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/* Ergo, version 3.8.2, a program for linear scaling electronic structure
* calculations.
* Copyright (C) 2023 Elias Rudberg, Emanuel H. Rubensson, Pawel Salek,
* and Anastasia Kruchinina.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Primary academic reference:
* Ergo: An open-source program for linear-scaling electronic structure
* calculations,
* Elias Rudberg, Emanuel H. Rubensson, Pawel Salek, and Anastasia
* Kruchinina,
* SoftwareX 7, 107 (2018),
* <http://dx.doi.org/10.1016/j.softx.2018.03.005>
*
* For further information about Ergo, see <http://www.ergoscf.org>.
*/
/** @file simple_sparse_mat.cc
@brief Simple sparse matrix implementation.
@author: Elias Rudberg <em>responsible</em>
*/
#include "simple_sparse_mat.h"
#include <cmath>
#include <stdexcept>
#include <cstdlib>
static int
compare_i_j_val_structs(const void* p1, const void* p2)
{
i_j_val_struct* struct_1 = (i_j_val_struct*)p1;
i_j_val_struct* struct_2 = (i_j_val_struct*)p2;
const int returnValue1 = -1;
const int returnValue2 = 1;
if(struct_1->i < struct_2->i)
return returnValue1;
if(struct_1->i > struct_2->i)
return returnValue2;
if(struct_1->j < struct_2->j)
return returnValue1;
if(struct_1->j > struct_2->j)
return returnValue2;
return 0;
}
int spmat_sort_elements(i_j_val_struct* A, int nnzA) {
qsort(A, nnzA, sizeof(i_j_val_struct), compare_i_j_val_structs);
// Verify sort
for(int k = 0; k < nnzA-1; k++) {
if(A[k+1].i < A[k].i)
throw std::runtime_error("ERROR in spmat_sort_elements: list not properly sorted.");
}
for(int k = 0; k < nnzA; k++) {
// Check how many elements have the same i-value
int kk = k;
while(kk < nnzA) {
if(A[kk].i != A[k].i)
break;
kk++;
}
// Now kk is the index of the first element found that does not have the same i-value (or kk==nnzA)
A[k].same_i_count = kk - k;
}
return 0;
}
int spmat_multiply_matrices(const i_j_val_struct* A, int nnzA, const i_j_val_struct* B, int nnzB, i_j_val_struct* C, int M, int N) {
i_j_val_struct* Cbuf = new i_j_val_struct[M*N];
int counters[M];
for(int i = 0; i < M; i++)
counters[i] = 0;
for(int idxA = 0; idxA < nnzA; idxA++)
for(int idxB = 0; idxB < nnzB; idxB++) {
if(A[idxA].j != B[idxB].i)
continue;
int i = A[idxA].i;
int j = B[idxB].j;
// OK, we have a contribution to C_i_j
ergo_real contribValue = A[idxA].value * B[idxB].value;
if(i < 0 || i >= M || j < 0 || j >= N)
throw std::runtime_error("ERROR in multiply_matrices_sp: i, j out of bounds.");
// Check if there is already an entry for this index pair.
bool found = false;
for(int k = 0; k < counters[i]; k++) {
i_j_val_struct & p = Cbuf[i*N+k];
if(p.i == i && p.j == j) {
p.value += contribValue;
found = true;
break;
}
}
if(found == false) {
if(counters[i] >= N)
throw std::runtime_error("ERROR in multiply_matrices_sp: (counters[i] >= N)");
i_j_val_struct & p = Cbuf[i*N+counters[i]];
counters[i]++;
p.i = i;
p.j = j;
p.same_i_count = 1;
p.value = contribValue;
}
}
// Now create final result in C
int count = 0;
for(int i = 0; i < M; i++)
for(int k = 0; k < counters[i]; k++) {
C[count] = Cbuf[i*N+k];
count++;
}
delete [] Cbuf;
return count;
}
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