diff options
Diffstat (limited to 'blas/sspr.f')
| -rw-r--r-- | blas/sspr.f | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/blas/sspr.f b/blas/sspr.f new file mode 100644 index 000000000..bae92612e --- /dev/null +++ b/blas/sspr.f @@ -0,0 +1,202 @@ + SUBROUTINE SSPR(UPLO,N,ALPHA,X,INCX,AP) +* .. Scalar Arguments .. + REAL ALPHA + INTEGER INCX,N + CHARACTER UPLO +* .. +* .. Array Arguments .. + REAL AP(*),X(*) +* .. +* +* Purpose +* ======= +* +* SSPR performs the symmetric rank 1 operation +* +* A := alpha*x*x' + A, +* +* where alpha is a real scalar, x is an n element vector 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 - REAL . +* On entry, ALPHA specifies the scalar alpha. +* Unchanged on exit. +* +* X - REAL 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. +* +* AP - REAL 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. On exit, the array +* AP is overwritten by the upper triangular part of the +* updated matrix. +* 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. On exit, the array +* AP is overwritten by the lower triangular part of the +* updated matrix. +* +* 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 ZERO + PARAMETER (ZERO=0.0E+0) +* .. +* .. Local Scalars .. + REAL TEMP + INTEGER I,INFO,IX,J,JX,K,KK,KX +* .. +* .. 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 = 5 + END IF + IF (INFO.NE.0) THEN + CALL XERBLA('SSPR ',INFO) + RETURN + END IF +* +* Quick return if possible. +* + IF ((N.EQ.0) .OR. (ALPHA.EQ.ZERO)) RETURN +* +* Set the start point in X if the increment is not unity. +* + IF (INCX.LE.0) THEN + KX = 1 - (N-1)*INCX + ELSE IF (INCX.NE.1) THEN + KX = 1 + END IF +* +* Start the operations. In this version the elements of the array AP +* are accessed sequentially with one pass through AP. +* + KK = 1 + IF (LSAME(UPLO,'U')) THEN +* +* Form A when upper triangle is stored in AP. +* + IF (INCX.EQ.1) THEN + DO 20 J = 1,N + IF (X(J).NE.ZERO) THEN + TEMP = ALPHA*X(J) + K = KK + DO 10 I = 1,J + AP(K) = AP(K) + X(I)*TEMP + K = K + 1 + 10 CONTINUE + END IF + KK = KK + J + 20 CONTINUE + ELSE + JX = KX + DO 40 J = 1,N + IF (X(JX).NE.ZERO) THEN + TEMP = ALPHA*X(JX) + IX = KX + DO 30 K = KK,KK + J - 1 + AP(K) = AP(K) + X(IX)*TEMP + IX = IX + INCX + 30 CONTINUE + END IF + JX = JX + INCX + KK = KK + J + 40 CONTINUE + END IF + ELSE +* +* Form A when lower triangle is stored in AP. +* + IF (INCX.EQ.1) THEN + DO 60 J = 1,N + IF (X(J).NE.ZERO) THEN + TEMP = ALPHA*X(J) + K = KK + DO 50 I = J,N + AP(K) = AP(K) + X(I)*TEMP + K = K + 1 + 50 CONTINUE + END IF + KK = KK + N - J + 1 + 60 CONTINUE + ELSE + JX = KX + DO 80 J = 1,N + IF (X(JX).NE.ZERO) THEN + TEMP = ALPHA*X(JX) + IX = JX + DO 70 K = KK,KK + N - J + AP(K) = AP(K) + X(IX)*TEMP + IX = IX + INCX + 70 CONTINUE + END IF + JX = JX + INCX + KK = KK + N - J + 1 + 80 CONTINUE + END IF + END IF +* + RETURN +* +* End of SSPR . +* + END |