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Diffstat (limited to 'eigen/blas/ssbmv.f')
| -rw-r--r-- | eigen/blas/ssbmv.f | 306 |
1 files changed, 306 insertions, 0 deletions
diff --git a/eigen/blas/ssbmv.f b/eigen/blas/ssbmv.f new file mode 100644 index 0000000..16893a2 --- /dev/null +++ b/eigen/blas/ssbmv.f @@ -0,0 +1,306 @@ + SUBROUTINE SSBMV(UPLO,N,K,ALPHA,A,LDA,X,INCX,BETA,Y,INCY) +* .. Scalar Arguments .. + REAL ALPHA,BETA + INTEGER INCX,INCY,K,LDA,N + CHARACTER UPLO +* .. +* .. Array Arguments .. + REAL A(LDA,*),X(*),Y(*) +* .. +* +* Purpose +* ======= +* +* SSBMV performs the matrix-vector operation +* +* y := alpha*A*x + beta*y, +* +* where alpha and beta are scalars, x and y are n element vectors and +* A is an n by n symmetric band matrix, with k super-diagonals. +* +* Arguments +* ========== +* +* UPLO - CHARACTER*1. +* On entry, UPLO specifies whether the upper or lower +* triangular part of the band matrix A is being supplied as +* follows: +* +* UPLO = 'U' or 'u' The upper triangular part of A is +* being supplied. +* +* UPLO = 'L' or 'l' The lower triangular part of A is +* being supplied. +* +* Unchanged on exit. +* +* N - INTEGER. +* On entry, N specifies the order of the matrix A. +* N must be at least zero. +* Unchanged on exit. +* +* K - INTEGER. +* On entry, K specifies the number of super-diagonals of the +* matrix A. K must satisfy 0 .le. K. +* Unchanged on exit. +* +* ALPHA - REAL . +* On entry, ALPHA specifies the scalar alpha. +* Unchanged on exit. +* +* A - REAL array of DIMENSION ( LDA, n ). +* Before entry with UPLO = 'U' or 'u', the leading ( k + 1 ) +* by n part of the array A must contain the upper triangular +* band part of the symmetric matrix, supplied column by +* column, with the leading diagonal of the matrix in row +* ( k + 1 ) of the array, the first super-diagonal starting at +* position 2 in row k, and so on. The top left k by k triangle +* of the array A is not referenced. +* The following program segment will transfer the upper +* triangular part of a symmetric band matrix from conventional +* full matrix storage to band storage: +* +* DO 20, J = 1, N +* M = K + 1 - J +* DO 10, I = MAX( 1, J - K ), J +* A( M + I, J ) = matrix( I, J ) +* 10 CONTINUE +* 20 CONTINUE +* +* Before entry with UPLO = 'L' or 'l', the leading ( k + 1 ) +* by n part of the array A must contain the lower triangular +* band part of the symmetric matrix, supplied column by +* column, with the leading diagonal of the matrix in row 1 of +* the array, the first sub-diagonal starting at position 1 in +* row 2, and so on. The bottom right k by k triangle of the +* array A is not referenced. +* The following program segment will transfer the lower +* triangular part of a symmetric band matrix from conventional +* full matrix storage to band storage: +* +* DO 20, J = 1, N +* M = 1 - J +* DO 10, I = J, MIN( N, J + K ) +* A( M + 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 +* ( k + 1 ). +* Unchanged on exit. +* +* X - REAL array of DIMENSION at least +* ( 1 + ( n - 1 )*abs( INCX ) ). +* 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. +* Unchanged on exit. +* +* Y - REAL array of DIMENSION at least +* ( 1 + ( n - 1 )*abs( INCY ) ). +* 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. +* +* Further Details +* =============== +* +* 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 TEMP1,TEMP2 + INTEGER I,INFO,IX,IY,J,JX,JY,KPLUS1,KX,KY,L +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL XERBLA +* .. +* .. Intrinsic Functions .. + INTRINSIC MAX,MIN +* .. +* +* Test the input parameters. +* + INFO = 0 + IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN + INFO = 1 + ELSE IF (N.LT.0) THEN + INFO = 2 + ELSE IF (K.LT.0) THEN + INFO = 3 + ELSE IF (LDA.LT. (K+1)) THEN + INFO = 6 + ELSE IF (INCX.EQ.0) THEN + INFO = 8 + ELSE IF (INCY.EQ.0) THEN + INFO = 11 + END IF + IF (INFO.NE.0) THEN + CALL XERBLA('SSBMV ',INFO) + RETURN + END IF +* +* Quick return if possible. +* + IF ((N.EQ.0) .OR. ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN +* +* Set up the start points in X and Y. +* + IF (INCX.GT.0) THEN + KX = 1 + ELSE + KX = 1 - (N-1)*INCX + END IF + IF (INCY.GT.0) THEN + KY = 1 + ELSE + KY = 1 - (N-1)*INCY + END IF +* +* Start the operations. In this version the elements of the array A +* are accessed sequentially with one pass through 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,N + Y(I) = ZERO + 10 CONTINUE + ELSE + DO 20 I = 1,N + Y(I) = BETA*Y(I) + 20 CONTINUE + END IF + ELSE + IY = KY + IF (BETA.EQ.ZERO) THEN + DO 30 I = 1,N + Y(IY) = ZERO + IY = IY + INCY + 30 CONTINUE + ELSE + DO 40 I = 1,N + Y(IY) = BETA*Y(IY) + IY = IY + INCY + 40 CONTINUE + END IF + END IF + END IF + IF (ALPHA.EQ.ZERO) RETURN + IF (LSAME(UPLO,'U')) THEN +* +* Form y when upper triangle of A is stored. +* + KPLUS1 = K + 1 + IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN + DO 60 J = 1,N + TEMP1 = ALPHA*X(J) + TEMP2 = ZERO + L = KPLUS1 - J + DO 50 I = MAX(1,J-K),J - 1 + Y(I) = Y(I) + TEMP1*A(L+I,J) + TEMP2 = TEMP2 + A(L+I,J)*X(I) + 50 CONTINUE + Y(J) = Y(J) + TEMP1*A(KPLUS1,J) + ALPHA*TEMP2 + 60 CONTINUE + ELSE + JX = KX + JY = KY + DO 80 J = 1,N + TEMP1 = ALPHA*X(JX) + TEMP2 = ZERO + IX = KX + IY = KY + L = KPLUS1 - J + DO 70 I = MAX(1,J-K),J - 1 + Y(IY) = Y(IY) + TEMP1*A(L+I,J) + TEMP2 = TEMP2 + A(L+I,J)*X(IX) + IX = IX + INCX + IY = IY + INCY + 70 CONTINUE + Y(JY) = Y(JY) + TEMP1*A(KPLUS1,J) + ALPHA*TEMP2 + JX = JX + INCX + JY = JY + INCY + IF (J.GT.K) THEN + KX = KX + INCX + KY = KY + INCY + END IF + 80 CONTINUE + END IF + ELSE +* +* Form y when lower triangle of A is stored. +* + IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN + DO 100 J = 1,N + TEMP1 = ALPHA*X(J) + TEMP2 = ZERO + Y(J) = Y(J) + TEMP1*A(1,J) + L = 1 - J + DO 90 I = J + 1,MIN(N,J+K) + Y(I) = Y(I) + TEMP1*A(L+I,J) + TEMP2 = TEMP2 + A(L+I,J)*X(I) + 90 CONTINUE + Y(J) = Y(J) + ALPHA*TEMP2 + 100 CONTINUE + ELSE + JX = KX + JY = KY + DO 120 J = 1,N + TEMP1 = ALPHA*X(JX) + TEMP2 = ZERO + Y(JY) = Y(JY) + TEMP1*A(1,J) + L = 1 - J + IX = JX + IY = JY + DO 110 I = J + 1,MIN(N,J+K) + IX = IX + INCX + IY = IY + INCY + Y(IY) = Y(IY) + TEMP1*A(L+I,J) + TEMP2 = TEMP2 + A(L+I,J)*X(IX) + 110 CONTINUE + Y(JY) = Y(JY) + ALPHA*TEMP2 + JX = JX + INCX + JY = JY + INCY + 120 CONTINUE + END IF + END IF +* + RETURN +* +* End of SSBMV . +* + END |