Developer Reference for Intel® oneAPI Math Kernel Library for C

ID 766684
Date 3/22/2024
Public

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?sytri2x

Computes the inverse of a symmetric indefinite matrix after ?sytri2allocates memory.

Syntax

lapack_int LAPACKE_ssytri2x (int matrix_layout , char uplo , lapack_int n , float * a , lapack_int lda , const lapack_int * ipiv , lapack_int nb );

lapack_int LAPACKE_dsytri2x (int matrix_layout , char uplo , lapack_int n , double * a , lapack_int lda , const lapack_int * ipiv , lapack_int nb );

lapack_int LAPACKE_csytri2x (int matrix_layout , char uplo , lapack_int n , lapack_complex_float * a , lapack_int lda , const lapack_int * ipiv , lapack_int nb );

lapack_int LAPACKE_zsytri2x (int matrix_layout , char uplo , lapack_int n , lapack_complex_double * a , lapack_int lda , const lapack_int * ipiv , lapack_int nb );

Include Files

  • mkl.h

Description

The routine computes the inverse inv(A) of a symmetric indefinite matrix A using the factorization A = U*D*UT or A = L*D*LT computed by ?sytrf.

The ?sytri2x actually computes the inverse after the ?sytri2 routine allocates memory before calling ?sytri2x.

Input Parameters

matrix_layout

Specifies whether matrix storage layout is row major (LAPACK_ROW_MAJOR) or column major (LAPACK_COL_MAJOR).

uplo

Must be 'U' or 'L'.

Indicates how the input matrix A has been factored:

If uplo = 'U', the array a stores the factorization A = U*D*UT.

If uplo = 'L', the array a stores the factorization A = L*D*LT.

n

The order of the matrix A; n 0.

a

Array a (size max(1, lda*n)) contains the nb (block size) diagonal matrix D and the multipliers used to obtain the factor U or L as returned by ?sytrf. The second dimension of a must be at least max(1,n).

lda

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

ipiv

Array, size at least max(1, n).

Details of the interchanges and the nb structure of D as returned by ?sytrf.

nb

Block size.

Output Parameters

a

If info = 0, the symmetric inverse of the original matrix.

If info = 'U', the upper triangular part of the inverse is formed and the part of A below the diagonal is not referenced.

If info = 'L', the lower triangular part of the inverse is formed and the part of A above the diagonal is not referenced.

Return Values

This function returns a value info.

If info = 0, the execution is successful.

If info =-i, parameter i had an illegal value.

If info = i, Dii= 0; D is singular and its inversion could not be computed.