Developer Reference

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getrf_batch (Buffer Strided Version)

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

Description

The routine computes the LU factorizations of a batch of general
m
-by-
n
matrices
A
i
, as:
LaTex Math image.
Where
P
i
is a permutation matrix,
L
i
is lower triangular with unit diagonal elements (lower trapezoidal if
m > n
) and
U
i
is upper triangular (upper trapezoidal if
m < n
). The routine uses partial pivoting with row interchanges.

API

Syntax
namespace oneapi::mkl::lapack { void getrf_batch( cl::sycl::queue &queue, std::int64_t m, std::int64_t n, cl::sycl::buffer<T> &a, std::int64_t lda, std::int64_t stride_a, cl::sycl::buffer<std::int64_t> &ipiv, std::int64_t stride_ipiv, std::int64_t batch_size, cl::sycl::buffer<T> &scratchpad, std::int64_t scratchpad_size) }
Function 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
Input Parameters
queue
Device queue where calculations will be performed.
m
The number of rows in the matrices
A
i
(
0 ≤ m
).
n
The number of columns in the matrices
A
i
(
0 ≤ n
).
a
Array holding input matrices
A
i
.
lda
The leading dimension of
A
i
.
stride_a
The stride between the beginnings of matrices
A
i
inside the batch array
a
.
stride_ipiv
The stride between the beginnings of arrays
ipiv
i
inside the array
ipiv
.
batch_size
Specifies the number of problems in a batch.
scratchpad
Scratchpad memory to be used by 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 getrf_batch_scratchpad_size (Strided Version).
Output Parameters
a
Overwritten by
L
i
and
U
i
. The unit diagnonal elements of
L
i
are not stored.
ipiv
Array containing the batch of the pivot indices
ipiv
i
each of size at least
max(1,min(m,n))
; for 1 ≤
k
min(m,n)
, row
k
of
A
i
was interchanged with row
ipiv
i
(
k
).
Exceptions
Exception
Description
mkl::lapack::batch_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 = -n
, the
n
-th parameter had an illegal value.
If
info
equals the value passed as scratchpad size, and detail() returns non-zero, then the passed scratchpad is of insufficient size, and the required size should be not less then value returned by the detail() method of the exception object.
If
info
is zero, then the diagonal element of some of
U
i
is zero, and the solve could not be completed. The indexes of such matrices in the batch can be obtained with the ids() method of the exception object. You can obtain the indexes of the first zero diagonal elements in these
U
i
matrices using the infos() method of the exception object.

Product and Performance Information

1

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