MATLAB Function Reference Volume 1: A - E - Bad Request

2dmperm
Purpose Dulmage-Mendelsohn decomposition
Syntax p = dmperm(A)
[p,q,r] = dmperm(A)
[p,q,r,s] = dmperm(A)
dmperm
Description If A is a reducible matrix, the linear system Ax =
b can be solved by permuting
A to a block upper triangular form, with irreducible diagonal blocks, and then
performing block backsubstitution. Only the diagonal blocks of the permuted
matrix need to be factored, saving fill and arithmetic in the blocks above the
diagonal.
See Also sprank
p = dmperm(A) returns a row permutation p so that if A has full column rank,
A(p,:) is square with nonzero diagonal. This is also called a maximum
matching.
[p,q,r] = dmperm(A) where A is a square matrix, finds a row permutation p
and a column permutation q so that A(p,q) is in block upper triangular form.
The third output argument r is an integer vector describing the boundaries of
the blocks: The kth block of A(p,q) has indices r(k):r(k+1)-1.
[p,q,r,s] = dmperm(A), where A is not square, finds permutations p and q
and index vectors r and s so that A(p,q) is block upper triangular. The blocks
have indices (r(i):r(i+1)-1, s(i):s(i+1)-1).
If A is not square, the first block may have more columns and the last block may
have more rows. All other blocks are square. dmperm permutes nonzeros to the
diagonals of square blocks, but does not do this for non-square blocks.
In graph theoretic terms, the diagonal blocks correspond to strong Hall
components of the adjacency graph of A.
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