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// CXSparse/Source/cs_add: sparse matrix addition
// CXSparse, Copyright (c) 2006-2022, Timothy A. Davis. All Rights Reserved.
// SPDX-License-Identifier: LGPL-2.1+
#include "cs.h"
/* C = alpha*A + beta*B */
cs *cs_add (const cs *A, const cs *B, CS_ENTRY alpha, CS_ENTRY beta)
{
CS_INT p, j, nz = 0, anz, *Cp, *Ci, *Bp, m, n, bnz, *w, values ;
CS_ENTRY *x, *Bx, *Cx ;
cs *C ;
if (!CS_CSC (A) || !CS_CSC (B)) return (NULL) ; /* check inputs */
if (A->m != B->m || A->n != B->n) return (NULL) ;
m = A->m ; anz = A->p [A->n] ;
n = B->n ; Bp = B->p ; Bx = B->x ; bnz = Bp [n] ;
w = cs_calloc (m, sizeof (CS_INT)) ; /* get workspace */
values = (A->x != NULL) && (Bx != NULL) ;
x = values ? cs_malloc (m, sizeof (CS_ENTRY)) : NULL ; /* get workspace */
C = cs_spalloc (m, n, anz + bnz, values, 0) ; /* allocate result*/
if (!C || !w || (values && !x)) return (cs_done (C, w, x, 0)) ;
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 = cs_scatter (A, j, alpha, w, x, j+1, C, nz) ; /* alpha*A(:,j)*/
nz = 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 */
cs_sprealloc (C, 0) ; /* remove extra space from C */
return (cs_done (C, w, x, 1)) ; /* success; free workspace, return C */
}
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