Intel® oneAPI Math Kernel Library (oneMKL) - Data Parallel C++ Developer Reference
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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
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. |
Return Values
Output event to wait on to ensure computation is complete.