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 {
cl::sycl::event geqrf(cl::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<cl::sycl::event> &events = {})
}
gerqf
(USM version) supports the following precisions and
devices:T | Devices supported |
---|---|
float | Host, CPU, and GPU |
double | Host, CPU, and GPU |
std::complex<float> | Host, CPU, and GPU |
std::complex<double> | Host, CPU, and GPU |
Input Parameters
- queue
- Device queue where calculations will be performed.
- m
- The number of rows in the matrixA(0≤m).
- n
- The number of columns in the matrixA(0≤n).
- a
- Pointer to the memory holding input matrixA. The second dimension ofamust be at leastmax(1, n).
- lda
- The leading dimension ofa, 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 typeT. 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 themin(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 leastmin(m,n).Contains scalars that define elementary reflectors for the matrixQin 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 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. |
Return Values
Output event to wait on to ensure computation is complete.