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Diffstat (limited to 'blas/fortran/dspmv.f')
| -rw-r--r-- | blas/fortran/dspmv.f | 265 |
1 files changed, 265 insertions, 0 deletions
diff --git a/blas/fortran/dspmv.f b/blas/fortran/dspmv.f new file mode 100644 index 000000000..f6e121e76 --- /dev/null +++ b/blas/fortran/dspmv.f @@ -0,0 +1,265 @@ + SUBROUTINE DSPMV(UPLO,N,ALPHA,AP,X,INCX,BETA,Y,INCY) +* .. Scalar Arguments .. + DOUBLE PRECISION ALPHA,BETA + INTEGER INCX,INCY,N + CHARACTER UPLO +* .. +* .. Array Arguments .. + DOUBLE PRECISION AP(*),X(*),Y(*) +* .. +* +* Purpose +* ======= +* +* DSPMV 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 matrix, supplied in packed form. +* +* Arguments +* ========== +* +* UPLO - CHARACTER*1. +* On entry, UPLO specifies whether the upper or lower +* triangular part of the matrix A is supplied in the packed +* array AP as follows: +* +* UPLO = 'U' or 'u' The upper triangular part of A is +* supplied in AP. +* +* UPLO = 'L' or 'l' The lower triangular part of A is +* supplied in AP. +* +* Unchanged on exit. +* +* N - INTEGER. +* On entry, N specifies the order of the matrix A. +* N must be at least zero. +* Unchanged on exit. +* +* ALPHA - DOUBLE PRECISION. +* On entry, ALPHA specifies the scalar alpha. +* Unchanged on exit. +* +* AP - DOUBLE PRECISION array of DIMENSION at least +* ( ( n*( n + 1 ) )/2 ). +* Before entry with UPLO = 'U' or 'u', the array AP must +* contain the upper triangular part of the symmetric matrix +* packed sequentially, column by column, so that AP( 1 ) +* contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) +* and a( 2, 2 ) respectively, and so on. +* Before entry with UPLO = 'L' or 'l', the array AP must +* contain the lower triangular part of the symmetric matrix +* packed sequentially, column by column, so that AP( 1 ) +* contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 ) +* and a( 3, 1 ) respectively, and so on. +* Unchanged on exit. +* +* X - DOUBLE PRECISION array of dimension at least +* ( 1 + ( n - 1 )*abs( INCX ) ). +* Before entry, the incremented array X must contain the n +* element 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 - DOUBLE PRECISION. +* 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 - DOUBLE PRECISION array of dimension at least +* ( 1 + ( n - 1 )*abs( INCY ) ). +* Before entry, the incremented array Y must contain the n +* element 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 .. + DOUBLE PRECISION ONE,ZERO + PARAMETER (ONE=1.0D+0,ZERO=0.0D+0) +* .. +* .. Local Scalars .. + DOUBLE PRECISION TEMP1,TEMP2 + INTEGER I,INFO,IX,IY,J,JX,JY,K,KK,KX,KY +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL XERBLA +* .. +* +* 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 (INCX.EQ.0) THEN + INFO = 6 + ELSE IF (INCY.EQ.0) THEN + INFO = 9 + END IF + IF (INFO.NE.0) THEN + CALL XERBLA('DSPMV ',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 AP +* are accessed sequentially with one pass through AP. +* +* 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 + KK = 1 + IF (LSAME(UPLO,'U')) THEN +* +* Form y when AP contains the upper triangle. +* + IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN + DO 60 J = 1,N + TEMP1 = ALPHA*X(J) + TEMP2 = ZERO + K = KK + DO 50 I = 1,J - 1 + Y(I) = Y(I) + TEMP1*AP(K) + TEMP2 = TEMP2 + AP(K)*X(I) + K = K + 1 + 50 CONTINUE + Y(J) = Y(J) + TEMP1*AP(KK+J-1) + ALPHA*TEMP2 + KK = KK + J + 60 CONTINUE + ELSE + JX = KX + JY = KY + DO 80 J = 1,N + TEMP1 = ALPHA*X(JX) + TEMP2 = ZERO + IX = KX + IY = KY + DO 70 K = KK,KK + J - 2 + Y(IY) = Y(IY) + TEMP1*AP(K) + TEMP2 = TEMP2 + AP(K)*X(IX) + IX = IX + INCX + IY = IY + INCY + 70 CONTINUE + Y(JY) = Y(JY) + TEMP1*AP(KK+J-1) + ALPHA*TEMP2 + JX = JX + INCX + JY = JY + INCY + KK = KK + J + 80 CONTINUE + END IF + ELSE +* +* Form y when AP contains the lower triangle. +* + 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*AP(KK) + K = KK + 1 + DO 90 I = J + 1,N + Y(I) = Y(I) + TEMP1*AP(K) + TEMP2 = TEMP2 + AP(K)*X(I) + K = K + 1 + 90 CONTINUE + Y(J) = Y(J) + ALPHA*TEMP2 + KK = KK + (N-J+1) + 100 CONTINUE + ELSE + JX = KX + JY = KY + DO 120 J = 1,N + TEMP1 = ALPHA*X(JX) + TEMP2 = ZERO + Y(JY) = Y(JY) + TEMP1*AP(KK) + IX = JX + IY = JY + DO 110 K = KK + 1,KK + N - J + IX = IX + INCX + IY = IY + INCY + Y(IY) = Y(IY) + TEMP1*AP(K) + TEMP2 = TEMP2 + AP(K)*X(IX) + 110 CONTINUE + Y(JY) = Y(JY) + ALPHA*TEMP2 + JX = JX + INCX + JY = JY + INCY + KK = KK + (N-J+1) + 120 CONTINUE + END IF + END IF +* + RETURN +* +* End of DSPMV . +* + END |