slattr.f

来自「famous linear algebra library (LAPACK) p」· F 代码 · 共 649 行 · 第 1/2 页

               CALL SROTG( RA, RB, C, S )
*
*              Multiply by [ c -s;  s  c] on the right.
*
               IF( N.GT.J+1 )
     $            CALL SROT( N-J-1, A( J+2, J+1 ), 1, A( J+2, J ), 1, C,
     $                       -S )
*
*              Multiply by [-c  s; -s -c] on the left.
*
               IF( J.GT.1 )
     $            CALL SROT( J-1, A( J, 1 ), LDA, A( J+1, 1 ), LDA, -C,
     $                       S )
*
*              Negate A(J+1,J).
*
               A( J+1, J ) = -A( J+1, J )
  130       CONTINUE
         END IF
*
*     IMAT > 10:  Pathological test cases.  These triangular matrices
*     are badly scaled or badly conditioned, so when used in solving a
*     triangular system they may cause overflow in the solution vector.
*
      ELSE IF( IMAT.EQ.11 ) THEN
*
*        Type 11:  Generate a triangular matrix with elements between
*        -1 and 1. Give the diagonal norm 2 to make it well-conditioned.
*        Make the right hand side large so that it requires scaling.
*
         IF( UPPER ) THEN
            DO 140 J = 1, N
               CALL SLARNV( 2, ISEED, J, A( 1, J ) )
               A( J, J ) = SIGN( TWO, A( J, J ) )
  140       CONTINUE
         ELSE
            DO 150 J = 1, N
               CALL SLARNV( 2, ISEED, N-J+1, A( J, J ) )
               A( J, J ) = SIGN( TWO, A( J, J ) )
  150       CONTINUE
         END IF
*
*        Set the right hand side so that the largest value is BIGNUM.
*
         CALL SLARNV( 2, ISEED, N, B )
         IY = ISAMAX( N, B, 1 )
         BNORM = ABS( B( IY ) )
         BSCAL = BIGNUM / MAX( ONE, BNORM )
         CALL SSCAL( N, BSCAL, B, 1 )
*
      ELSE IF( IMAT.EQ.12 ) THEN
*
*        Type 12:  Make the first diagonal element in the solve small to
*        cause immediate overflow when dividing by T(j,j).
*        In type 12, the offdiagonal elements are small (CNORM(j) < 1).
*
         CALL SLARNV( 2, ISEED, N, B )
         TSCAL = ONE / MAX( ONE, REAL( N-1 ) )
         IF( UPPER ) THEN
            DO 160 J = 1, N
               CALL SLARNV( 2, ISEED, J, A( 1, J ) )
               CALL SSCAL( J-1, TSCAL, A( 1, J ), 1 )
               A( J, J ) = SIGN( ONE, A( J, J ) )
  160       CONTINUE
            A( N, N ) = SMLNUM*A( N, N )
         ELSE
            DO 170 J = 1, N
               CALL SLARNV( 2, ISEED, N-J+1, A( J, J ) )
               IF( N.GT.J )
     $            CALL SSCAL( N-J, TSCAL, A( J+1, J ), 1 )
               A( J, J ) = SIGN( ONE, A( J, J ) )
  170       CONTINUE
            A( 1, 1 ) = SMLNUM*A( 1, 1 )
         END IF
*
      ELSE IF( IMAT.EQ.13 ) THEN
*
*        Type 13:  Make the first diagonal element in the solve small to
*        cause immediate overflow when dividing by T(j,j).
*        In type 13, the offdiagonal elements are O(1) (CNORM(j) > 1).
*
         CALL SLARNV( 2, ISEED, N, B )
         IF( UPPER ) THEN
            DO 180 J = 1, N
               CALL SLARNV( 2, ISEED, J, A( 1, J ) )
               A( J, J ) = SIGN( ONE, A( J, J ) )
  180       CONTINUE
            A( N, N ) = SMLNUM*A( N, N )
         ELSE
            DO 190 J = 1, N
               CALL SLARNV( 2, ISEED, N-J+1, A( J, J ) )
               A( J, J ) = SIGN( ONE, A( J, J ) )
  190       CONTINUE
            A( 1, 1 ) = SMLNUM*A( 1, 1 )
         END IF
*
      ELSE IF( IMAT.EQ.14 ) THEN
*
*        Type 14:  T is diagonal with small numbers on the diagonal to
*        make the growth factor underflow, but a small right hand side
*        chosen so that the solution does not overflow.
*
         IF( UPPER ) THEN
            JCOUNT = 1
            DO 210 J = N, 1, -1
               DO 200 I = 1, J - 1
                  A( I, J ) = ZERO
  200          CONTINUE
               IF( JCOUNT.LE.2 ) THEN
                  A( J, J ) = SMLNUM
               ELSE
                  A( J, J ) = ONE
               END IF
               JCOUNT = JCOUNT + 1
               IF( JCOUNT.GT.4 )
     $            JCOUNT = 1
  210       CONTINUE
         ELSE
            JCOUNT = 1
            DO 230 J = 1, N
               DO 220 I = J + 1, N
                  A( I, J ) = ZERO
  220          CONTINUE
               IF( JCOUNT.LE.2 ) THEN
                  A( J, J ) = SMLNUM
               ELSE
                  A( J, J ) = ONE
               END IF
               JCOUNT = JCOUNT + 1
               IF( JCOUNT.GT.4 )
     $            JCOUNT = 1
  230       CONTINUE
         END IF
*
*        Set the right hand side alternately zero and small.
*
         IF( UPPER ) THEN
            B( 1 ) = ZERO
            DO 240 I = N, 2, -2
               B( I ) = ZERO
               B( I-1 ) = SMLNUM
  240       CONTINUE
         ELSE
            B( N ) = ZERO
            DO 250 I = 1, N - 1, 2
               B( I ) = ZERO
               B( I+1 ) = SMLNUM
  250       CONTINUE
         END IF
*
      ELSE IF( IMAT.EQ.15 ) THEN
*
*        Type 15:  Make the diagonal elements small to cause gradual
*        overflow when dividing by T(j,j).  To control the amount of
*        scaling needed, the matrix is bidiagonal.
*
         TEXP = ONE / MAX( ONE, REAL( N-1 ) )
         TSCAL = SMLNUM**TEXP
         CALL SLARNV( 2, ISEED, N, B )
         IF( UPPER ) THEN
            DO 270 J = 1, N
               DO 260 I = 1, J - 2
                  A( I, J ) = 0.
  260          CONTINUE
               IF( J.GT.1 )
     $            A( J-1, J ) = -ONE
               A( J, J ) = TSCAL
  270       CONTINUE
            B( N ) = ONE
         ELSE
            DO 290 J = 1, N
               DO 280 I = J + 2, N
                  A( I, J ) = 0.
  280          CONTINUE
               IF( J.LT.N )
     $            A( J+1, J ) = -ONE
               A( J, J ) = TSCAL
  290       CONTINUE
            B( 1 ) = ONE
         END IF
*
      ELSE IF( IMAT.EQ.16 ) THEN
*
*        Type 16:  One zero diagonal element.
*
         IY = N / 2 + 1
         IF( UPPER ) THEN
            DO 300 J = 1, N
               CALL SLARNV( 2, ISEED, J, A( 1, J ) )
               IF( J.NE.IY ) THEN
                  A( J, J ) = SIGN( TWO, A( J, J ) )
               ELSE
                  A( J, J ) = ZERO
               END IF
  300       CONTINUE
         ELSE
            DO 310 J = 1, N
               CALL SLARNV( 2, ISEED, N-J+1, A( J, J ) )
               IF( J.NE.IY ) THEN
                  A( J, J ) = SIGN( TWO, A( J, J ) )
               ELSE
                  A( J, J ) = ZERO
               END IF
  310       CONTINUE
         END IF
         CALL SLARNV( 2, ISEED, N, B )
         CALL SSCAL( N, TWO, B, 1 )
*
      ELSE IF( IMAT.EQ.17 ) THEN
*
*        Type 17:  Make the offdiagonal elements large to cause overflow
*        when adding a column of T.  In the non-transposed case, the
*        matrix is constructed to cause overflow when adding a column in
*        every other step.
*
         TSCAL = UNFL / ULP
         TSCAL = ( ONE-ULP ) / TSCAL
         DO 330 J = 1, N
            DO 320 I = 1, N
               A( I, J ) = 0.
  320       CONTINUE
  330    CONTINUE
         TEXP = ONE
         IF( UPPER ) THEN
            DO 340 J = N, 2, -2
               A( 1, J ) = -TSCAL / REAL( N+1 )
               A( J, J ) = ONE
               B( J ) = TEXP*( ONE-ULP )
               A( 1, J-1 ) = -( TSCAL / REAL( N+1 ) ) / REAL( N+2 )
               A( J-1, J-1 ) = ONE
               B( J-1 ) = TEXP*REAL( N*N+N-1 )
               TEXP = TEXP*2.
  340       CONTINUE
            B( 1 ) = ( REAL( N+1 ) / REAL( N+2 ) )*TSCAL
         ELSE
            DO 350 J = 1, N - 1, 2
               A( N, J ) = -TSCAL / REAL( N+1 )
               A( J, J ) = ONE
               B( J ) = TEXP*( ONE-ULP )
               A( N, J+1 ) = -( TSCAL / REAL( N+1 ) ) / REAL( N+2 )
               A( J+1, J+1 ) = ONE
               B( J+1 ) = TEXP*REAL( N*N+N-1 )
               TEXP = TEXP*2.
  350       CONTINUE
            B( N ) = ( REAL( N+1 ) / REAL( N+2 ) )*TSCAL
         END IF
*
      ELSE IF( IMAT.EQ.18 ) THEN
*
*        Type 18:  Generate a unit triangular matrix with elements
*        between -1 and 1, and make the right hand side large so that it
*        requires scaling.
*
         IF( UPPER ) THEN
            DO 360 J = 1, N
               CALL SLARNV( 2, ISEED, J-1, A( 1, J ) )
               A( J, J ) = ZERO
  360       CONTINUE
         ELSE
            DO 370 J = 1, N
               IF( J.LT.N )
     $            CALL SLARNV( 2, ISEED, N-J, A( J+1, J ) )
               A( J, J ) = ZERO
  370       CONTINUE
         END IF
*
*        Set the right hand side so that the largest value is BIGNUM.
*
         CALL SLARNV( 2, ISEED, N, B )
         IY = ISAMAX( N, B, 1 )
         BNORM = ABS( B( IY ) )
         BSCAL = BIGNUM / MAX( ONE, BNORM )
         CALL SSCAL( N, BSCAL, B, 1 )
*
      ELSE IF( IMAT.EQ.19 ) THEN
*
*        Type 19:  Generate a triangular matrix with elements between
*        BIGNUM/(n-1) and BIGNUM so that at least one of the column
*        norms will exceed BIGNUM.
*        1/3/91:  SLATRS no longer can handle this case
*
         TLEFT = BIGNUM / MAX( ONE, REAL( N-1 ) )
         TSCAL = BIGNUM*( REAL( N-1 ) / MAX( ONE, REAL( N ) ) )
         IF( UPPER ) THEN
            DO 390 J = 1, N
               CALL SLARNV( 2, ISEED, J, A( 1, J ) )
               DO 380 I = 1, J
                  A( I, J ) = SIGN( TLEFT, A( I, J ) ) + TSCAL*A( I, J )
  380          CONTINUE
  390       CONTINUE
         ELSE
            DO 410 J = 1, N
               CALL SLARNV( 2, ISEED, N-J+1, A( J, J ) )
               DO 400 I = J, N
                  A( I, J ) = SIGN( TLEFT, A( I, J ) ) + TSCAL*A( I, J )
  400          CONTINUE
  410       CONTINUE
         END IF
         CALL SLARNV( 2, ISEED, N, B )
         CALL SSCAL( N, TWO, B, 1 )
      END IF
*
*     Flip the matrix if the transpose will be used.
*
      IF( .NOT.LSAME( TRANS, 'N' ) ) THEN
         IF( UPPER ) THEN
            DO 420 J = 1, N / 2
               CALL SSWAP( N-2*J+1, A( J, J ), LDA, A( J+1, N-J+1 ),
     $                     -1 )
  420       CONTINUE
         ELSE
            DO 430 J = 1, N / 2
               CALL SSWAP( N-2*J+1, A( J, J ), 1, A( N-J+1, J+1 ),
     $                     -LDA )
  430       CONTINUE
         END IF
      END IF
*
      RETURN
*
*     End of SLATTR
*
      END