/*
* Redberry: symbolic tensor computations.
*
* Copyright (c) 2010-2014:
* 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.core.indices;
import cc.redberry.core.groups.permutations.Permutation;
import cc.redberry.core.groups.permutations.Permutations;
import cc.redberry.core.utils.ArraysUtils;
import cc.redberry.core.utils.IntArrayList;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* Builder of simple indices. Constructs simple indices (correctly handling possible symmetries) by
* sequential append of other indices.
*
* @author Dmitry Bolotin
* @author Stanislav Poslavsky
* @since 1.0
*/
public final class SimpleIndicesBuilder {
private final IntArrayList data;
private final List<SymmetriesHolder> symmetries;
/**
* Construct builder with specified initial capacity.
*
* @param initialCapacity initial capacity
*/
public SimpleIndicesBuilder(int initialCapacity) {
data = new IntArrayList(initialCapacity);
symmetries = new ArrayList<>(initialCapacity);
}
/**
* Constructs empty builder.
*/
public SimpleIndicesBuilder() {
this(7);
}
/**
* Appends specified simple indices to this taking into account symmetries of passing indices.
*
* @param indices simple indices
* @return this
*/
public SimpleIndicesBuilder append(SimpleIndices indices) {
if (indices.size() == 0)
return this;
data.addAll(((AbstractSimpleIndices) indices).data);
symmetries.add(new SymmetriesHolder(indices.size(), indices.getSymmetries().getGenerators()));
return this;
}
/**
* Appends specified indices, represented as integer array to this. The passing indices are considered
* to have no any symmetries.
*
* @param indices integer array of indices
* @return this
*/
public SimpleIndicesBuilder append(int... indices) {
data.addAll(indices);
symmetries.add(new SymmetriesHolder(indices.length, Collections.EMPTY_LIST));
return this;
}
/**
* Appends specified indices. The passing indices are considered
* to have no any symmetries.
*
* @param indices indices
* @return this
*/
public SimpleIndicesBuilder appendWithoutSymmetries(Indices indices) {
if (indices.size() == 0)
return this;
data.addAll(((AbstractIndices) indices).data);
symmetries.add(new SymmetriesHolder(indices.size(), Collections.EMPTY_LIST));
return this;
}
/**
* Returns resulting {@code SimpleIndices}.
*
* @return resulting {@code SimpleIndices}
* @throws InconsistentIndicesException if there was more then one same index (with same names, types and states)
*/
public SimpleIndices getIndices() {
final int[] data = this.data.toArray();
//Sorting indices by type
int j;
int[] types = new int[data.length];
for (j = 0; j < data.length; ++j)
types[j] = data[j] & 0x7F000000;
int[] cosort = Permutations.createIdentityArray(data.length);
//only stable sort
ArraysUtils.stableSort(types, cosort);
int[] cosortInv = Permutations.inverse(cosort);
//Allocating resulting symmetries object
//it already contains identity symmetry
List<Permutation> resultingSymmetries = new ArrayList<>();
int[] c;
int position = 0;
//rescaling symmetries to the actual length and positions corresponding
//to the sorted indices
for (SymmetriesHolder holder : this.symmetries) {
for (Permutation s : holder.generators) {
c = new int[data.length];
for (j = 0; j < data.length; ++j)
if (cosort[j] < position || cosort[j] >= position + holder.length)
c[j] = j;
else
c[j] = cosortInv[s.newIndexOf(cosort[j] - position) + position];
resultingSymmetries.add(Permutations.createPermutation(s.antisymmetry(), c));
}
//increasing position in the total symmetry array
position += holder.length;
}
return IndicesFactory.createSimple(
IndicesSymmetries.create(new StructureOfIndices(data), resultingSymmetries), data);
}
private static final class SymmetriesHolder {
final int length;
final List<Permutation> generators;
private SymmetriesHolder(int length, List<Permutation> generators) {
this.length = length;
this.generators = generators;
}
}
}