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 = U T *U for real data, A = U H *U for complex data | if uplo= mkl::uplo::upper |
A = L *L T for real data, A = L *L H 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(cl::sycl::queue &queue,
mkl::uplo uplo,
std::int64_t n,
cl::sycl::buffer<T> &a,
std::int64_t lda,
cl::sycl::buffer<T> &scratchpad,
std::int64_t scratchpad_size)
}
potrf
supports the following precisions and devices:T | Devices supported |
---|---|
float | Host, CPU, and GPU |
double | Host, CPU, and GPU |
std::complex<float> | Host, CPU, and GPU |
std::complex<double> | Host, CPU, and GPU |
Input Parameters
- queue
- Device queue where calculations will be performed.
- uplo
- Indicates whether the upper or lower triangular part ofAis stored and howAis factored:If uplo=mkl::uplo::upper, the arrayastores the upper triangular part of the matrixA, and the strictly lower triangular part of the matrix is not referenced.If uplo=mkl::uplo::lower, the arrayastores the lower triangular part of the matrixA, and the strictly upper triangular part of the matrix is not referenced.
- n
- Specifies the order of the matrixA(0≤n).
- a
- Buffer holding input matrixA. The array holding input matrix a contains either the upper or the lower triangular part of the matrixA(see uplo). The second dimension of a must be at leastmax(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 typeT. 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 factorUorL, 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 theinfoparameter.