cc.redberry.core.graph.PrimitiveSubgraphPartition Maven / Gradle / Ivy
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Redberry is an open source computer algebra system designed for tensor
manipulation. It implements basic computer algebra system routines as well as
complex tools for real computations in physics.
This is Redberry core, which contains the implementation of the basic
computer algebra routines and general-purpose transformations.
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/*
* Redberry: symbolic tensor computations.
*
* Copyright (c) 2010-2015:
* Stanislav Poslavsky
* Bolotin Dmitriy
*
* 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 subgraphs = new ArrayList<>();
for (int pivot = 0; pivot < size; ++pivot)
if (pc.get(pivot).getIndices().size(type) != 0 && !used.get(pivot))
subgraphs.add(calculateComponent(pivot));
return subgraphs.toArray(new PrimitiveSubgraph[subgraphs.size()]);
}
private PrimitiveSubgraph calculateComponent(final int pivot) {
ArrayDeque positions = new ArrayDeque<>();
positions.add(pivot);
int[] left, right;
left = right = getLinks(pivot);
assert left[0] != NO_LINKS || left[1] != NO_LINKS;
if (left[0] == BRANCHING || left[1] == BRANCHING)
return processGraph(pivot);
if (left[0] == left[1] && left[0] == pivot) {
used.set(pivot);
return new PrimitiveSubgraph(GraphType.Cycle, new int[]{pivot});
}
int leftPivot, rightPivot, lastLeftPivot = NOT_INITIALIZED, lastRightPivot = NOT_INITIALIZED;
while (left != DUMMY || right != DUMMY) {
if (left[0] == BRANCHING || left[1] == BRANCHING || right[0] == BRANCHING || right[1] == BRANCHING)
return processGraph(pivot);
leftPivot = left[0];
rightPivot = right[1];
assert leftPivot < 0 || !used.get(leftPivot);
assert rightPivot < 0 || !used.get(rightPivot);
//Left end detection
if (leftPivot == NO_LINKS || leftPivot == -1)
leftPivot = DUMMY_PIVOT;
//Right end detection
if (rightPivot == NO_LINKS || rightPivot == -1)
rightPivot = DUMMY_PIVOT;
//Odd cycle detection
if (leftPivot >= 0 && leftPivot == lastRightPivot) {
//Closing odd nodes number cycle
assert rightPivot == lastLeftPivot;
return new PrimitiveSubgraph(GraphType.Cycle, deque2array(positions));
}
//Adding left pivot before cycle detection (if cycle, not to add closing node twice)
if (leftPivot >= 0)
positions.addFirst(leftPivot);
//Even cycle detection
if (leftPivot >= 0 && leftPivot == rightPivot) {
left = getLinks(leftPivot);
// Checking next (cycle closing) node
if (left[0] == BRANCHING || left[1] == BRANCHING)
return processGraph(pivot);
return new PrimitiveSubgraph(GraphType.Cycle, deque2array(positions));
}
//Adding right pivot
if (rightPivot >= 0)
positions.addLast(rightPivot);
//Needed in odd cycle detection
lastLeftPivot = leftPivot;
//Redundant (needed for assertion)
lastRightPivot = rightPivot;
//Next layer (breadth-first traversal)
left = getLinks(leftPivot);
right = getLinks(rightPivot);
}
return new PrimitiveSubgraph(GraphType.Line, deque2array(positions));
}
private int[] deque2array(ArrayDeque deque) {
int[] arr = new int[deque.size()];
int i = -1;
for (Integer ii : deque) {
arr[++i] = ii;
used.set(ii);
}
return arr;
}
private static final int BRANCHING = -3, NO_LINKS = -2, NOT_INITIALIZED = -4, DUMMY_PIVOT = -5;
private static final int[] DUMMY = new int[]{DUMMY_PIVOT, DUMMY_PIVOT};
private int[] getLinks(final int pivot) {
if (pivot == DUMMY_PIVOT)
return DUMMY;
assert pivot >= 0;
final int[] links = {NOT_INITIALIZED, NOT_INITIALIZED};
final long[] contractions = fcs.contractions[pivot];
Indices indices = pc.get(pivot).getIndices();
int index, toTensorIndex;
for (int i = contractions.length - 1; i >= 0; --i) {
index = indices.get(i);
if (getType(index) != type.getType())
continue;
toTensorIndex = getToTensorIndex(contractions[i]);
int state = 1 - getStateInt(index);
if (links[state] >= -1 && links[state] != toTensorIndex)
links[state] = BRANCHING;
if (links[state] == NOT_INITIALIZED)
links[state] = toTensorIndex;
}
if (links[0] == NOT_INITIALIZED)
links[0] = NO_LINKS;
if (links[1] == NOT_INITIALIZED)
links[1] = NO_LINKS;
return links;
}
private PrimitiveSubgraph processGraph(int pivot) {
IntArrayList positions = new IntArrayList();
positions.add(pivot);
IntArrayList stack = new IntArrayList();
stack.push(pivot);
used.set(pivot);
long[] contractions;
Indices indices;
int currentPivot, index, toTensorIndex;
while (!stack.isEmpty()) {
currentPivot = stack.pop();
indices = pc.get(currentPivot).getIndices();
contractions = fcs.contractions[currentPivot];
for (int i = contractions.length - 1; i >= 0; --i) {
index = indices.get(i);
if (getType(index) != type.getType())
continue;
toTensorIndex = getToTensorIndex(contractions[i]);
if (toTensorIndex == -1 || used.get(toTensorIndex))
continue;
used.set(toTensorIndex);
positions.add(toTensorIndex);
stack.push(toTensorIndex);
}
}
return new PrimitiveSubgraph(GraphType.Graph, positions.toArray());
}
}