The elements of A^-1 at the positions of the factor's pattern. It is what PEV and accuracy
read, and the only part of the inverse one can afford: the full inverse of the coefficient
matrix is dense.
Usage
selected_inverse(a, block = 0L)
Arguments
- a
list i, j, x, n with the triplets
- block
0 detects the dense tail and uses the closed form; 1 forces the pure
recurrence, which exists so the tests can compare the two paths.
Value
a list i, j, x, n with the computed elements of the inverse in triplets, on
the pattern of the factor. A position outside that pattern is absent, which is not
the same as being zero.
Details
A position OUTSIDE the pattern is not zero, it is unknown. The result only carries the
ones that were computed.
References
Takahashi, K., Fagan, J. & Chin, M.-S. (1973). Formation of a sparse
bus impedance matrix and its application to short circuit study. Proceedings of
the 8th PICA Conference, 63-69.
