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Technical Reference: Base Operating System and Extensions , Volume 2
Performs matrix-vector operations
using a packed symmetric matrix.
BLAS Library
(libblas.a)
SUBROUTINE SSPMV(UPLO, N, ALPHA, AP, X,
INCX, BETA, Y, INCY)
REAL ALPHA, BETA
INTEGER INCX, INCY, N
CHARACTER*1 UPLO
REAL AP(*), X(*), Y(*)
SUBROUTINE DSPMV(UPLO, N, ALPHA, AP, X,
INCX, BETA, Y, INCY)
DOUBLE PRECISION ALPHA,BETA
INTEGER INCX,INCY,N
CHARACTER*1 UPLO
DOUBLE PRECISION AP(*), X(*), Y(*)
The SSPMV or
DSPMV subroutine 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.
| UPLO
| 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
| On entry, N specifies the order of the matrix
A; N must be at least 0; unchanged on
exit.
|
| ALPHA
| On entry, ALPHA specifies the scalar alpha; unchanged on
exit.
|
| AP
| A vector of dimension at least ( ( N * (N+1) )/2
); on 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 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
| A vector of dimension at least (1 + (N-1) * abs(
INCX ) ); on entry, the incremented array X must
contain the N element vector x; unchanged on exit.
|
| INCX
| On entry, INCX specifies the increment for the elements of
X; INCX must not be 0; unchanged on
exit.
|
| BETA
| On entry, BETA specifies the scalar beta; when
BETA is supplied as 0 then Y need not be set on input;
unchanged on exit.
|
| Y
| A vector of dimension at least (1 + (N-1) * abs(
INCY ) ); on entry, the incremented array Y must
contain the N element vector y; on exit, Y is
overwritten by the updated vector y.
|
| INCY
| On entry, INCY specifies the increment for the elements of
Y; INCY must not be 0; unchanged on
exit.
|
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