE = SCALE*SCALOC
                     END IF
                  ELSE
                     CALL <a name="SLATDF.339"></a><a href="slatdf.f.html#SLATDF.1">SLATDF</a>( IJOB, ZDIM, Z, LDZ, RHS, RDSUM,
     $                            RDSCAL, IPIV, JPIV )
                  END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">                 Unpack solution vector(s)
</span><span class="comment">*</span><span class="comment">
</span>                  C( IS, JS ) = RHS( 1 )
                  F( IS, JS ) = RHS( 2 )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">                 Substitute R(I, J) and L(I, J) into remaining
</span><span class="comment">*</span><span class="comment">                 equation.
</span><span class="comment">*</span><span class="comment">
</span>                  IF( I.GT.1 ) THEN
                     ALPHA = -RHS( 1 )
                     CALL SAXPY( IS-1, ALPHA, A( 1, IS ), 1, C( 1, JS ),
     $                           1 )
                     CALL SAXPY( IS-1, ALPHA, D( 1, IS ), 1, F( 1, JS ),
     $                           1 )
                  END IF
                  IF( J.LT.Q ) THEN
                     CALL SAXPY( N-JE, RHS( 2 ), B( JS, JE+1 ), LDB,
     $                           C( IS, JE+1 ), LDC )
                     CALL SAXPY( N-JE, RHS( 2 ), E( JS, JE+1 ), LDE,
     $                           F( IS, JE+1 ), LDF )
                  END IF
<span class="comment">*</span><span class="comment">
</span>               ELSE IF( ( MB.EQ.1 ) .AND. ( NB.EQ.2 ) ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">                 Build a 4-by-4 system Z * x = RHS
</span><span class="comment">*</span><span class="comment">
</span>                  Z( 1, 1 ) = A( IS, IS )
                  Z( 2, 1 ) = ZERO
                  Z( 3, 1 ) = D( IS, IS )
                  Z( 4, 1 ) = ZERO
<span class="comment">*</span><span class="comment">
</span>                  Z( 1, 2 ) = ZERO
                  Z( 2, 2 ) = A( IS, IS )