orgbr¶
Generates the real orthogonal matrix Q
or P
T determined
by gebrd. This
routine belongs to the oneapi::mkl::lapack
namespace.
Syntax
-
void
orgbr
(cl::sycl::queue &queue, mkl::generate gen, 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)¶
orgbr
supports the following precisions and devices:
T |
Devices supported |
---|---|
|
Host and CPU |
|
Host and CPU |
Description
The routine generates the whole or part of the orthogonal matrices
Q
and P
T formed by the routines
gebrd. Use this
routine after a call to sgebrd/dgebrd. All valid combinations of
arguments are described in Input parameters. In most cases you need
the following:
To compute the whole m
-by-m
matrix Q
:
orgbr(queue, generate::q, m, m, n, a, …)
(note that the array a
must have at least m
columns).
To form the n
leading columns of Q
if m > n
:
orgbr(queue, generate::q, m, n, n, a, …)
To compute the whole n
-by-n
matrix P
T:
orgbr(queue, generate::p, n, n, m, a, …)
(note that the array a
must have at least n
rows).
To form the m
leading rows of P
T if m < n
:
orgbr(queue, generate::p, m, n, m, a, …)
Input Parameters
- queue
Device queue where calculations will be performed.
- gen
Must be
generate::q
orgenerate::p
.If gen
= generate::q
, the routine generates the matrixQ
.If gen
= generate::p
, the routine generates the matrixP
T.- m
The number of rows in the matrix
Q
orP
T to be returned(0≤m)
.If gen
= generate::q
,m ≥ n ≥ min(m, k)
.If gen
= generate::p
,n ≥ m ≥ min(n, k)
.- n
The number of rows in the matrix
Q
orP
T to be returned(0≤n)
. See m for constraints.- k
If gen
= generate::q
, the number of columns in the originalm
-by-k matrix reduced by gebrd.If gen
= generate::p
, the number of rows in the originalk
-by-n matrix reduced by gebrd.- a
Buffer holding memory returned by gebrd.
- lda
The leading dimension of a.
- tau
Buffer holding array of size
min (m,k)
if gen= generate::q
, and of sizemin(n,k)
if gen= generate::p
. Scalar factor of the elementary reflectors, as returned by gebrd in the array tauq or taup.- 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 orgbr_scratchpad_size function.
Output Parameters
- a
Overwritten by n leading columns of the m-by-m orthogonal matrix
Q
orP
T (or the leading rows or columns thereof) as specified by gen, m, and n.
Exceptions
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 |