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unmqr

Multiplies a complex matrix by the unitary matrix Q of the QR factorization formed by unmqr. This routine belongs to the oneapi::mkl::lapack namespace.

Description

The routine multiplies a rectangular complex matrix C by Q or QH, where Q is the unitary matrix Q of the QR factorization formed by the routines geqrf.

Depending on the parameters left_right and trans, the routine can form one of the matrix products Q*C, QH*C, C*Q, or C*QH (overwriting the result on C).

API

Syntax

namespace oneapi::mkl::lapack {
  void unmqr(cl::sycl::queue &queue,
  mkl::side side,
  mkl::transpose trans,
  std::int64_t m,
  std::int64_t n,
  std::int64_t k,
  cl::sycl::buffer<T> &a,
  std::int64_t lda,
  cl::sycl::buffer<T> &tau,
  cl::sycl::buffer<T> &c,
  std::int64_t ldc,
  cl::sycl::buffer<T> &scratchpad,
  std::int64_t scratchpad_size)
}

unmqr supports the following precisions and devices:

T

Devices supported

std::complex<float>

Host, CPU, and GPU

std::complex<double>

Host, CPU, and GPU

Input Parameters

queue

Device queue where calculations will be performed.

side

If side = mkl::side::left, Q or QT is applied to C from the left. If side = mkl::side::right, Q or QT is applied to C from the right.

trans

If trans=mkl::transpose::trans, the routine multiplies C by Q.

If trans=mkl::transpose::nontrans, the routine multiplies C by QT.

m

The number of rows in the matrix A (0≤m).

n

The number of columns in the matrix A (0≤n≤m).

k

The number of elementary reflectors whose product defines the matrix Q (0≤k≤n).

a

Buffer holding the result of the geqrf function. The second dimension of a must be at least max(1,k).

lda

The leading dimension of a.

tau

Buffer holding tau returned by the geqrf function.

c

Buffer holding the matrix C. The second dimension of c must be at least max(1,n).

ldc

The leading dimension of c.

scratchpad

Buffer holding 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 unmqr_scratchpad_size function.

Output Parameters

c

Overwritten by the product Q*C, QT*C, C*Q, or C*QT (as specified by side and trans).

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 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.
ungtr_scratchpad_size unmqr (USM Version)