geqrf (USM Version)#
Computes the QR factorization of a general m-by-n matrix. This routine belongs to the oneapi::mkl::lapack namespace.
Description#
The routine forms the QR 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 geqrf(sycl::queue &queue,
int64_t m,
int64_t n,
T *a,
int64_t lda,
T *tau,
T *scratchpad,
int64_t scratchpad_size,
const std::vector<sycl::event> &events = {})
}
geqrf (USM version) supports the following precisions and
devices:
T |
Devices supported |
|---|---|
|
CPU and GPU* |
|
CPU and GPU* |
|
CPU and GPU* |
|
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 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 array must have size at leastlda*n.- lda
The leading dimension of
a, at leastmax(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 geqrf_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:
The elements on and above the diagonal of the array contain the
min(m,n)-by-nupper trapezoidal matrixR(Ris upper triangular ifm ≥ n); the elements below the diagonal, with the array tau, present the orthogonal matrixQas a product ofmin(m,n)elementary reflectors.- tau
Array, size at least
min(m,n).Contains scalars that define elementary reflectors for the matrix
Qin its decomposition in a product of elementary reflectors.
Exceptions#
Exception |
Description |
|---|---|
|
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 If |
Return Values#
Output event to wait on to ensure computation is complete.