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/* Ergo, version 3.5, a program for linear scaling electronic structure
* calculations.
* Copyright (C) 2016 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:
* KohnâSham Density Functional Theory Electronic Structure Calculations
* with Linearly Scaling Computational Time and Memory Usage,
* Elias Rudberg, Emanuel H. Rubensson, and Pawel Salek,
* J. Chem. Theory Comput. 7, 340 (2011),
* <http://dx.doi.org/10.1021/ct100611z>
*
* For further information about Ergo, see <http://www.ergoscf.org>.
*/
/** @file explicit_integral_test.cc Tests the explicit computation of
2-electron integrals by moving basis functions by small distances
and verifying that the computed 2-el integrals vary smoothly. */
#include <stdio.h>
#include <unistd.h>
#include <memory>
#include <limits>
#include <vector>
#include "integrals_2el_explicit.h"
int try_integral_diffs(const IntegralInfo & integralInfo, ergo_real h) {
Molecule m;
int nx = 2;
int ny = 1;
int nz = 1;
const ergo_real space = 8.8;
int atomCount = 0;
for(int ix = 0; ix < nx; ix++)
for(int iy = 0; iy < ny; iy++)
for(int iz = 0; iz < nz; iz++)
{
ergo_real x = ix*space + 0.4*std::cos((ix+iy+iz)*0.2+0.0)*space;
ergo_real y = iy*space + 0.4*std::cos((ix+iy+iz)*0.2+0.3)*space;
ergo_real z = iz*space + 0.4*std::cos((ix+iy+iz)*0.2+0.6)*space;
/* Use a mix of charges: H, C, Zn.
It is good to have some Zn there so we check also usage
of basis functions of f type. */
int charge = 1;
if(atomCount%3 == 0)
charge = 6;
// if(atomCount%9 == 0)
// charge = 30;
m.addAtom(charge, x, y, z);
atomCount++;
}
ergo_real moleculeBaseCoord = m.getAtom(0).coords[0];
ergo_real machine_epsilon = std::numeric_limits<ergo_real>::epsilon();
// OK, now we have a molecule. Now do a loop where we move one atom
// by a small distance and save resulting 2-el integrals for each
// case.
const int noOfCases = 55;
std::vector< std::vector< std::vector< std::vector< std::vector<ergo_real> > > > > integralList(noOfCases);
int n = 0; // Will be set later.
for(int caseIdx = 0; caseIdx < noOfCases; caseIdx++) {
// Move first atom by small distance in x direction.
Atom atom = m.getAtom(0);
atom.coords[0] = moleculeBaseCoord + caseIdx * h;
m.replaceAtom(0, atom);
// New scope here so that the BasisInfoStruct pointer is freed each time.
{
BasisInfoStruct bis;
if(bis.addBasisfuncsForMolecule(m, ERGO_SPREFIX "/basis/3-21G",
0, NULL, integralInfo, 0, 0, 0) != 0) {
printf("bis.addBasisfuncsForMolecule failed.\n");
return -1;
}
// OK, now we have a basis set for the current version of the
// molecule. Now compute integrals.
n = bis.noOfBasisFuncs;
integralList[caseIdx].resize(n);
for(int i = 0; i < n; i++) {
integralList[caseIdx][i].resize(n);
for(int j = i; j < n; j++) {
integralList[caseIdx][i][j].resize(n);
for(int k = 0; k < n; k++) {
integralList[caseIdx][i][j][k].resize(n);
for(int l = k; l < n; l++) {
integralList[caseIdx][i][j][k][l] = do_2e_integral(i, k, l, j, bis, integralInfo);
}
}
}
}
} // End of scope for temporary BasisInfoStruct
} // END FOR caseIdx
// OK, now we have integrals computed for all cases. Now check if
// each integral value varies smoothly.
int count = 0;
for(int i = 0; i < n; i++)
for(int j = i; j < n; j++)
for(int k = 0; k < n; k++)
for(int l = k; l < n; l++) {
// Now we are interested in the integral (ij|kl). First
// check if this integral values seems to be approximately
// linearly dependent on the modufied atomic coordinate.
ergo_real totDiff = integralList[noOfCases-1][i][j][k][l] - integralList[0][i][j][k][l];
ergo_real halfDiff = integralList[noOfCases/2][i][j][k][l] - integralList[0][i][j][k][l];
if(halfDiff != 0 && std::fabs(totDiff) > machine_epsilon) {
ergo_real kvot = totDiff / halfDiff;
// Now if kvot is approximately 2 we think this integral behaves linearly.
if(kvot > 1.95 && kvot < 2.05) {
count++;
for(int caseIdx = 1; caseIdx < noOfCases; caseIdx++) {
ergo_real diff = integralList[caseIdx][i][j][k][l] - integralList[caseIdx-1][i][j][k][l];
ergo_real expectedDiff = totDiff / (noOfCases-1);
if(diff/expectedDiff < 0.9 || diff/expectedDiff > 1.1) {
printf("Error for integral i j k l : %d %d %d %d, expectedDiff = %9.5g, diff = %9.5g\n",
i, j, k, l, (double)expectedDiff, (double)diff);
return -1;
} // END IF
} // END FOR caseIdx
} // END IF
} // END IF (halfDiff != 0)
} // END FOR i j k l
unlink("ergoscf.out");
printf("try_integral_diffs finished OK, count = %d.\n", count);
if(count == 0)
exit(0);
return 0;
}
int main(int argc, char *argv[]) {
IntegralInfo integralInfo(true);
integralInfo.init();
ergo_real machine_epsilon = std::numeric_limits<ergo_real>::epsilon();
ergo_real h = 10000*machine_epsilon;
printf("machine_epsilon = %9.5g, using h = %9.5g\n", (double)machine_epsilon, (double)h);
if(try_integral_diffs(integralInfo, h) != 0)
return -1;
return 0;
}
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