p?getf2

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 3/31/2023

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p?getf2

Computes an LU factorization of a general matrix, using partial pivoting with row interchanges (local blocked algorithm).

Syntax

void psgetf2 (MKL_INT *m , MKL_INT *n , float *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , MKL_INT *ipiv , MKL_INT *info );

void pdgetf2 (MKL_INT *m , MKL_INT *n , double *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , MKL_INT *ipiv , MKL_INT *info );

void pcgetf2 (MKL_INT *m , MKL_INT *n , MKL_Complex8 *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , MKL_INT *ipiv , MKL_INT *info );

void pzgetf2 (MKL_INT *m , MKL_INT *n , MKL_Complex16 *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , MKL_INT *ipiv , MKL_INT *info );

Include Files

mkl_scalapack.h

Description

The p?getf2function computes an LU factorization of a general m-by-n distributed matrix sub(A) = A(ia:ia+m-1, ja:ja+n-1) using partial pivoting with row interchanges.

The factorization has the form sub(A) = P * L* U, where P is a permutation matrix, L is lower triangular with unit diagonal elements (lower trapezoidal if m>n), and U is upper triangular (upper trapezoidal if m < n). This is the right-looking Parallel Level 2 BLAS version of the algorithm.

Product and Performance Information
Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex. Notice revision #20201201

Product and Performance Information

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

Notice revision #20201201

Input Parameters

m

(global)

The number of rows in the distributed matrix sub(A). (m≥0).

n

(global) The number of columns in the distributed matrix sub(A). (nb_a - mod(ja-1, nb_a)≥n≥0).

a

(local).

Pointer into the local memory to an array of size lld_a * LOC_c(ja+n-1).

On entry, this array contains the local pieces of the m-by-n distributed matrix sub(A).

ia, ja

(global) The row and column indices in the global matrix A indicating the first row and the first column of the matrix sub(A), respectively.

desca

(global and local) array of size dlen_. The array descriptor for the distributed matrix A.

Output Parameters

ipiv

(local)

Array of size(LOCr(m_a) + mb_a). This array contains the pivoting information. ipiv[i] -> The global row that local row (i +1) was swapped with, i = 0, 1, ... , LOCr(m_a) + mb_a - 1. This array is tied to the distributed matrix A.

info

(local).

If info = 0: successful exit.

If 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.

If info > 0: If info = k, the matrix element U(ia+k-1, ja+k-1) is exactly zero. The factorization has been completed, but the factor U is exactly singular, and division by zero will occur if it is used to solve a system of equations.

Parent topic: ScaLAPACK Auxiliary Routines

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p?getf2

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