geqrf#
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 {
void geqrf(sycl::queue &queue,
int64_t m,
int64_t n,
sycl::buffer<T> &a,
int64_t lda,
sycl::buffer<T> &tau,
sycl::buffer<T> &scratchpad,
int64_t scratchpad_size)
}
geqrf 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
A(0 ≤ n).- a
Buffer holding input matrix
A. The size ofamust be at leastlda*n.- lda
The leading dimension of a; at least max(1, m).
- scratchpad
Buffer holding 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 the geqrf_scratchpad_size function.
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 if m ≥ n); the elements below the diagonal, with the array tau, present the orthogonal matrixQas a product of min(m,n) elementary reflectors.- tau
Array, size at least max (1, min(
m,n)). Contains scalars that define elementary reflectors for the matrixQin 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 |