|
NAG[f07gjc] NAG[nag_dpptri] - Inverse of real symmetric positive-definite matrix, matrix already factorized by f07gdc (nag_dpptrf), packed storage
|
|
Calling Sequence
f07gjc(uplo, n, ap, 'fail'=fail)
nag_dpptri(. . .)
Parameters
|
uplo - String;
|
|
|
Constraint: "Nag_Upper" or "Nag_Lower". .
|
|
|
n - integer;
|
|
|
On entry: , the order of the matrix .
|
|
Constraint: . .
|
|
|
ap - Vector(1..dim, datatype=float[8]);
|
|
|
Note: the dimension, dim, of the array ap must be at least .
|
|
|
'fail'=fail - table; (optional)
|
|
|
The NAG error argument, see the documentation for NagError.
|
|
|
|
Description
|
|
|
Purpose
|
|
nag_dpptri (f07gjc) computes the inverse of a real symmetric positive-definite matrix , where has been factorized by f07gdc (nag_dpptrf), using packed storage.
|
|
Error Indicators and Warnings
|
|
"NE_BAD_PARAM"
On entry, argument had an illegal value.
"NE_INT"
On entry, . Constraint: .
"NE_INTERNAL_ERROR"
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please consult NAG for assistance.
"NE_SINGULAR"
Element of the diagonal of the Cholesky factor is zero. The Cholesky factor is singular, and the inverse of cannot be computed.
|
|
Further Comments
|
|
The total number of floating-point operations is approximately .
The complex analogue of this function is f07gwc (nag_zpptri).
|
|
|
Examples
|
|
>
|
uplo := "Nag_Lower":
n := 4:
ap := Vector([2.039607805437114, -1.529705854077835, 1.640121946685673, 0.2745625891934577, -0.2499814119483738, 0.7887488055748053, -0.049029033784546, 0.6737303907389099, 0.6616575633742564, 0.5346894269298686], datatype=float[8], order='C_order'):
NAG:-f07gjc(uplo, n, ap):
|
|
|