# mkl_ddiamm

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

## Syntax

Fortran:

call mkl_ddiamm(transa, m, n, k, alpha, matdescra, val, lval, idiag, ndiag, b, ldb, beta, c, ldc)

C:

mkl_ddiamm(&transa, &m, &n, &k, &alpha, matdescra, val, &lval, idiag, &ndiag, b, &ldb, &beta, c, &ldc);

## Description

The mkl_ddiamm routine performs a matrix-matrix operation defined as
`C := alpha*A*B + beta*C`

or
`C := alpha*A'*B + beta*C,`

where:

alpha and beta are scalars,

B and C are dense matrices, A is an m-by-k sparse matrix in the diagonal 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.

transa

  CHARACTER*1. Specifies the operation.

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

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

m

  INTEGER. Number of rows of the matrix A.

n

  INTEGER. Number of columns of the matrix C.

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. Two-dimensional array of size lval by ndiag, contains non-zero diagonals of the matrix A. Refer to values array description in Diagonal Storage Scheme for more details.

lval

  INTEGER. Leading dimension of val, `lval≥m`. Refer to lval description in Diagonal Storage Scheme for more details.

idiag

  INTEGER. Array of length ndiag, contains the distances between main diagonal and each non-zero diagonals in the matrix A.

  Refer to distance array description in Diagonal Storage Scheme for more details.

ndiag

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

b

  REAL*8.

  Array, DIMENSION `(ldb, n)`.

  On entry with `transa = 'N'` or 'n', the leading k-by-n part of the array b must contain the matrix B, otherwise the leading m-by-n part of the array b must contain the matrix B.

ldb

  INTEGER. Specifies the first dimension of b as declared in the calling (sub)program.

beta

  REAL*8. Specifies the scalar beta.

c

  REAL*8.

  Array, DIMENSION (ldc, n).

  On entry, the leading m-by-n part of the array c must contain the matrix C, otherwise the leading k-by-n part of the array c must contain the matrix C.

ldc

  INTEGER. Specifies the first dimension of c as declared in the calling (sub)program.

## Output Parameters

c

  Overwritten by the matrix `(alpha*A*B + beta*C)` or `(alpha*A'*B + beta*C)`.

## Interfaces

## FORTRAN 77:

SUBROUTINE mkl_ddiamm(transa, m, n, k, alpha, matdescra, val, lval,

idiag, ndiag, b, ldb, beta, c, ldc)

CHARACTER*1 transa

CHARACTER matdescra(*)

INTEGER m, n, k, ldb, ldc, lval, ndiag

INTEGER idiag(*)

REAL*8 alpha, beta

REAL*8 val(lval,*), b(ldb,*), c(ldc,*)

## C:

`void mkl_ddiamm(char *transa, int *m, int *n, int *k, double *alpha,`
`char *matdescra, double *val, int *lval, int *idiag, int *ndiag,`
`double *b, int *ldb, double *beta, double *c, int *ldc);`

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