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geqrf_batch (USM Strided Version)
Computes the batch of QR factorizations of a batch of general m-by-n matrices. This routine belongs to the oneapi::mkl::lapack namespace.
Description
The routine forms the QiRi factorizations of a general m-by-n matrix Ai. No pivoting is performed.
The routine does not form the matrix Qi explicitly. Instead, Qi is represented as a product of min(m, n) elementary reflectors. Routines are provided to work with Qi in this representation.
API
Syntax
namespace oneapi::mkl::lapack {
sycl::event geqrf_batch(sycl::queue &queue,
int64_t m,
int64_t n,
T *a,
int64_t lda,
int64_t stride_a,
T *tau,
int64_t stride_tau,
int64_t batch_size,
T *scratchpad,
int64_t scratchpad_size,
const std::vector<sycl::event> &events = {})
}This function supports the following precisions and devices:
T |
Devices supported |
|---|---|
float |
CPU and GPU* |
double |
CPU and GPU* |
std::complex<float> |
CPU and GPU* |
std::complex<double> |
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 matrices Ai (m ≥ 0).
- n
-
The number of columns in the matrices Ai (n ≥ 0).
- a
-
Array holding input matrices Ai.
- lda
-
The leading dimension of Ai (lda ≥ max(1, m)).
- stride_a
-
The stride between the beginnings of matrices Ai inside the batch array a (stride_a ≥ max(1, lda * n)).
- stride_tau
-
The stride between the beginnings of arrays taui inside the array tau (stride_tau ≥ max(1, min(m,n))).
- batch_size
-
The number of problems in a batch (batch_size ≥ 0).
- scratchpad
-
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 than the value returned by geqrf_batch_scratchpad_size (Strided Version).
- 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-n upper trapezoidal matrices Ri (Ri is upper triangular if m ≥ n); the elements below the diagonal, with the array taui, present the orthogonal matrix Qi as a product of min(m,n) elementary reflectors.
- tau
-
Array to store batch of taui, each of size min(m,n), containing scalars that define elementary reflectors for the matrices Qi in its decomposition in a product of elementary reflectors.
Exceptions
Exception |
Description |
|---|---|
mkl::lapack::batch_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 = -n, the n-th parameter had an illegal value. If info equals the value passed as scratchpad size, and detail() returns non-zero, then the passed scratchpad is of insufficient size, and the required size should be not less then value returned by the detail() method of the exception object. |
Return Values
Output event to wait on to ensure computation is complete.