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int | genmmd_ (int *, int *, int *, int *, int *, int *, int *, int *, int *, int *, int *, int *) |
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void | get_colamd (const int m, const int n, const int nnz, int *colptr, int *rowind, int *perm_c) |
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void | getata (const int m, const int n, const int nz, int *colptr, int *rowind, int *atanz, int **ata_colptr, int **ata_rowind) |
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void | at_plus_a (const int n, const int nz, int *colptr, int *rowind, int *bnz, int **b_colptr, int **b_rowind) |
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void | get_perm_c (int ispec, SuperMatrix *A, int *perm_c) |
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– SuperLU routine (version 3.1) –
Univ. of California Berkeley, Xerox Palo Alto Research Center,
and Lawrence Berkeley National Lab.
August 1, 2008
void get_perm_c |
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int |
ispec, |
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SuperMatrix * |
A, |
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int * |
perm_c |
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) |
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Purpose
GET_PERM_C obtains a permutation matrix Pc, by applying the multiple
minimum degree ordering code by Joseph Liu to matrix A'*A or A+A'.
or using approximate minimum degree column ordering by Davis et. al.
The LU factorization of A*Pc tends to have less fill than the LU
factorization of A.
Arguments
ispec (input) int
Specifies the type of column ordering to reduce fill:
= 1: minimum degree on the structure of A^T * A
= 2: minimum degree on the structure of A^T + A
= 3: approximate minimum degree for unsymmetric matrices
If ispec == 0, the natural ordering (i.e., Pc = I) is returned.
A (input) SuperMatrix*
Matrix A in A*X=B, of dimension (A->nrow, A->ncol). The number
of the linear equations is A->nrow. Currently, the type of A
can be: Stype = NC; Dtype = _D; Mtype = GE. In the future,
more general A can be handled.
perm_c (output) int*
Column permutation vector of size A->ncol, which defines the
permutation matrix Pc; perm_c[i] = j means column i of A is
in position j in A*Pc.
void getata |
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const int |
m, |
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const int |
n, |
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const int |
nz, |
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int * |
colptr, |
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int * |
rowind, |
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int * |
atanz, |
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int ** |
ata_colptr, |
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int ** |
ata_rowind |
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) |
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Purpose
Form the structure of A'*A. A is an m-by-n matrix in column oriented
format represented by (colptr, rowind). The output A'*A is in column
oriented format (symmetrically, also row oriented), represented by
(ata_colptr, ata_rowind).
This routine is modified from GETATA routine by Tim Davis.
The complexity of this algorithm is: SUM_{i=1,m} r(i)^2,
i.e., the sum of the square of the row counts.
Questions
o Do I need to withhold the dense rows?
o How do I know the number of nonzeros in A'*A?