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Adding initial lagrangian interpolation.

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This commit is contained in:
Patrick Shriwise 2022-08-06 06:48:47 -05:00
parent 4ba9acd459
commit 48a9ac9a2c
1 changed files with 25 additions and 0 deletions
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25
include/openmc/interpolate.h
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@ -60,6 +60,31 @@ inline double interpolate(const std::vector<double>& xs,
return interpolate(xs, ys, idx, x, i);
}
inline double interpolate_lagrangian(
const std::vector<double>& xs, const std::vector<double>& ys, double x)
{
int idx = lower_bound_index(xs.begin(), xs.end(), x);
std::vector<double> coeffs;
int order = 3;
for (int i = 0; i < order + 1; i++) {
double numerator {1.0};
double denominator {1.0};
for (int j = 0; j < order; j++) {
if (i == j)
continue;
numerator *= (x - xs[idx + j]);
denominator *= (xs[idx + i] - xs[idx + j]);
}
coeffs.push_back(numerator / denominator);
}
return std::inner_product(
coeffs.begin(), coeffs.end(), ys.begin() + idx, 0.0);
}
} // namespace openmc
#endif