LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
subroutine  dtptri (UPLO, DIAG, N, AP, INFO) 
DTPTRI 
subroutine dtptri  (  character  UPLO, 
character  DIAG,  
integer  N,  
double precision, dimension( * )  AP,  
integer  INFO  
) 
DTPTRI
Download DTPTRI + dependencies [TGZ] [ZIP] [TXT]DTPTRI computes the inverse of a real upper or lower triangular matrix A stored in packed format.
[in]  UPLO  UPLO is CHARACTER*1 = 'U': A is upper triangular; = 'L': A is lower triangular. 
[in]  DIAG  DIAG is CHARACTER*1 = 'N': A is nonunit triangular; = 'U': A is unit triangular. 
[in]  N  N is INTEGER The order of the matrix A. N >= 0. 
[in,out]  AP  AP is DOUBLE PRECISION array, dimension (N*(N+1)/2) On entry, the upper or lower triangular matrix A, stored columnwise in a linear array. The jth column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j1)*((2*nj)/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. 
[out]  INFO  INFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith 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. 
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+I1) = A(I,J) AP(JC+IJ) = 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 dtptri.f.