Digital

Name

dmatvec_sdia − Matrix-vector product for symmetric diagonal storage (Serial and Parallel Versions)

FORMAT

DMATVEC_SDIA (job, a, ia, ndim, nz, w, x, y, n )

Arguments

jobinteger∗4
On entry, defines the operation to be performed:

job = 0 : y = A ∗ x

job = 1 : y = transp(A) ∗ x

job = 2 : y = w - A ∗ x

job = 3 : y = w - transp(A) ∗ x
On exit, job is unchanged. 

areal∗8
On entry, a two-dimensional array with dimensions ndim by nz containing the nonzero elements of the matrix A.
On exit, a is unchanged. 

iainteger∗4
On entry, a one-dimensional array of length at least nz,  containing the distances of the diagonals from the main diagonal.
On exit, ia is unchanged. 

ndiminteger∗4
On entry, the leading dimension of array A, as declared in the calling subprogram; ndim >= n.
On exit, ndim is unchanged. 

nzinteger∗4
On entry, the number of diagonals stored in array A.
On exit, nz is unchanged. 

wreal∗8
On entry, a one-dimensional array of length at least n  containing the vector w when job = 2 or 3. The elements are accessed with unit increment. When job = 0 or 1, array W is not needed so w can be a dummy parameter. 
On exit, w is unchanged. 

xreal∗8
On entry, a one-dimensional array of length at least n, containing the elements of vector x, accessed with unit increment.
On exit, x is unchanged. 

yreal∗8
On entry, a one-dimensional array of length at least n.
On exit, array Y is overwritten by the output vector y. The elements of array Y are accessed with unit increment.

ninteger∗4
On entry, the order of the matrix A.
On exit, n is unchanged. 

Description

DMATVEC_SDIA obtains the matrix-vector product for a sparse matrix stored using the symmetric diagonal storage scheme. Depending on the value of the input parameter job, either the matrix or its transpose is used in the operation. 

This routine is available in both serial and parallel versions. The routine names and parameter list are identical for both versions. For information about linking to the serial or to the parallel library, refer to the DXML Reference Manual.