Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

p?dttrf

Computes the
LU
 factorization of a diagonally dominant-like tridiagonal distributed matrix.

Syntax

void
psdttrf
(
MKL_INT
*n
,
float
*dl
,
float
*d
,
float
*du
,
MKL_INT
*ja
,
MKL_INT
*desca
,
float
*af
,
MKL_INT
*laf
,
float
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
void
pddttrf
(
MKL_INT
*n
,
double
*dl
,
double
*d
,
double
*du
,
MKL_INT
*ja
,
MKL_INT
*desca
,
double
*af
,
MKL_INT
*laf
,
double
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
void
pcdttrf
(
MKL_INT
*n
,
MKL_Complex8
*dl
,
MKL_Complex8
*d
,
MKL_Complex8
*du
,
MKL_INT
*ja
,
MKL_INT
*desca
,
MKL_Complex8
*af
,
MKL_INT
*laf
,
MKL_Complex8
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
void
pzdttrf
(
MKL_INT
*n
,
MKL_Complex16
*dl
,
MKL_Complex16
*d
,
MKL_Complex16
*du
,
MKL_INT
*ja
,
MKL_INT
*desca
,
MKL_Complex16
*af
,
MKL_INT
*laf
,
MKL_Complex16
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
Include Files
  • mkl_scalapack.h
Description
The
p?dttrf
function
computes the
LU
 factorization of an
n
-by-
n
 real/complex diagonally dominant-like tridiagonal distributed matrix
A
(1:
n
,
ja
:
ja
+
n
-1) without pivoting for stability.
The resulting factorization is not the same factorization as returned from LAPACK. Additional permutations are performed on the matrix for the sake of parallelism.
The factorization has the form:
A
(1:
n
,
ja
:
ja
+
n
-1) =
P*L*U*P
T
,
where
P
 is a permutation matrix, and
L
 and
U
 are banded lower and upper triangular matrices, respectively.
Product and Performance Information
Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.
Notice revision #20201201
Input Parameters
n
(global) The number of rows and columns to be operated on, that is, the order of the distributed submatrix
A
(1:
n
,
ja
:
ja
+
n
-1)
(
n
≥
 0)
.
dl
,
d
,
du
(local)
Pointers to the local arrays of size
nb_a
 each.
On entry, the array
dl
 contains the local part of the global vector storing the subdiagonal elements of the matrix. Globally,
dl
[0]
 is not referenced, and
dl
 must be aligned with
d
.
On entry, the array
d
 contains the local part of the global vector storing the diagonal elements of the matrix.
On entry, the array
du
 contains the local part of the global vector storing the super-diagonal elements of the matrix.
du
[
n
-1]
 is not referenced, and
du
 must be aligned with
d
.
ja
(global) The index in the global matrix
A
 indicating the start of the matrix to be operated on (which may be either all of
A
 or a submatrix of
A
).
desca
(global and local) array of size
dlen_
. The array descriptor for the distributed matrix
A
.
If
dtype_a
 = 501
, then
dlen_
≥
 7
;
else if
dtype_a
 = 1
, then
dlen_
≥
 9
.
laf
(local) The size of the array
af
.
Must be
laf
≥
 2*(
NB
+2) .
If
laf
 is not large enough, an error code will be returned and the minimum acceptable size will be returned in
af
[0]
.
work
(local) Same type as
d
. Workspace array of size
lwork
.
lwork
(local or global) The size of the
work
 array, must be at least
lwork
≥
 8*
NPCOL
.
Output Parameters
dl
,
d
,
du
On exit, overwritten by the information containing the factors of the matrix.
af
(local)
Array of size
laf
.
Auxiliary fill-in space. The fill-in space is created in a call to the factorization
function
p?dttrf
 and is stored in
af
.
Note that if a linear system is to be solved using
p?dttrs
 after the factorization
function
,
af
 must not be altered.
work
[0]
On exit,
work
[0]
 contains the minimum value of
lwork
 required for optimum performance.
info
(global)
If
info
=0
, the execution is successful.
info
 < 0
:
If the
i
-th argument is an array and the
j-
th entry
, indexed
j
 - 1,
 had an illegal value, then
info
 = -(
i
*100+
j
); if the
i-
th argument is a scalar and had an illegal value, then
info
 =
-i
.
info
>
 0
:
If
info
 =
k
 ≤
NPROCS
, the submatrix stored on processor
info
 and factored locally was not diagonally dominant-like, and the factorization was not completed.
If
info
 =
k
 >
NPROCS
, the submatrix stored on processor
info
-
NPROCS
 representing interactions with other processors was not nonsingular, and the factorization was not completed.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.