Documentation

This is machine translation

Translated by Microsoft
Mouse over text to see original. Click the button below to return to the English verison of the page.

symbfact

Symbolic factorization analysis

Syntax

count = symbfact(A)
count = symbfact(A,'sym')
count = symbfact(A,'col')
count = symbfact(A,'row')
count = symbfact(A,'lo')
[count,h,parent,post,R] = symbfact(...)
[count,h,parent,post,L] = symbfact(A,type,'lower')

Description

count = symbfact(A) returns the vector of row counts of R=chol(A). symbfact should be much faster than chol(A).

count = symbfact(A,'sym') is the same as count = symbfact(A).

count = symbfact(A,'col') returns row counts of R=chol(A'*A) (without forming it explicitly).

count = symbfact(A,'row') returns row counts of R=chol(A*A').

count = symbfact(A,'lo') is the same as count = symbfact(A) and uses tril(A).

[count,h,parent,post,R] = symbfact(...) has several optional return values.

The flop count for a subsequent Cholesky factorization is sum(count.^2)

Return ValueDescription
h

Height of the elimination tree

parent

The elimination tree itself

post

Postordering of the elimination tree

R

0-1 matrix having the structure of chol(A) for the symmetric case, chol(A'*A) for the 'col' case, or chol(A*A') for the 'row' case.

symbfact(A) and symbfact(A,'sym') use the upper triangular part of A (triu(A)) and assume the lower triangular part is the transpose of the upper triangular part. symbfact(A,'lo') uses tril(A) instead.

[count,h,parent,post,L] = symbfact(A,type,'lower') where type is one of 'sym','col', 'row', or'lo' returns a lower triangular symbolic factor L=R'. This form is quicker and requires less memory.

See Also

| |

Introduced before R2006a

Was this topic helpful?