Intel® oneAPI Math Kernel Library (oneMKL) - Data Parallel C++ Developer Reference

Developer Reference

Contents

orgtr

Generates the real orthogonal matrix Q determined by sytrd. This routine belongs to the
oneapi::mkl::lapack
 namespace.

Description

The routine explicitly generates the
n
-by-
n
 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.

API

Syntax
namespace oneapi::mkl::lapack {
  void orgtr(cl::sycl::queue &queue,
  mkl::uplo uplo,
  std::int64_t n,
  cl::sycl::buffer<T> &a,
  std::int64_t lda,
  cl::sycl::buffer<T> &tau,
  cl::sycl::buffer<T> &scratchpad,
  std::int64_t scratchpad_size)
}
orgtr
 supports the following precisions and devices:
T
Devices supported
float
Host and CPU
double
Host and CPU
Input Parameters
queue
Device queue where calculations will be performed.
uplo
Must be uplo::upper or uplo::lower. Uses the same uplo as supplied to the sytrd function
n
The order of matrix
Q
 (
0≤n
).
a
The buffer
a
 returned by the sytrd function. The second dimension of
a
 must be at least
max(1, n)
.
lda
The leading dimension of
a
 (
n≤lda
).
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 orgtr_scratchpad_size function.
Output Parameters
a
Overwritten by the 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.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.