ctptri-f(3)

ctptri.f –

Synopsis

Functions/Subroutines

subroutine ctptri (UPLO, DIAG, N, AP, INFO)
CTPTRI

Function/Subroutine Documentation

subroutine ctptri (characterUPLO, characterDIAG, integerN, complex, dimension( * )AP, integerINFO)

CTPTRI

Purpose:

 CTPTRI computes the inverse of a complex upper or lower triangular
 matrix A stored in packed format.

 

Parameters:

UPLO

 UPLO is CHARACTER*1
 = 'U': A is upper triangular;
 = 'L': A is lower triangular.

DIAG

 DIAG is CHARACTER*1
 = 'N': A is non-unit triangular;
 = 'U': A is unit triangular.

N

 N is INTEGER
 The order of the matrix A. N >= 0.

AP

 AP is COMPLEX array, dimension (N*(N+1)/2)
 On entry, the upper or lower triangular matrix A, stored
 columnwise in a linear array. The j-th column of A is stored
 in the array AP as follows:
 if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
 if UPLO = 'L', AP(i + (j-1)*((2*n-j)/2) = A(i,j) for j<=i<=n.
 See below for further details.
 On exit, the (triangular) inverse of the original matrix, in
 the same packed storage format.

INFO

 INFO is INTEGER
 = 0: successful exit
 < 0: if INFO = -i, the i-th argument had an illegal value
 > 0: if INFO = i, A(i,i) is exactly zero. The triangular
 matrix is singular and its inverse can not be computed.

 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Further Details:

 A triangular matrix A can be transferred to packed storage using one
 of the following program segments:
 UPLO = 'U': UPLO = 'L':
 JC = 1 JC = 1
 DO 2 J = 1, N DO 2 J = 1, N
 DO 1 I = 1, J DO 1 I = J, N
 AP(JC+I-1) = A(I,J) AP(JC+I-J) = A(I,J)
 1 CONTINUE 1 CONTINUE
 JC = JC + J JC = JC + N - J + 1
 2 CONTINUE 2 CONTINUE

 

Definition at line 118 of file ctptri.f.

Author

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