geqrf_batch (Buffer Strided Version)

oneMKL - Data Parallel C++ Developer Reference

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ID 772045

Date 6/24/2024

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geqrf_batch (Buffer Strided Version)

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

Description
API

Description

The routine forms the Q_iR_i factorizations of a general m-by-n matrices A_i. No pivoting is performed.

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

API

Syntax

namespace oneapi::mkl::lapack {
  void geqrf_batch(sycl::queue &queue,
  int64_t m,
  int64_t n,
  sycl::buffer<T> &a,
  int64_t lda,
  int64_t stride_a,
  sycl::buffer<T> &tau,
  int64_t stride_tau,
  int64_t batch_size,
  sycl::buffer<T> &scratchpad, int64_t scratchpad_size)
}

This function supports the following precisions and devices:

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

*Hybrid support; some computations are performed on the CPU.

Input Parameters

queue: Device queue where calculations will be performed.
m: The number of rows in the matrices A_i (m ≥ 0).
n: The number of columns in the matrices A_i (n ≥ 0).
a: Array holding input matrices A_i.
lda: The leading dimension of A_i (lda ≥ max(1, m)).
stride_a: The stride between the beginnings of matrices A_i inside the batch array a (stride_a ≥ max(1, lda * n)).
stride_tau: The stride between the beginnings of arrays tau_i inside the array tau (stride_tau ≥ max(1, min(m,n))).
batch_size: The number of problems in a batch (batch_size ≥ 0).
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 geqrf_batch_scratchpad_size (Strided Version).

Output Parameters

a

Overwritten by the factorization data as follows:

The elements on and above the diagonal of the array contain the min(m,n)-by-n upper trapezoidal matrices R_i (R_i is upper triangular if m ≥ n); the elements below the diagonal, with the array tau_i, present the orthogonal matrix Q_i as a product of min(m,n) elementary reflectors.

tau

Array to store batch of tau_i, each of size min(m,n), containing scalars that define elementary reflectors for the matrices Q_i in its decomposition in a product of elementary reflectors.

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 than the value returned by the `detail()` method of the exception object.

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 than the value returned by the detail() method of the exception object.

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oneMKL - Data Parallel C++ Developer Reference

geqrf_batch (Buffer Strided Version)

Description

API