package edu.emory.mathcs.csparsej.tdouble;
import edu.emory.mathcs.csparsej.tdouble.Dcs_common.Dcs;
/**
* Permute a sparse matrix.
*
* @author Piotr Wendykier (piotr.wendykier@gmail.com)
*
*/
public class Dcs_permute {
/**
* Permutes a sparse matrix, C = PAQ.
*
* @param A
* m-by-n, column-compressed matrix
* @param pinv
* a permutation vector of length m
* @param q
* a permutation vector of length n
* @param values
* allocate pattern only if false, values and pattern otherwise
* @return C = PAQ, null on error
*/
public static Dcs cs_permute(Dcs A, int[] pinv, int[] q, boolean values) {
int t, j, k, nz = 0, m, n, Ap[], Ai[], Cp[], Ci[];
double Cx[], Ax[];
Dcs C;
if (!Dcs_util.CS_CSC(A))
return (null); /* check inputs */
m = A.m;
n = A.n;
Ap = A.p;
Ai = A.i;
Ax = A.x;
C = Dcs_util.cs_spalloc(m, n, Ap[n], values && Ax != null, false); /* alloc result */
Cp = C.p;
Ci = C.i;
Cx = C.x;
for (k = 0; k < n; k++) {
Cp[k] = nz; /* column k of C is column q[k] of A */
j = q != null ? (q[k]) : k;
for (t = Ap[j]; t < Ap[j + 1]; t++) {
if (Cx != null)
Cx[nz] = Ax[t]; /* row i of A is row pinv[i] of C */
Ci[nz++] = pinv != null ? (pinv[Ai[t]]) : Ai[t];
}
}
Cp[n] = nz; /* finalize the last column of C */
return C;
}
}