Visible to Intel only — GUID: GUID-AD67A816-AAFA-4CFC-B933-3743206C3AE4
Visible to Intel only — GUID: GUID-AD67A816-AAFA-4CFC-B933-3743206C3AE4
ungqr
Generates the complex unitary matrix Q of the QR factorization formed by geqrf. This routine belongs to the oneapi::mkl::lapack namespace.
Description
The routine generates the whole or part of m-by-m unitary matrix Q of the QR factorization formed by the routines geqrf.
Usually Q is determined from the QR factorization of an m by p matrix A with m ≥ p. To compute the whole matrix Q, use:
mkl::ungqr(queue, m, m, p, a, lda, tau, ...)
To compute the leading p columns of Q (which form an orthonormal basis in the space spanned by the columns of A):
mkl::ungqr(queue, m, p, p, a, lda, tau, ...)
To compute the matrix Qk of the QR factorization of the leading k columns of the matrix A:
mkl::ungqr(queue, m, m, k, a, lda, tau, ...)
To compute the leading k columns of Qk (which form an orthonormal basis in the space spanned by the leading k columns of the matrix A):
mkl::ungqr(queue, m, k, k, a, lda, tau, ...)
API
Syntax
namespace oneapi::mkl::lapack { void ungqr(sycl::queue &queue, std::int64_t m, std::int64_t n, std::int64_t k, sycl::buffer<T> &a, std::int64_t lda, sycl::buffer<T> &tau, sycl::buffer<T> &scratchpad, std::int64_t scratchpad_size) }
ungqr`` supports the following precisions and devices:
T |
Devices supported |
---|---|
std::complex<float> |
CPU and GPU |
std::complex<double> |
CPU and GPU |
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).
- k
-
The number of elementary reflectors whose product defines the matrix Q (0 ≤ k ≤ n).
- a
-
Buffer holding the result of geqrf.
- lda
-
The leading dimension of A (lda ≥ m).
- tau
-
Buffer holding the result of geqrf.
- 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 ungqr_scratchpad_size function.
Output Parameters
- a
-
Overwritten by n leading columns of the m-by-m unitary matrix Q.
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. |