getrf

Computes the LU factorization of a general m-by-n matrix. This routine belongs to the oneapi::mkl::lapacknamespace.

Syntax

void getrf(cl::sycl::queue &queue, std::int64_t m, std::int64_t n, cl::sycl::buffer<T> &a, std::int64_t lda, std::int64_t *ipiv, cl::sycl::buffer<T> &scratchpad, std::int64_t scratchpad_size)

getrf supports the following precisions and devices.

T

Devices supported

float

Host, CPU, and GPU

double

Host, CPU, and GPU

std::complex<float>

Host, CPU, and GPU

std::complex<double>

Host, CPU, and GPU

Description

The routine computes the LU factorization of a general m-by-n matrix A as

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). The routine uses partial pivoting, with row interchanges.

Input Parameters

queue

Device queue where calculations will be performed.

m

The number of rows in the matrix A (0≤m).

n

The number of columns in A(0≤n).

a

Buffer holding array holding input matrix A. The second dimension of a must be at least max(1, n).

lda

The leading dimension of a.

scratchpad

Buffer holding scratchpad memory to be used by the routine for storing intermediate results.

scratchpad_size

Size of scratchpad memory as a number of floating point elements of type T. Size should not be less than the value returned by the getrf_scratchpad_size function.

Output Parameters

a

Overwritten by L and U. The unit diagonal elements of L are not stored.

ipiv

Array, size at least max(1,min(m, n)). Contains the pivot indices; for 1 ≤i≤min(m, n),row i was interchanged with row ipiv(i).

info

Buffer containing error information. If info=0, execution is successful. If info=-i, the i-th parameter had an illegal value. If info=i, uii is 0. The factorization has been completed, but U is exactly singular. Division by 0 will occur if you use the factor U for solving a system of linear equations.

Exceptions

mkl::lapack::exception

This exception is thrown when problems occur during calculations. You can obtain the info code of the problem using the info() method of the exception object: If info = -i, the i-th parameter had an illegal value. If info = i, uii is 0. The factorization has been completed, but U is exactly singular. Division by 0 will occur if you use the factor U for solving a system of linear equations. If info is equal to the value passed as scratchpad size, and detail() returns non zero, then the passed scratchpad has an insufficient size, and the required size should not be less than the value returned by the detail() method of the exception object.