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// Gmsh - Copyright (C) 1997-2020 C. Geuzaine, J.-F. Remacle
//
// See the LICENSE.txt file for license information. Please report all
// issues on https://gitlab.onelab.info/gmsh/gmsh/issues.
#include "approximationError.h"
#include "MElement.h"
double approximationError(simpleFunction<double> &f, MElement *element)
{
std::vector<double> VALS(element->getNumVertices());
for(std::size_t i = 0; i < element->getNumVertices(); i++) {
MVertex *v = element->getVertex(i);
VALS[i] = f(v->x(), v->y(), v->z());
}
int npts;
IntPt *pts;
element->getIntegrationPoints(2 * element->getPolynomialOrder() + 2, &npts,
&pts);
double errSqr = 0.0;
for(int k = 0; k < npts; k++) {
const double u = pts[k].pt[0];
const double v = pts[k].pt[1];
const double w = pts[k].pt[2];
SPoint3 p;
element->pnt(u, v, w, p);
const double Jac = element->getJacobianDeterminant(u, v, w);
const double C = element->interpolate(&VALS[0], u, v, w);
const double F = f(p.x(), p.y(), p.z());
errSqr += pts[k].weight * Jac * std::pow(C - F, 2);
}
return std::sqrt(errSqr);
}
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