Visible to Intel only — GUID: GUID-8D7FB149-8762-4FCA-8DEA-A7D6C46D41B9
Visible to Intel only — GUID: GUID-8D7FB149-8762-4FCA-8DEA-A7D6C46D41B9
potrf
Computes the Cholesky factorization of a symmetric (Hermitian) positive-definite matrix.This routine belongs to the oneapi::mkl::lapack namespace.
Description
The routine forms the Cholesky factorization of a symmetric positive-definite or, for complex data, Hermitian positive-definite matrix A:
A = UT*U for real data, A = UH*U for complex data |
if uplo=mkl::uplo::upper |
A = L*LT for real data, A = L*LH for complex data |
if uplo=mkl::uplo::lower |
where L is a lower triangular matrix and U is upper triangular.
API
Syntax
namespace oneapi::mkl::lapack { void potrf(sycl::queue &queue, mkl::uplo uplo, std::int64_t n, sycl::buffer<T> &a, std::int64_t lda, sycl::buffer<T> &scratchpad, std::int64_t scratchpad_size) }
potrf supports the following precisions and devices:
T |
Devices supported |
---|---|
float |
CPU and GPU |
double |
CPU and GPU |
std::complex<float> |
CPU and GPU |
std::complex<double> |
CPU and GPU |
Input Parameters
- queue
-
Device queue where calculations will be performed.
- uplo
-
Indicates whether the upper or lower triangular part of A is stored and how A is factored:
If uplo=mkl::uplo::upper, the array a stores the upper triangular part of the matrix A, and the strictly lower triangular part of the matrix is not referenced.
If uplo=mkl::uplo::lower, the array a stores the lower triangular part of the matrix A, and the strictly upper triangular part of the matrix is not referenced.
- n
-
Specifies the order of the matrix A (0 ≤ n).
- a
-
Buffer holding input matrix A. The array holding input matrix a contains either the upper or the lower triangular part of the matrix A (see uplo). The second dimension of a must be at least max(1, n).
- lda
-
The leading dimension of a.
- 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 potrf_scratchpad_size function.
Output Parameters
- a
-
The buffer a is overwritten by the Cholesky factor U or L, as specified by uplo.
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 = i, and detail() returns 0, the leading minor of order i (and therefore the matrix A itself) is not positive-definite, and the factorization could not be completed. This may indicate an error in forming the matrix A. 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. |
Known Limitations
GPU support is for only real precisions.
GPU support for this function does not include error reporting through the info parameter.