Developer Reference for Intel® oneAPI Math Kernel Library for C
?sytri2
Computes the inverse of a symmetric indefinite matrix through setting the leading dimension of the workspace allocating memory and calling ?sytri2x .
Syntax
lapack_intLAPACKE_ssytri2 ( intmatrix_layout , charuplo , lapack_intn , float*a , lapack_intlda , constlapack_int*ipiv );
lapack_intLAPACKE_dsytri2 ( intmatrix_layout , charuplo , lapack_intn , double*a , lapack_intlda , constlapack_int*ipiv );
lapack_intLAPACKE_csytri2 ( intmatrix_layout , charuplo , lapack_intn , lapack_complex_float*a , lapack_intlda , constlapack_int*ipiv );
lapack_intLAPACKE_zsytri2 ( intmatrix_layout , charuplo , lapack_intn , lapack_complex_double*a , lapack_intlda , constlapack_int*ipiv );
Include Files
mkl.h
Description
The routine computes the inverse inv(A) of a symmetric indefinite matrix A using the factorization A = U*D*U^{T} or A = L*D*L^{T} computed by ?sytrf .
The ?sytri2 routine sets the leading dimension of the workspace allocates a temporary buffer before calling ?sytri2x that actually computes the inverse.
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*U^{T} .
If uplo = 'L' , the array a stores the factorization A = L*D*L^{T} .
n
The order of the matrix A ; n≥ 0 .
a , work
Array a (size max(1, lda * n )) contains the block diagonal matrix D and the multipliers used to obtain the factor U or L as returned by ?sytrf .
lda
The leading dimension of a ; lda≥ max(1, n) .
ipiv
Array, size at least max(1, n) .
Details of the interchanges and the block structure of D as returned by ?sytrf .
lwork
The dimension of the work array.
lwork≥ (n+nb+1)*(nb+3)
where
nb is the block size parameter as returned by sytrf .
If lwork = -1 , then a workspace query is assumed; the routine only calculates the optimal size of the work array, returns this value as the first entry of the work array, and no error message related to lwork is issued by xerbla .
Output Parameters
a
If info = 0 , the symmetric inverse of the original matrix.
If uplo = 'U' , the upper triangular part of the inverse is formed and the part of A below the diagonal is not referenced.
If uplo = '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 , the i- th parameter had an illegal value.
If info = i , D ( i , i ) = 0; D is singular and its inversion could not be computed.
LAPACK 95 Interface Notes
There exist FORTRAN 77 and FORTRAN 95 interfaces for this routine. See the Intel® oneMKL Fortran Developer Reference for details.