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Morfologik Finite State Automata Builder
package morfologik.fsa.builders;
import static morfologik.fsa.CFSA2.*;
import static morfologik.fsa.FSAFlags.*;
import java.io.IOException;
import java.io.OutputStream;
import java.util.BitSet;
import java.util.Comparator;
import java.util.EnumSet;
import java.util.Locale;
import java.util.PriorityQueue;
import java.util.Set;
import java.util.TreeSet;
import java.util.logging.Level;
import java.util.logging.Logger;
import com.carrotsearch.hppc.BoundedProportionalArraySizingStrategy;
import com.carrotsearch.hppc.IntArrayList;
import com.carrotsearch.hppc.IntIntHashMap;
import com.carrotsearch.hppc.IntStack;
import com.carrotsearch.hppc.cursors.IntCursor;
import com.carrotsearch.hppc.cursors.IntIntCursor;
import morfologik.fsa.CFSA2;
import morfologik.fsa.FSA;
import morfologik.fsa.FSAFlags;
import morfologik.fsa.FSAHeader;
import morfologik.fsa.StateVisitor;
import morfologik.fsa.builders.FSAUtils.IntIntHolder;
/**
* Serializes in-memory {@link FSA} graphs to {@link CFSA2}.
*
*
* It is possible to serialize the automaton with numbers required for perfect
* hashing. See {@link #withNumbers()} method.
*
*
* @see CFSA2
*/
public final class CFSA2Serializer implements FSASerializer {
private final Logger logger = Logger.getLogger(getClass().getName());
/**
* Supported flags.
*/
private final static EnumSet flags = EnumSet.of(NUMBERS, FLEXIBLE, STOPBIT, NEXTBIT);
/**
* No-state id.
*/
private final static int NO_STATE = -1;
/**
* true if we should serialize with numbers.
*
* @see #withNumbers()
*/
private boolean withNumbers;
/**
* A hash map of [state, offset] pairs.
*/
private IntIntHashMap offsets = new IntIntHashMap();
/**
* A hash map of [state, right-language-count] pairs.
*/
private IntIntHashMap numbers = new IntIntHashMap();
/**
* Scratch array for serializing vints.
*/
private final byte[] scratch = new byte[5];
/**
* The most frequent labels for integrating with the flags field.
*/
private byte[] labelsIndex;
/**
* Inverted index of labels to be integrated with flags field. A label at
* index i has the index or zero (no integration).
*/
private int[] labelsInvIndex;
/**
* Serialize the automaton with the number of right-language sequences in each
* node. This is required to implement perfect hashing. The numbering also
* preserves the order of input sequences.
*
* @return Returns the same object for easier call chaining.
*/
public CFSA2Serializer withNumbers() {
withNumbers = true;
return this;
}
/**
* Serializes any {@link FSA} to {@link CFSA2} stream.
*
* @see #withNumbers()
* @return Returns os for chaining.
*/
@Override
public T serialize(final FSA fsa, T os) throws IOException {
/*
* Calculate the most frequent labels and build indexed labels dictionary.
*/
computeLabelsIndex(fsa);
/*
* Calculate the number of bytes required for the node data, if
* serializing with numbers.
*/
if (withNumbers) {
this.numbers = FSAUtils.rightLanguageForAllStates(fsa);
}
/*
* Linearize all the states, optimizing their layout.
*/
IntArrayList linearized = linearize(fsa);
/*
* Emit the header.
*/
FSAHeader.write(os, CFSA2.VERSION);
EnumSet fsaFlags = EnumSet.of(FLEXIBLE, STOPBIT, NEXTBIT);
if (withNumbers) {
fsaFlags.add(NUMBERS);
}
final short sflags = FSAFlags.asShort(fsaFlags);
os.write((sflags >> 8) & 0xFF);
os.write((sflags) & 0xFF);
/*
* Emit labels index.
*/
os.write(labelsIndex.length);
os.write(labelsIndex);
/*
* Emit the automaton.
*/
int size = emitNodes(fsa, os, linearized);
assert size == 0 : "Size changed in the final pass?";
return os;
}
/**
* Compute a set of labels to be integrated with the flags field.
*/
private void computeLabelsIndex(final FSA fsa) {
// Compute labels count.
final int[] countByValue = new int[256];
fsa.visitAllStates(new StateVisitor() {
public boolean accept(int state) {
for (int arc = fsa.getFirstArc(state); arc != 0; arc = fsa.getNextArc(arc))
countByValue[fsa.getArcLabel(arc) & 0xff]++;
return true;
}
});
// Order by descending frequency of counts and increasing label value.
Comparator comparator = new Comparator() {
public int compare(IntIntHolder o1, IntIntHolder o2) {
int countDiff = o2.b - o1.b;
if (countDiff == 0) {
countDiff = o1.a - o2.a;
}
return countDiff;
}
};
TreeSet labelAndCount = new TreeSet(comparator);
for (int label = 0; label < countByValue.length; label++) {
if (countByValue[label] > 0) {
labelAndCount.add(new IntIntHolder(label, countByValue[label]));
}
}
labelsIndex = new byte[1 + Math.min(labelAndCount.size(), CFSA2.LABEL_INDEX_SIZE)];
labelsInvIndex = new int[256];
for (int i = labelsIndex.length - 1; i > 0 && !labelAndCount.isEmpty(); i--) {
IntIntHolder p = labelAndCount.first();
labelAndCount.remove(p);
labelsInvIndex[p.a] = i;
labelsIndex[i] = (byte) p.a;
}
}
/**
* Return supported flags.
*/
@Override
public Set getFlags() {
return flags;
}
/**
* Linearization of states.
*/
private IntArrayList linearize(final FSA fsa) throws IOException {
/*
* Compute the states with most inlinks. These should be placed as close to the
* start of the automaton, as possible so that v-coded addresses are tiny.
*/
final IntIntHashMap inlinkCount = computeInlinkCount(fsa);
/*
* An array of ordered states for serialization.
*/
final IntArrayList linearized = new IntArrayList(0, new BoundedProportionalArraySizingStrategy(1000, 10000, 1.5f));
/*
* Determine which states should be linearized first (at fixed positions) so as to
* minimize the place occupied by goto fields.
*/
int maxStates = Integer.MAX_VALUE;
int minInlinkCount = 2;
int [] states = computeFirstStates(inlinkCount, maxStates, minInlinkCount);
/*
* Compute initial addresses, without node rearrangements.
*/
int serializedSize = linearizeAndCalculateOffsets(fsa, new IntArrayList(), linearized, offsets);
/*
* Probe for better node arrangements by selecting between [lower, upper]
* nodes from the potential candidate nodes list.
*/
IntArrayList sublist = new IntArrayList();
sublist.buffer = states;
sublist.elementsCount = states.length;
/*
* Probe the initial region a little bit, looking for optimal cut. It can't be binary search
* because the result isn't monotonic.
*/
log(Level.FINE, "Compacting, initial output size: %,d", serializedSize);
int cutAt = 0;
for (int cut = Math.min(25, states.length); cut <= Math.min(150, states.length); cut += 25) {
sublist.elementsCount = cut;
int newSize = linearizeAndCalculateOffsets(fsa, sublist, linearized, offsets);
log(Level.FINE, "Moved %,d states, output size: %,d", sublist.size(), newSize);
if (newSize >= serializedSize) {
break;
}
cutAt = cut;
}
/*
* Cut at the calculated point and repeat linearization.
*/
sublist.elementsCount = cutAt;
int size = linearizeAndCalculateOffsets(fsa, sublist, linearized, offsets);
log(Level.FINE, "%,d states moved, final size: %,d", sublist.size(), size);
return linearized;
}
private void log(Level level, String msg, Object... args) {
logger.log(level, String.format(Locale.ROOT, msg, args));
}
/**
* Linearize all states, putting states in front of the automaton
* and calculating stable state offsets.
*/
private int linearizeAndCalculateOffsets(FSA fsa, IntArrayList states, IntArrayList linearized,
IntIntHashMap offsets) throws IOException {
final BitSet visited = new BitSet();
final IntStack nodes = new IntStack();
linearized.clear();
/*
* Linearize states with most inlinks first.
*/
for (int i = 0; i < states.size(); i++) {
linearizeState(fsa, nodes, linearized, visited, states.get(i));
}
/*
* Linearize the remaining states by chaining them one after another, in depth-order.
*/
nodes.push(fsa.getRootNode());
while (!nodes.isEmpty()) {
final int node = nodes.pop();
if (visited.get(node))
continue;
linearizeState(fsa, nodes, linearized, visited, node);
}
/*
* Calculate new state offsets. This is iterative. We start with
* maximum potential offsets and recalculate until converged.
*/
int MAX_OFFSET = Integer.MAX_VALUE;
for (IntCursor c : linearized) {
offsets.put(c.value, MAX_OFFSET);
}
int i, j = 0;
while ((i = emitNodes(fsa, null, linearized)) > 0) {
j = i;
}
return j;
}
/**
* Add a state to linearized list.
*/
private void linearizeState(final FSA fsa, IntStack nodes, IntArrayList linearized, BitSet visited, int node) {
linearized.add(node);
visited.set(node);
for (int arc = fsa.getFirstArc(node); arc != 0; arc = fsa.getNextArc(arc)) {
if (!fsa.isArcTerminal(arc)) {
final int target = fsa.getEndNode(arc);
if (!visited.get(target))
nodes.push(target);
}
}
}
/**
* Compute the set of states that should be linearized first to minimize other
* states goto length.
*/
private int[] computeFirstStates(IntIntHashMap inlinkCount, int maxStates, int minInlinkCount) {
Comparator comparator = new Comparator() {
public int compare(IntIntHolder o1, IntIntHolder o2) {
int v = o1.a - o2.a;
return v == 0 ? (o1.b - o2.b) : v;
}
};
PriorityQueue stateInlink = new PriorityQueue(1, comparator);
IntIntHolder scratch = new IntIntHolder();
for (IntIntCursor c : inlinkCount) {
if (c.value > minInlinkCount) {
scratch.a = c.value;
scratch.b = c.key;
if (stateInlink.size() < maxStates || comparator.compare(scratch, stateInlink.peek()) > 0) {
stateInlink.add(new IntIntHolder(c.value, c.key));
if (stateInlink.size() > maxStates) {
stateInlink.remove();
}
}
}
}
int [] states = new int [stateInlink.size()];
for (int position = states.length; !stateInlink.isEmpty();) {
IntIntHolder i = stateInlink.remove();
states[--position] = i.b;
}
return states;
}
/**
* Compute in-link count for each state.
*/
private IntIntHashMap computeInlinkCount(final FSA fsa) {
IntIntHashMap inlinkCount = new IntIntHashMap();
BitSet visited = new BitSet();
IntStack nodes = new IntStack();
nodes.push(fsa.getRootNode());
while (!nodes.isEmpty()) {
final int node = nodes.pop();
if (visited.get(node))
continue;
visited.set(node);
for (int arc = fsa.getFirstArc(node); arc != 0; arc = fsa.getNextArc(arc)) {
if (!fsa.isArcTerminal(arc)) {
final int target = fsa.getEndNode(arc);
inlinkCount.putOrAdd(target, 1, 1);
if (!visited.get(target))
nodes.push(target);
}
}
}
return inlinkCount;
}
/**
* Update arc offsets assuming the given goto length.
*/
private int emitNodes(FSA fsa, OutputStream os, IntArrayList linearized) throws IOException {
int offset = 0;
// Add epsilon state.
offset += emitNodeData(os, 0);
if (fsa.getRootNode() != 0)
offset += emitArc(os, BIT_LAST_ARC, (byte) '^', offsets.get(fsa.getRootNode()));
else
offset += emitArc(os, BIT_LAST_ARC, (byte) '^', 0);
boolean offsetsChanged = false;
final int max = linearized.size();
for (IntCursor c : linearized) {
final int state = c.value;
final int nextState = c.index + 1 < max ? linearized.get(c.index + 1) : NO_STATE;
if (os == null) {
offsetsChanged |= (offsets.get(state) != offset);
offsets.put(state, offset);
} else {
assert offsets.get(state) == offset : state + " " + offsets.get(state) + " " + offset;
}
offset += emitNodeData(os, withNumbers ? numbers.get(state) : 0);
offset += emitNodeArcs(fsa, os, state, nextState);
}
return offsetsChanged ? offset : 0;
}
/**
* Emit all arcs of a single node.
*/
private int emitNodeArcs(FSA fsa, OutputStream os, final int state, final int nextState) throws IOException {
int offset = 0;
for (int arc = fsa.getFirstArc(state); arc != 0; arc = fsa.getNextArc(arc)) {
int targetOffset;
final int target;
if (fsa.isArcTerminal(arc)) {
target = 0;
targetOffset = 0;
} else {
target = fsa.getEndNode(arc);
targetOffset = offsets.get(target);
}
int flags = 0;
if (fsa.isArcFinal(arc)) {
flags |= BIT_FINAL_ARC;
}
if (fsa.getNextArc(arc) == 0) {
flags |= BIT_LAST_ARC;
}
if (targetOffset != 0 && target == nextState) {
flags |= BIT_TARGET_NEXT;
targetOffset = 0;
}
offset += emitArc(os, flags, fsa.getArcLabel(arc), targetOffset);
}
return offset;
}
/** */
private int emitArc(OutputStream os, int flags, byte label, int targetOffset) throws IOException {
int length = 0;
int labelIndex = labelsInvIndex[label & 0xff];
if (labelIndex > 0) {
if (os != null)
os.write(flags | labelIndex);
length++;
} else {
if (os != null) {
os.write(flags);
os.write(label);
}
length += 2;
}
if ((flags & BIT_TARGET_NEXT) == 0) {
int len = writeVInt(scratch, 0, targetOffset);
if (os != null) {
os.write(scratch, 0, len);
}
length += len;
}
return length;
}
/** */
private int emitNodeData(OutputStream os, int number) throws IOException {
int size = 0;
if (withNumbers) {
size = writeVInt(scratch, 0, number);
if (os != null) {
os.write(scratch, 0, size);
}
}
return size;
}
/** */
@Override
public CFSA2Serializer withFiller(byte filler) {
throw new UnsupportedOperationException("CFSA2 does not support filler. Use .info file.");
}
/** */
@Override
public CFSA2Serializer withAnnotationSeparator(byte annotationSeparator) {
throw new UnsupportedOperationException("CFSA2 does not support separator. Use .info file.");
}
/**
* Write a v-int to a byte array.
*/
static int writeVInt(byte[] array, int offset, int value) {
assert value >= 0 : "Can't v-code negative ints.";
while (value > 0x7F) {
array[offset++] = (byte) (0x80 | (value & 0x7F));
value >>= 7;
}
array[offset++] = (byte) value;
return offset;
}
}