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aka_math.cc
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/**
* Copyright (©) 2010-2023 EPFL (Ecole Polytechnique Fédérale de Lausanne)
* Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
*
* This file is part of Akantu
*
* Akantu is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option) any
* later version.
*
* Akantu 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 Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Akantu. If not, see <http://www.gnu.org/licenses/>.
*/
/* -------------------------------------------------------------------------- */
#include "aka_math.hh"
#include "aka_array.hh"
#include "aka_iterators.hh"
/* -------------------------------------------------------------------------- */
namespace akantu {
namespace Math {
/* ---------------------------------------------------------------------- */
void compute_tangents(const Array<Real> & normals, Array<Real> & tangents) {
if (normals.empty()) {
return;
}
auto spatial_dimension = normals.getNbComponent();
auto tangent_components = spatial_dimension * (spatial_dimension - 1);
if (tangent_components == 0) {
return;
}
AKANTU_DEBUG_ASSERT(
tangent_components == tangents.getNbComponent(),
"Cannot compute the tangents, the storage array for tangents"
<< " does not have the good amount of components.");
auto nb_normals = normals.size();
tangents.resize(nb_normals);
tangents.zero();
/// compute first tangent
for (auto && data :
zip(make_view(normals, spatial_dimension),
make_view(tangents, spatial_dimension, spatial_dimension - 1))) {
const auto & normal_ = std::get<0>(data);
auto & tangent = std::get<1>(data);
if (are_float_equal(normal_.norm(), 0.)) {
tangent(0, 0) = 1.;
} else {
tangent(0) = normal(normal_);
}
}
/// compute second tangent (3D case)
if (spatial_dimension == 3) {
for (auto && data :
zip(make_view(normals, spatial_dimension),
make_view(tangents, spatial_dimension, spatial_dimension - 1))) {
const auto & normal_ = std::get<0>(data);
auto & tangent = std::get<1>(data);
tangent(1) = normal(normal_, tangent(0));
}
}
}
/* ---------------------------------------------------------------------- */
Real reduce(Array<Real> & array) {
UInt nb_values = array.size();
if (nb_values == 0) {
return 0.;
}
Int nb_values_to_sum = nb_values >> 1;
std::sort(array.begin(), array.end());
// as long as the half is not empty
while (nb_values_to_sum != 0) {
Int remaining = (nb_values - 2 * nb_values_to_sum);
if (remaining != 0U) {
array(nb_values - 2) += array(nb_values - 1);
}
// sum to consecutive values and store the sum in the first half
for (Int i = 0; i < nb_values_to_sum; ++i) {
array(i) = array(2 * i) + array(2 * i + 1);
}
nb_values = nb_values_to_sum;
nb_values_to_sum >>= 1;
}
return array(0);
}
} // namespace Math
} // namespace akantu

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