gerqf (USM Version)

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

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ID 772045

Date 12/16/2022

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gerqf (USM Version)

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

Description
API

Description

The routine forms the RQ factorization of a general m-by-n matrix A. No pivoting is performed.

The routine does not form the matrix Q explicitly. Instead, Q is represented as a product of min(m, n) elementary reflectors. Routines are provided to work with Q in this representation.

API

Syntax

namespace oneapi::mkl::lapack {
  sycl::event gerqf(sycl::queue &queue,
  std::int64_t m,
  std::int64_t n,
  T *a,
  std::int64_t lda,
  T *tau,
  T *scratchpad,
  std::int64_t scratchpad_size,
  const std::vector<sycl::event> &events = {})
}

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

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

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 memory holding input matrix A. The second dimension of a must be at least max(1, n).
lda: The leading dimension of a, at least max(1, m).
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 gerqf_scratchpad_size function.
events: List of events to wait for before starting computation. Defaults to empty list.

Output Parameters

a

Overwritten by the factorization data as follows:

if m ≤ n, the upper triangle of the subarray a(1:m, n-m+1:n ) contains the m-by-m upper triangular matrix R; if m ≥ n, the elements on and above the (m-n)-th subdiagonal contain the m-by-n upper trapezoidal matrix R

In both cases, the remaining elements, with the arraytau, represent the orthogonal/unitary matrix Q as a product of min(m,n) elementary reflectors.

tau

Array, size at least min(m,n).

Contains scalars that define elementary reflectors for the matrix Q in its decomposition in a product of elementary reflectors.

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 get_info() method of the exception object: If `info = -i`, the `i`-th parameter had an illegal value. If `info` is equal to the value passed as scratchpad size, and get_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 get_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 get_info() method of the exception object:

If info = -i, the i-th parameter had an illegal value.

If info is equal to the value passed as scratchpad size, and get_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 get_detail() method of the exception object.

Return Values

Output event to wait on to ensure computation is complete.

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

gerqf (USM Version)

Description

API