## Developer Reference

• 2020.2
• 07/15/2020
• Public Content
Contents

# p?gesv

Computes the solution to the system of linear equations with a square distributed matrix and multiple right-hand sides.

## Syntax

Include Files
Description
The
p?gesv
routine
computes the solution to a real or complex system of linear equations
sub(
A
)*
X
= sub(
B
)
, where
sub(
A
) =
A
(
ia:ia+n-1
,
ja:ja+n-1
)
is an
n
-by-
n
distributed matrix and
X
and
sub(
B
) =
B
(
ib:ib+n-1
,
jb:jb+nrhs-1
)
are
n
-by-
nrhs
distributed matrices.
The
LU
decomposition with partial pivoting and row interchanges is used to factor sub(
A
) as
sub(
A
) =
P
*
L
*
U
, where
P
is a permutation matrix,
L
is unit lower triangular, and
U
is upper triangular.
L
and
U
are stored in sub(
A
). The factored form of sub(
A
) is then used to solve the system of equations
sub(
A
)*
X
= sub(
B
)
.
Input Parameters
n
(global)
INTEGER
.
The number of rows and columns to be operated on, that is, the order of the distributed submatrix
sub(
A
) (
n
0)
.
nrhs
(global)
INTEGER
.
The number of right hand sides, that is, the number of columns of the distributed submatrices
B
and
X
(
nrhs
0)
.
a
,
b
(local)
REAL
for
psgesv
DOUBLE PRECISION
for
pdgesv
COMPLEX
for
pcgesv
DOUBLE COMPLEX
for
pzgesv
.
Pointers into the local memory to arrays of local size
a
(
lld_a
,
LOCc
(
ja
+
n
-1))
and
b
(
lld_b
,
LOCc
(
jb+nrhs-1
))
, respectively.
On entry, the array
a
contains the local pieces of the
n
-by-
n
distributed matrix sub(
A
) to be factored.
On entry, the array
b
contains the right hand side distributed matrix sub(
B
).
ia
,
ja
(global)
INTEGER
.
The row and column indices in the global matrix
A
indicating the first row and the first column of sub(
A
), respectively.
desca
(global and local)
INTEGER
array of size
dlen_
. The array descriptor for the distributed matrix
A
.
ib
,
jb
(global)
INTEGER
.
The row and column indices in the global matrix
B
indicating the first row and the first column of sub(
B
), respectively.
descb
(global