# mkl_dcoomv

Computes matrix - vector product for a sparse matrix in the coordinate format.

## Syntax

Fortran:

call mkl_dcoomv(transa, m, k, alpha, matdescra, val, rowind, colind, nnz, x, beta, y)

C:

mkl_dcoomv(&transa, &m, &k, &alpha, matdescra, val, rowind, colind, &nnz, x, &beta, y);

## Description

The mkl_dcoomv routine performs a matrix-vector operation defined as
`y := alpha*A*x + beta*y`

or
`y := alpha*A'*x + beta*y,`

where:

alpha and beta are scalars,

x and y are vectors,

A is an m-by-k sparse matrix in compressed coordinate format, A' is the transpose of A.

### Note

This routine supports coordinate format both with one-based indexing and zero-based indexing.

## 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.

transa

  CHARACTER*1. Specifies the operation.

  If `transa = 'N'` or 'n', then `y := alpha*A*x + beta*y`

  If `transa = 'T'` or 't' or 'C' or 'c', then `y := alpha*A'*x + beta*y`,

m

  INTEGER. Number of rows of the matrix A.

k

  INTEGER. Number of columns of the matrix A.

alpha

  REAL*8. Specifies the scalar alpha.

matdescra

  CHARACTER. Array of six elements, specifies properties of the matrix used for operation. Only first four array elements are used, their possible values are given in the “Possible Values of the Parameter matdescra (descra)”.

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 at least k if `transa = 'N'` or 'n' and at least m otherwise. On entry, the array x must contain the vector x.

beta

  REAL*8. Specifies the scalar beta.

y

  REAL*8.

  Array, DIMENSION at least m if `transa = 'N'` or 'n' and at least k otherwise. On entry, the array y must contain the vector y.

## Output Parameters

y

  Overwritten by the updated vector y.

## Interfaces

## FORTRAN 77:

SUBROUTINE mkl_dcoomv(transa, m, k, alpha, matdescra, val, rowind, colind, nnz, x, beta, y)

CHARACTER*1 transa

CHARACTER matdescra(*)

INTEGER m, k, nnz

INTEGER rowind(*), colind(*)

REAL*8 alpha, beta

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

## C:

`void mkl_dcoomv(char *transa, int *m, int *k, double *alpha, char *matdescra,`
`double *val, int *rowind, int *colind, int *nnz, double *x, double *beta, double *y);`

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