/*
* Redberry: symbolic tensor computations.
*
* Copyright (c) 2010-2012:
* Stanislav Poslavsky <stvlpos@mail.ru>
* Bolotin Dmitriy <bolotin.dmitriy@gmail.com>
*
* This file is part of Redberry.
*
* Redberry 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.
*
* Redberry 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 Redberry. If not, see <http://www.gnu.org/licenses/>.
*/
package cc.redberry.transformation.integral;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import cc.redberry.core.indices.IndicesTypeStructure;
import cc.redberry.core.indices.SimpleIndices;
import cc.redberry.core.tensor.Integral;
import cc.redberry.core.tensor.SimpleTensor;
import cc.redberry.core.tensor.Sum;
import cc.redberry.core.tensor.Tensor;
import cc.redberry.core.tensor.TensorIterator;
import cc.redberry.core.indexmapping.IndexMappingDirect;
import cc.redberry.core.transformations.ApplyIndexMappingDirectTransformation;
import cc.redberry.transformation.Transformation;
import cc.redberry.transformation.substitutions.SubstitutionsFactory;
/**
*
* @author Stanislav Poslavsky
*/
public class CollectIntegralFromSum implements Transformation {
public static CollectIntegralFromSum INSTANCE = new CollectIntegralFromSum();
private CollectIntegralFromSum() {
}
@Override
public Tensor transform(final Tensor tensor) {
if (!(tensor instanceof Sum))
return tensor;
final IntegralIP iP = new IntegralIP();
final TensorIterator iterator = tensor.iterator();
Tensor current;
while (iterator.hasNext()) {
current = iterator.next();
if (current instanceof Integral) {
iP.put((Integral) current);
iterator.remove();
}
}
((Sum) tensor).add(iP.result());
return tensor.equivalent();
}
private static class IntegralIP {
List<Integral> integrals = new ArrayList<>();
void put(final Integral integral) {
for (Integral current : integrals) {
final Transformation[] subs = getSubs(integral.vars(), current.vars());
if (subs == null)
continue;
Tensor target = integral.target();
for (Transformation sub : subs)
target = sub.transform(target);
current.setTarget(new Sum(current.target(), target));
return;
}
integrals.add(integral);
}
Transformation[] getSubs(final SimpleTensor[] from, final SimpleTensor[] to) {
int length;
if ((length = from.length) != to.length)
return null;
Arrays.sort(from, IndicesComparator.INSTANCE);
Arrays.sort(to, IndicesComparator.INSTANCE);
final Transformation[] subs = new Transformation[length];
SimpleIndices fromIndices, toIndices;
for (int i = 0; i < length; ++i) {
if (!(fromIndices = from[i].getIndices()).similarTypeStructure((toIndices = to[i].getIndices())))
return null;
final IndexMappingDirect im = new IndexMappingDirect(fromIndices, toIndices);
ApplyIndexMappingDirectTransformation.INSTANCE.perform(from[i], im);
subs[i] = SubstitutionsFactory.createSubstitution(from[i], to[i]);
}
return subs;
}
Tensor result() {
return new Sum(integrals);
}
private static class IndicesComparator implements Comparator<SimpleTensor> {
static IndicesComparator INSTANCE = new IndicesComparator();
@Override
public int compare(final SimpleTensor o1, final SimpleTensor o2) {
final SimpleIndices i1 = o1.getIndices(), i2 = o2.getIndices();
if (i1.size() < i2.size())
return -1;
if (i1.size() > i2.size())
return 1;
final IndicesTypeStructure s1 = new IndicesTypeStructure(i1), s2 = new IndicesTypeStructure(i2);
return Integer.compare(s1.hashCode(), s2.hashCode());
}
}
}
}