?tftri

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 4/28/2026

Version

Public

?tftri

Computes the inverse of a triangular matrix stored in the Rectangular Full Packed (RFP) format.

Syntax

lapack_intLAPACKE_stftri ( intmatrix_layout , chartransr , charuplo , chardiag , lapack_intn , float*a );

lapack_intLAPACKE_dtftri ( intmatrix_layout , chartransr , charuplo , chardiag , lapack_intn , double*a );

lapack_intLAPACKE_ctftri ( intmatrix_layout , chartransr , charuplo , chardiag , lapack_intn , lapack_complex_float*a );

lapack_intLAPACKE_ztftri ( intmatrix_layout , chartransr , charuplo , chardiag , lapack_intn , lapack_complex_double*a );

Include Files

mkl.h

Description

stftri dtftri ctftri ztftri

Computes the inverse of a triangular matrix A stored in the Rectangular Full Packed (RFP) format. For the description of the RFP format, see Matrix Storage Schemes .

This is the block version of the algorithm, calling Level 3 BLAS.

Input Parameters

matrix_layout

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

transr

Must be ‘N’ , ‘T’ (for real data) or ‘C’ (for complex data).

If transr = ‘N’ , the Normal transr of RFP A is stored.

If transr = ‘T’ , the Transpose transr of RFP A is stored.

If transr = ‘C’ , the Conjugate-Transpose transr of RFP A is stored.

uplo

Must be ‘U’ or ‘L’ .

Indicates whether the upper or lower triangular part of RFP A is stored:

If uplo = ‘U’ , the array a stores the upper triangular part of the matrix A .

If uplo = ‘L’ , the array a stores the lower triangular part of the matrix A .

diag

Must be ‘N’ or ‘U’ .

If diag = 'N' , then A is not a unit triangular matrix.

If diag = 'U' , A is unit triangular: diagonal elements of A are assumed to be 1 and not referenced in the array a .

n

The order of the matrix A ; n ≥ 0.

a

Array, size max(1, n *( n + 1)/2). The array a contains the matrix A in the RFP format.

Output Parameters

a

The (triangular) inverse of the original matrix in the same storage format.

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 , A_{i, i} is exactly zero. The triangular matrix is singular and its inverse cannot be computed.

NOTE:

Matrix Storage Schemes

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Developer Reference for Intel® oneAPI Math Kernel Library for C

?tftri

Syntax

Include Files

Description

Input Parameters

Output Parameters

Return Values