Intel® oneAPI Math Kernel Library (oneMKL) - Data Parallel C++ Developer Reference

Developer Reference

Contents

getrf (USM Version)

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

Description

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

API

Syntax
namespace oneapi::mkl::lapack {
  cl::sycl::event getrf(cl::sycl::queue &queue,
  std::int64_t m,
  std::int64_t n,
  T *a,
  std::int64_t lda,
  std::int64_t *ipiv,
  T *scratchpad,
  std::int64_t scratchpad_size,
  const std::vector<cl::sycl::event> &events = {})
}
getrf
 (USM version) supports the following precisions and devices:
T
Devices supported
float
Host, CPU, GPU
double
Host, CPU, GPU
std::complex<float>
Host, CPU, GPU
std::complex<double>
Host, CPU, GPU
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 the matrix
A
 (
0≤n
).
a
Pointer to the array holding input matrix
A
. The second dimension of
a
 must be at least
max(1, n)
.
lda
The leading dimension of
a
.
scratchpad
Pointer to 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.
events
List of events to wait for before starting computation. Defaults to empty list.
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)
.
Exceptions
Exception
Description
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.
Return Values
Output event to wait on to ensure computation is complete.

Product and Performance Information

1

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