gesv (USM Version)

oneMKL - Data Parallel C++ Developer Reference

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ID 772045

Date 7/13/2023

Version

Public

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gesv (USM Version)

Computes the solution to the system of linear equations with a square coefficient matrix and multiple right-hand sides. This routine belongs to the oneapi::mkl::lapack namespace.

Description
API

Description

The routine solves for X the system of linear equations A*X = B, where A is an n-by-n matrix, the columns of matrix B are individual right-hand sides, and the columns of X are the corresponding solutions.

The LU decomposition with partial pivoting and row interchanges is used to factor A as A = P*L*U, where P is a permutation matrix, L is unit lower triangular, and U is upper triangular. The factored form of A is then used to solve the system of equations A*X = B.

API

Syntax

namespace oneapi::mkl::lapack {
  sycl::event gesv(sycl::queue &queue,
  std::int64_t n,
  std::int64_t nrhs,
  T *a,
  std::int64_t lda,
  std::int64_t *ipiv,
  T *b,
  std::int64_t ldb,
  T *scratchpad,
  std::int64_t scratchpad_size,
  const std::vector<sycl::event> &events = {})
}

gesv (USM version) supports the following precisions and devices:

T	Devices supported
`float`	CPU, GPU
`double`	CPU, GPU
`std::complex<float>`	CPU, GPU
`std::complex<double>`	CPU, GPU

Input Parameters

queue: Device queue where calculations will be performed.
n: The order of the matrix A; (0 ≤ n).
nrhs: The number of right-hand sides (0 ≤ nrhs).
a: Pointer to the n-by-n coefficient matrix A.
lda: The leading dimension of a.
b: Pointer to the n-by-nrhs matrix of right hand side matrix B
ldb: The leading dimension of b.
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 gesv_scratchpad_size function.
events: List of events to wait for before starting computation. Defaults to empty list.

Output Parameters

a: Overwritten by the factors L and U from the factorization of A = P*L*U; the unit diagonal elements of L are not stored.
b: The buffer b is overwritten by the solution matrix X.
ipiv: Array, size at least max(1, n). The ipiv array, as returned by getrf (USM Version).

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`, the `i`-th diagonal element of `U` is zero, and the solve could not be completed. 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.

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, the i-th diagonal element of U is zero, and the solve could not be completed.

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.

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oneMKL - Data Parallel C++ Developer Reference

gesv (USM Version)

Description

API