ungqr_batch (Group Version)

oneMKL - Data Parallel C++ Developer Reference

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ID 772045

Date 3/22/2024

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ungqr_batch (Group Version)

Generates the complex unitary matrices Q_i of the batch of QR factorizations formed by geqrf_batch. This routine belongs to the oneapi::mkl::lapack namespace.

Description
API

Description

The routine generates the wholes or parts of m-by-m unitary matrix Q_i of the QR factorization formed by the geqrf_batch (Group Version) function.

Usually Q_i is determined from the QR factorization of an m by p matrix A_i with m ≥ p. To compute the whole matrices Q_i, use:

ungqr_batch(queue, m, m, p, a, ...)

To compute the leading p columns of Q_i (which form an orthonormal basis in the space spanned by the columns of A_i):

ungqr_batch(queue, m, p, p, a, ...)

To compute the matrix Q_i^k of the QR factorization of the leading k columns of the matrices A_i:

ungqr_batch(queue, m, m, k, a, ...)

To compute the leading k columns of Q_i^k (which form an orthonormal basis in the space spanned by the leading k columns of the matrices A_i):

ungqr_batch(queue, m, k, k, a, ...)

API

Syntax

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

This function supports the following precisions and devices:

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

*Interface support only; all computations are performed on the CPU.

Input Parameters

queue: Device queue where calculations will be performed.
m: Array of group_count parameters m_g as previously supplied to geqrf_batch (Group Version) (m_g ≥ 0).
n: Array of group_count parameters n_g as previously supplied to geqrf_batch (Group Version) (n_g ≥ 0).
k: Array of group_count parameters k_g. The number of elementary reflectors whose product defines the matrices Q_i (0 ≤ k_g ≤ n_g) .
a: Array resulting after a call to geqrf_batch (Group Version).
lda: Array of leading dimension of A_i as previously supplied to geqrf_batch (Group Version) (lda_g ≥ max(1, m_g)).
tau: Array resulting after a call to geqrf_batch (Group Version).
group_count: Specifies the number of groups of parameters. Must be at least 0.
group_sizes: Array of group_count integers. Array element with index g specifies the number of problems to solve for each of the groups of parameters g. So the total number of problems to solve, batch_size, is a sum of all parameter group sizes.
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 then the value returned by ungqr_batch_scratchpad_size (Group Version).
events: List of events to wait for before starting computation. Defaults to empty list.

Output Parameters

a: Matrices pointed to by array a are overwritten by n_g leading columns of the m_g-by-m_g unitary matrices Q_i, where g is an index of group of parameters corresponding to Q_i.

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.

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.

Return Values

Output event to wait on to ensure computation is complete.

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oneMKL - Data Parallel C++ Developer Reference

ungqr_batch (Group Version)

Description

API