unmtr

Multiplies a complex matrix by the complex unitary matrix Q determined by hetrd. This routine belongs to the oneapi::mkl::lapacknamespace.

Syntax

void unmtr(cl::sycl::queue &queue, mkl::side side, mkl::uplo uplo, mkl::transpose trans, std::int64_t m, std::int64_t n, cl::sycl::buffer<T> &a, std::int64_t lda, cl::sycl::buffer<T> &tau, cl::sycl::buffer<T> &c, std::int64_t ldc, cl::sycl::buffer<T> &scratchpad, std::int64_t scratchpad_size)

unmtr supports the following precisions and devices:

T

Devices supported

std::complex<float>

Host and CPU

std::complex<double>

Host and CPU

Description

The routine multiplies a complex matrix C by Q or QH, where Q is the unitary matrix Q formed by hetrd when reducing a complex Hermitian matrix A to tridiagonal form: A = Q*T*QH. Use this routine after a call to hetrd.

Depending on the parameters left_right and trans, the routine can form one of the matrix products Q*C, QH*C, C*Q, or C*QH (overwriting the result on C).

Input Parameters

In the descriptions below, r denotes the order of Q:

r = m

if side = side::left

r = n

if side = side::right

queue

Device queue where calculations will be performed.

side

Must be either side::left or side::right.

If side = side::left, Q or QT is applied to C from the left.

If side = side::right, Q or QT is applied to C from the right.

uplo

Must be either uplo::upper or uplo::lower. Uses the same uplo as supplied to hetrd (USM Version).

trans

Must be either transpose::nontrans or transpose::trans.

If trans = transpose::nontrans, the routine multiplies C by Q.

If trans = transpose::trans, the routine multiplies C by QT.

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 hetrd (USM Version).

lda

The leading dimension of a(max(1, r) lda).

tau

Buffer holding tau returned by hetrd (USM Version). The dimension of tau must be at least max(1, r-1).

c

Buffer holding the matrix C. The second dimension of c must be at least max(1, n).

ldc

The leading dimension of c(max(1, n) ldc).

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 unmtr_scratchpad_size function.

Output Parameters

c

Overwritten by the product Q*C, QT*C, C*Q, or C*QT (as specified by side and trans).

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 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.