# psb_spmm — Sparse Matrix by Dense Matrix Product

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#### 4.12 psb_spmm — Sparse Matrix by Dense Matrix Product

This subroutine computes the Sparse Matrix by Dense Matrix Product:

| (1)

| (2)

| (3)

where:

x
  is the global dense matrix x:,:
y
  is the global dense matrix y:,:
A
  is the global sparse matrix A

A, x, y, α, β | Subroutine

Short Precision Real | psb_spmm
Long Precision Real | psb_spmm
Short Precision Complex | psb_spmm
Long Precision Complex | psb_spmm

Table 12: Data types

call psb_spmm(alpha, a, x, beta, y, desc_a, info)
call psb_spmm(alpha, a, x, beta, y,desc_a, info, &
& trans, work)

Type:
  Synchronous.
On Entry
alpha
  the scalar α.
  Scope: global
  Type: required
  Intent: in.
  Specified as: a number of the data type indicated in Table 12.
a
  the local portion of the sparse matrix A.
  Scope: local
  Type: required
  Intent: in.
  Specified as: an object of type psb_Tspmat_type.
x
  the local portion of global dense matrix x.
  Scope: local
  Type: required
  Intent: in.
  Specified as: a rank one or two array or an object of type psb_T_vect_type containing numbers of type specified in Table 12. The rank of x must be the same of y.
beta
  the scalar β.
  Scope: global
  Type: required
  Intent: in.
  Specified as: a number of the data type indicated in Table 12.
y
  the local portion of global dense matrix y.
  Scope: local
  Type: required
  Intent: inout.
  Specified as: a rank one or two array or an object of type psb_T_vect_type containing numbers of type specified in Table 12. The rank of y must be the same of x.
desc_a
  contains data structures for communications.
  Scope: local
  Type: required
  Intent: in.
  Specified as: an object of type psb_desc_type.
trans
  indicates what kind of operation to perform.
  trans = N
    the operation is specified by equation 1
  trans = T
    the operation is specified by equation 2
  trans = C
    the operation is specified by equation 3

  Scope: global
  Type: optional
  Intent: in.
  Default: trans = N
  Specified as: a character variable.

work
  work array.
  Scope: local
  Type: optional
  Intent: inout.
  Specified as: a rank one array of the same type of x and y with the TARGET attribute.
On Return
y
  the local portion of result matrix y.
  Scope: local
  Type: required
  Intent: inout.
  Specified as: an array of rank one or two containing numbers of type specified in Table 12.
info
  Error code.
  Scope: local
  Type: required
  Intent: out.
  An integer value; 0 means no error has been detected.

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