package edu.emory.mathcs.csparsej.tdouble;
import edu.emory.mathcs.csparsej.tdouble.Dcs_common.Dcs;
/**
* Add sparse matrices.
*
* @author Piotr Wendykier (piotr.wendykier@gmail.com)
*
*/
public class Dcs_add {
/**
* C = alpha*A + beta*B
*
* @param A
* column-compressed matrix
* @param B
* column-compressed matrix
* @param alpha
* scalar alpha
* @param beta
* scalar beta
* @return C=alpha*A + beta*B, null on error
*/
public static Dcs cs_add(Dcs A, Dcs B, double alpha, double beta) {
int p, j, nz = 0, anz;
int Cp[], Ci[], Bp[], m, n, bnz, w[];
double x[], Bx[], Cx[];
boolean values;
Dcs C;
if (!Dcs_util.CS_CSC(A) || !Dcs_util.CS_CSC(B))
return null; /* check inputs */
if (A.m != B.m || A.n != B.n)
return null;
m = A.m; // number of rows
anz = A.p[A.n]; // non-zero elements of matrix A
n = B.n; // number of columns
Bp = B.p;
Bx = B.x; // data elements of matrix B
bnz = Bp[n];
w = new int[m]; /* get workspace */
values = (A.x != null) && (Bx != null);
x = values ? new double[m] : null; /* get workspace */
C = Dcs_util.cs_spalloc(m, n, anz + bnz, values, false); /* allocate result*/
Cp = C.p;
Ci = C.i;
Cx = C.x;
for (j = 0; j < n; j++) {
Cp[j] = nz; /* column j of C starts here */
nz = Dcs_scatter.cs_scatter(A, j, alpha, w, x, j + 1, C, nz); /* alpha*A(:,j)*/
nz = Dcs_scatter.cs_scatter(B, j, beta, w, x, j + 1, C, nz); /* beta*B(:,j) */
if (values)
for (p = Cp[j]; p < nz; p++)
Cx[p] = x[Ci[p]];
}
Cp[n] = nz; /* finalize the last column of C */
Dcs_util.cs_sprealloc(C, 0); /* remove extra space from C */
return C; /* success; free workspace, return C */
}
}