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Diffstat (limited to 'BLAS/SRC/sgbmv.f')
| -rw-r--r-- | BLAS/SRC/sgbmv.f | 297 |
1 files changed, 297 insertions, 0 deletions
diff --git a/BLAS/SRC/sgbmv.f b/BLAS/SRC/sgbmv.f new file mode 100644 index 00000000..6a79a039 --- /dev/null +++ b/BLAS/SRC/sgbmv.f @@ -0,0 +1,297 @@ + SUBROUTINE SGBMV(TRANS,M,N,KL,KU,ALPHA,A,LDA,X,INCX,BETA,Y,INCY) +* .. Scalar Arguments .. + REAL ALPHA,BETA + INTEGER INCX,INCY,KL,KU,LDA,M,N + CHARACTER TRANS +* .. +* .. Array Arguments .. + REAL A(LDA,*),X(*),Y(*) +* .. +* +* Purpose +* ======= +* +* SGBMV performs one of the matrix-vector operations +* +* y := alpha*A*x + beta*y, or y := alpha*A'*x + beta*y, +* +* where alpha and beta are scalars, x and y are vectors and A is an +* m by n band matrix, with kl sub-diagonals and ku super-diagonals. +* +* Arguments +* ========== +* +* TRANS - CHARACTER*1. +* On entry, TRANS specifies the operation to be performed as +* follows: +* +* TRANS = 'N' or 'n' y := alpha*A*x + beta*y. +* +* TRANS = 'T' or 't' y := alpha*A'*x + beta*y. +* +* TRANS = 'C' or 'c' y := alpha*A'*x + beta*y. +* +* Unchanged on exit. +* +* M - INTEGER. +* On entry, M specifies the number of rows of the matrix A. +* M must be at least zero. +* Unchanged on exit. +* +* N - INTEGER. +* On entry, N specifies the number of columns of the matrix A. +* N must be at least zero. +* Unchanged on exit. +* +* KL - INTEGER. +* On entry, KL specifies the number of sub-diagonals of the +* matrix A. KL must satisfy 0 .le. KL. +* Unchanged on exit. +* +* KU - INTEGER. +* On entry, KU specifies the number of super-diagonals of the +* matrix A. KU must satisfy 0 .le. KU. +* Unchanged on exit. +* +* ALPHA - REAL . +* On entry, ALPHA specifies the scalar alpha. +* Unchanged on exit. +* +* A - REAL array of DIMENSION ( LDA, n ). +* Before entry, the leading ( kl + ku + 1 ) by n part of the +* array A must contain the matrix of coefficients, supplied +* column by column, with the leading diagonal of the matrix in +* row ( ku + 1 ) of the array, the first super-diagonal +* starting at position 2 in row ku, the first sub-diagonal +* starting at position 1 in row ( ku + 2 ), and so on. +* Elements in the array A that do not correspond to elements +* in the band matrix (such as the top left ku by ku triangle) +* are not referenced. +* The following program segment will transfer a band matrix +* from conventional full matrix storage to band storage: +* +* DO 20, J = 1, N +* K = KU + 1 - J +* DO 10, I = MAX( 1, J - KU ), MIN( M, J + KL ) +* A( K + I, J ) = matrix( I, J ) +* 10 CONTINUE +* 20 CONTINUE +* +* Unchanged on exit. +* +* LDA - INTEGER. +* On entry, LDA specifies the first dimension of A as declared +* in the calling (sub) program. LDA must be at least +* ( kl + ku + 1 ). +* Unchanged on exit. +* +* X - REAL array of DIMENSION at least +* ( 1 + ( n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n' +* and at least +* ( 1 + ( m - 1 )*abs( INCX ) ) otherwise. +* Before entry, the incremented array X must contain the +* vector x. +* Unchanged on exit. +* +* INCX - INTEGER. +* On entry, INCX specifies the increment for the elements of +* X. INCX must not be zero. +* Unchanged on exit. +* +* BETA - REAL . +* On entry, BETA specifies the scalar beta. When BETA is +* supplied as zero then Y need not be set on input. +* Unchanged on exit. +* +* Y - REAL array of DIMENSION at least +* ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n' +* and at least +* ( 1 + ( n - 1 )*abs( INCY ) ) otherwise. +* Before entry, the incremented array Y must contain the +* vector y. On exit, Y is overwritten by the updated vector y. +* +* INCY - INTEGER. +* On entry, INCY specifies the increment for the elements of +* Y. INCY must not be zero. +* Unchanged on exit. +* +* +* Level 2 Blas routine. +* +* -- Written on 22-October-1986. +* Jack Dongarra, Argonne National Lab. +* Jeremy Du Croz, Nag Central Office. +* Sven Hammarling, Nag Central Office. +* Richard Hanson, Sandia National Labs. +* +* .. Parameters .. + REAL ONE,ZERO + PARAMETER (ONE=1.0E+0,ZERO=0.0E+0) +* .. +* .. Local Scalars .. + REAL TEMP + INTEGER I,INFO,IX,IY,J,JX,JY,K,KUP1,KX,KY,LENX,LENY +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL XERBLA +* .. +* .. Intrinsic Functions .. + INTRINSIC MAX,MIN +* .. +* +* Test the input parameters. +* + INFO = 0 + IF (.NOT.LSAME(TRANS,'N') .AND. .NOT.LSAME(TRANS,'T') .AND. + + .NOT.LSAME(TRANS,'C')) THEN + INFO = 1 + ELSE IF (M.LT.0) THEN + INFO = 2 + ELSE IF (N.LT.0) THEN + INFO = 3 + ELSE IF (KL.LT.0) THEN + INFO = 4 + ELSE IF (KU.LT.0) THEN + INFO = 5 + ELSE IF (LDA.LT. (KL+KU+1)) THEN + INFO = 8 + ELSE IF (INCX.EQ.0) THEN + INFO = 10 + ELSE IF (INCY.EQ.0) THEN + INFO = 13 + END IF + IF (INFO.NE.0) THEN + CALL XERBLA('SGBMV ',INFO) + RETURN + END IF +* +* Quick return if possible. +* + IF ((M.EQ.0) .OR. (N.EQ.0) .OR. + + ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN +* +* Set LENX and LENY, the lengths of the vectors x and y, and set +* up the start points in X and Y. +* + IF (LSAME(TRANS,'N')) THEN + LENX = N + LENY = M + ELSE + LENX = M + LENY = N + END IF + IF (INCX.GT.0) THEN + KX = 1 + ELSE + KX = 1 - (LENX-1)*INCX + END IF + IF (INCY.GT.0) THEN + KY = 1 + ELSE + KY = 1 - (LENY-1)*INCY + END IF +* +* Start the operations. In this version the elements of A are +* accessed sequentially with one pass through the band part of A. +* +* First form y := beta*y. +* + IF (BETA.NE.ONE) THEN + IF (INCY.EQ.1) THEN + IF (BETA.EQ.ZERO) THEN + DO 10 I = 1,LENY + Y(I) = ZERO + 10 CONTINUE + ELSE + DO 20 I = 1,LENY + Y(I) = BETA*Y(I) + 20 CONTINUE + END IF + ELSE + IY = KY + IF (BETA.EQ.ZERO) THEN + DO 30 I = 1,LENY + Y(IY) = ZERO + IY = IY + INCY + 30 CONTINUE + ELSE + DO 40 I = 1,LENY + Y(IY) = BETA*Y(IY) + IY = IY + INCY + 40 CONTINUE + END IF + END IF + END IF + IF (ALPHA.EQ.ZERO) RETURN + KUP1 = KU + 1 + IF (LSAME(TRANS,'N')) THEN +* +* Form y := alpha*A*x + y. +* + JX = KX + IF (INCY.EQ.1) THEN + DO 60 J = 1,N + IF (X(JX).NE.ZERO) THEN + TEMP = ALPHA*X(JX) + K = KUP1 - J + DO 50 I = MAX(1,J-KU),MIN(M,J+KL) + Y(I) = Y(I) + TEMP*A(K+I,J) + 50 CONTINUE + END IF + JX = JX + INCX + 60 CONTINUE + ELSE + DO 80 J = 1,N + IF (X(JX).NE.ZERO) THEN + TEMP = ALPHA*X(JX) + IY = KY + K = KUP1 - J + DO 70 I = MAX(1,J-KU),MIN(M,J+KL) + Y(IY) = Y(IY) + TEMP*A(K+I,J) + IY = IY + INCY + 70 CONTINUE + END IF + JX = JX + INCX + IF (J.GT.KU) KY = KY + INCY + 80 CONTINUE + END IF + ELSE +* +* Form y := alpha*A'*x + y. +* + JY = KY + IF (INCX.EQ.1) THEN + DO 100 J = 1,N + TEMP = ZERO + K = KUP1 - J + DO 90 I = MAX(1,J-KU),MIN(M,J+KL) + TEMP = TEMP + A(K+I,J)*X(I) + 90 CONTINUE + Y(JY) = Y(JY) + ALPHA*TEMP + JY = JY + INCY + 100 CONTINUE + ELSE + DO 120 J = 1,N + TEMP = ZERO + IX = KX + K = KUP1 - J + DO 110 I = MAX(1,J-KU),MIN(M,J+KL) + TEMP = TEMP + A(K+I,J)*X(IX) + IX = IX + INCX + 110 CONTINUE + Y(JY) = Y(JY) + ALPHA*TEMP + JY = JY + INCY + IF (J.GT.KU) KX = KX + INCX + 120 CONTINUE + END IF + END IF +* + RETURN +* +* End of SGBMV . +* + END |