ormtr#
Multiplies a real matrix by the real orthogonal matrix Q determined
by sytrd. This routine belongs to the oneapi::mkl::lapack namespace.
Description#
QT, where Q is the orthogonal matrix Q formed by
sytrd when
reducing a real symmetric matrix A to tridiagonal form:
A = Q*T*QT. Use this routine after a call to
sytrd.
Depending on the parameters left_right and trans, the routine can
form one of the matrix products Q*C, QT*C, C*Q, or
C*QT (overwriting the result on C).
The routine multiplies a real matrix C by Q or
API#
Syntax#
namespace oneapi::mkl::lapack {
void ormtr(sycl::queue &queue,
mkl::side side,
mkl::uplo uplo,
mkl::transpose trans,
int64_t m,
int64_t n,
sycl::buffer<T> &a,
int64_t lda,
sycl::buffer<T> &tau,
sycl::buffer<T> &c,
int64_t ldc,
sycl::buffer<T> &scratchpad,
int64_t scratchpad_size)
}
ormtr supports the following precisions and devices:
T |
Devices supported |
|---|---|
|
CPU |
|
CPU |
Input Parameters#
In the descriptions below, r denotes the order of Q:
|
if |
|
if |
- queue
Device queue where calculations will be performed.
- side
Must be either
side::leftorside::right.If
side = side::left,QorQT is applied toCfrom the left.If
side = side::right,QorQT is applied toCfrom the right.- uplo
Must be either
uplo::upperoruplo::lower. Uses the sameuploas supplied to sytrd.- trans
Must be either
transpose::nontransortranspose::trans.If
trans = transpose::nontrans, the routine multipliesCbyQ.If
trans = transpose::trans, the routine multipliesCbyQT.- m
The number of rows in the matrix
C(m ≥ 0).- n
The number of columns in the matrix
C(n ≥ 0).- a
Buffer holding array returned by sytrd.
- lda
The leading dimension of
a(lda ≥ max(1, r)).- tau
Buffer holding tau returned by sytrd. The dimension of tau must be at least
max(1, r-1).- c
Buffer holding the matrix
C. The size ofcmust be at leastldc*n.- ldc
The leading dimension of
c(ldc ≥ max(1, m)).- 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 ormtr_scratchpad_size function.
Output Parameters#
- c
Overwritten by the product
Q*C,QT*C,C*Q, orC*QT(as specified by side and trans).
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 |