Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

ID 766686
Date 11/07/2023
Public

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?tftri

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

Syntax

call stftri( transr, uplo, diag, n, a, info )

call dtftri( transr, uplo, diag, n, a, info )

call ctftri( transr, uplo, diag, n, a, info )

call ztftri( transr, uplo, diag, n, a, info )

Include Files

  • mkl.fi, lapack.f90

Description

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

transr

CHARACTER*1. 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

CHARACTER*1. 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

CHARACTER*1. 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

INTEGER. The order of the matrix A; n 0.

a

REAL for stftri

DOUBLE PRECISION for dtftri

COMPLEX for ctftri

DOUBLE COMPLEX for ztftri.

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.

info

INTEGER. If info=0, the execution is successful.

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

If info = i, A(i,i) is exactly zero. The triangular matrix is singular and its inverse cannot be computed.