orgqr¶
Generates the real orthogonal matrix Q of the QR factorization formed by
geqrf. This routine belongs to the oneapi::mkl::lapack namespace.
Description¶
The routine generates the whole or part of m-by-m orthogonal
matrix Q of the QR factorization formed by the routine
geqrf.
Usually Q is determined from the QR factorization of an m
by p matrix A with m≥p. To compute the whole matrix
Q, use:
mkl::orgqr(queue, m, m, p, a, lda, tau, ...)
To compute the leading p columns of Q (which form an
orthonormal basis in the space spanned by the columns of A):
mkl::orgqr(queue, m, p, p, a, lda, tau, ...)
To compute the matrix Qk of the QR factorization of
leading k columns of the matrix A:
mkl::orgqr(queue, m, m, k, a, lda, tau, ...)
To compute the leading k columns of Qk (which form
an orthonormal basis in the space spanned by leading k columns of
the matrix A):
mkl::orgqr(queue, m, k, k, a, lda, tau, ...)
API¶
Syntax¶
namespace oneapi::mkl::lapack {
void orgqr(cl::sycl::queue &queue,
std::int64_t m,
std::int64_t n,
std::int64_t k,
cl::sycl::buffer<T> &a,
std::int64_t lda,
cl::sycl::buffer<T> &tau,
cl::sycl::buffer<T> &scratchpad,
std::int64_t scratchpad_size)
}
orgqr supports the following precisions and devices:
T |
Devices supported |
|---|---|
|
Host, CPU, and GPU |
|
Host, CPU, and GPU |
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).- k
The number of elementary reflectors whose product defines the matrix
Q(0≤k≤n).- a
Buffer holding the result of geqrf.
- lda
The leading dimension of a (
lda≤m).- tau
Buffer holding the result of geqrf.
- scratchpad
Buffer holding 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 orgqr_scratchpad_size function.
Output Parameters¶
- a
Overwritten by n leading columns of the m-by-m orthogonal matrix
Q.
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 |