# mkl_dcoosymv

Computes matrix - vector product of a sparse symmetrical matrix stored in the coordinate format with one-based indexing.

## Syntax

Fortran:

call mkl_dcoosymv(uplo, m, val, rowind, colind, nnz, x, y)

C:

mkl_dcoosymv(&uplo, &m, val, rowind, colind, &nnz, x, y);

## Description

The mkl_dcoosymv routine performs a matrix-vector operation defined as
`y := A*x`

or
`y := A'*x,`

where:

x and y are vectors,

A is an upper or lower triangle of the symmetrical sparse matrix in the coordinate format, A' is the transpose of A.

### Note

This routine supports only one-based indexing of the input arrays.

## Input Parameters

Parameter descriptions are common for all implemented interfaces with the exception of data types that refer here to the FORTRAN 77 standard types. Data types specific to the different interfaces are described in the section “Interfaces” below.

uplo

  CHARACTER*1. Specifies whether the upper or low triangle of the matrix A is used.

  If `uplo = 'U'` or 'u', then the upper triangle of the matrix A is used.

  If `uplo = 'L'` or 'l', then the low triangle of the matrix A is used.

m

  INTEGER. Number of rows of the matrix A.

val

  REAL*8. Array of length nnz, contains non-zero elements of the matrix A in the arbitrary order.

  Refer to values array description in Coordinate Format for more details.

rowind

  INTEGER. Array of length nnz, contains the row indices for each non-zero element of the matrix A.

  Refer to rows array description in Coordinate Format for more details.

colind

  INTEGER. Array of length nnz, contains the column indices for each non-zero element of the matrix A. Refer to columns array description in Coordinate Format for more details.

nnz

  INTEGER. Specifies the number of non-zero element of the matrix A.

  Refer to nnz description in Coordinate Format for more details.

x

  REAL*8.

  Array, DIMENSION is m.

  On entry, the array x must contain the vector x.

## Output Parameters

y

  REAL*8.

  Array, DIMENSION at least m.

  On exit, the array y must contain the vector y.

## Interfaces

## FORTRAN 77:

SUBROUTINE mkl_dcoosymv(uplo, m, val, rowind, colind, nnz, x, y)

CHARACTER*1 uplo

INTEGER m, nnz

INTEGER rowind(*), colind(*)

REAL*8 val(*), x(*), y(*)

## C:

`void mkl_dcoosymv(char *uplo, int *m, double *val, int *rowind,`
`int *colind, int *nnz, double *x, double *y);`

Parent topic: Sparse BLAS Level 2 and Level 3 Routines.