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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(sycl::queue &queue,
std::int64_t m,
std::int64_t n,
std::int64_t k,
sycl::buffer<T> &a,
std::int64_t lda,
sycl::buffer<T> &tau,
sycl::buffer<T> &scratchpad,
std::int64_t scratchpad_size)
}
orgqr supports the following precisions and devices:
T |
Devices supported |
|---|---|
float |
CPU and GPU |
double |
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 |
|---|---|
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. |