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/*
* File: SparseVector.java
* Authors: Jeremy D. Wendt
* Company: Sandia National Laboratories
* Project: Cognitive Foundry
*
* Copyright 2015, Sandia Corporation. Under the terms of Contract
* DE-AC04-94AL85000, there is a non-exclusive license for use of this work by
* or on behalf of the U.S. Government. Export of this program may require a
* license from the United States Government. See CopyrightHistory.txt for
* complete details.
*/
package gov.sandia.cognition.math.matrix.custom;
import gov.sandia.cognition.math.MutableDouble;
import gov.sandia.cognition.math.matrix.Matrix;
import gov.sandia.cognition.math.matrix.Vector;
import gov.sandia.cognition.math.matrix.VectorEntry;
import gov.sandia.cognition.math.matrix.VectorFactory;
import gov.sandia.cognition.util.ArgumentChecker;
import java.util.Arrays;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;
/**
* Our sparse vector implementation. Rather straightforward: stores all non-zero
* data in a map from index to value.
*
* @author Jeremy D. Wendt
* @since 3.4.3
*/
public class SparseVector
extends BaseVector
{
/**
* Sparse matrices and vectors appear to be less effective after passing
* this threshold
*/
static final double SPARSE_TO_DENSE_THRESHOLD = 0.25;
/**
* The vector length
*/
final private int dimensionality;
/**
* The index-to-value map
*/
private TreeMap elements;
/**
* Compressed version of the data: The values. Similar to the Yale format
* for sparse matrices.
*/
private double[] values;
/**
* Compressed version of the data: The locations. Similar to the Yale format
* for sparse matrices.
*/
private int[] indices;
/**
* Create a new sparse vector. All values begin empty (which is interpreted
* to 0).
*
* @param n The vector length
*/
public SparseVector(
final int n)
{
ArgumentChecker.assertIsNonNegative("dimensionality", n);
this.dimensionality = n;
elements = new TreeMap<>();
values = null;
indices = null;
}
/**
* Copy constructor -- creates a deep copy of the input sparse vector.
*
* @param v The sparse vector to copy
*/
public SparseVector(
final SparseVector v)
{
this.dimensionality = v.dimensionality;
if (!v.isCompressed())
{
elements = new TreeMap<>(v.elements);
// Need to copy over all the values.
for (Map.Entry entry : this.elements.entrySet())
{
entry.setValue(new MutableDouble(entry.getValue()));
}
values = null;
indices = null;
}
else
{
elements = new TreeMap<>();
values = Arrays.copyOf(v.values, v.values.length);
indices = Arrays.copyOf(v.indices, v.indices.length);
}
}
/**
* Copy constructor -- creates a deep copy of the input sparse vector.
*
* @param v The sparse vector to copy
*/
public SparseVector(
final DenseVector v)
{
this.dimensionality = v.values.length;
int nnz = v.countNonZeros();
values = new double[nnz];
indices = new int[nnz];
elements = new TreeMap<>();
int idx = 0;
for (int i = 0; i < dimensionality; ++i)
{
double val = v.values[i];
if (val != 0)
{
values[idx] = val;
indices[idx] = i;
++idx;
}
}
}
/**
* This should never be called by anything or anyone other than Java's
* serialization code.
*/
protected SparseVector()
{
// NOTE: This initializes to bad values or nothing
dimensionality = 0;
}
/**
* The compressed representation should allow for quicker mathematical
* operations, but does not permit editing the values in the vector. This
* returns true if the vector is currently compressed, false if not
* compressed.
*
* @return true if the vector is currently compressed, false if not
* compressed.
*/
final public boolean isCompressed()
{
return (values != null) && (indices != null);
}
/**
* The compressed representation should allow for quicker mathematical
* operations, but does not permit editing the values in the vector. This
* transitions from the uncompressed to the compressed form. If already
* compressed, this does nothing.
*/
final public void compress()
{
if (isCompressed())
{
return;
}
int nnz = elements.size();
values = new double[nnz];
indices = new int[nnz];
int idx = 0;
for (Map.Entry e : elements.entrySet())
{
indices[idx] = e.getKey();
values[idx] = e.getValue().value;
++idx;
}
elements.clear();
}
/**
* The compressed representation should allow for quicker mathematical
* operations, but does not permit editing the values in the vector. This
* transitions from the compressed to the uncompressed form. If already
* uncompressed, this does nothing.
*/
final public void decompress()
{
if (!isCompressed())
{
return;
}
elements.clear();
for (int i = 0; i < values.length; ++i)
{
final double value = values[i];
if (value != 0.0)
{
elements.put(indices[i], new MutableDouble(value));
}
}
indices = null;
values = null;
}
@Override
public void zero()
{
this.elements.clear();
this.indices = null;
this.values = null;
}
@Override
final public SparseVector clone()
{
final SparseVector clone = (SparseVector) super.clone();
if (!this.isCompressed())
{
clone.elements = new TreeMap<>(this.elements);
// Need to copy over all the values.
for (Map.Entry entry : clone.elements.entrySet())
{
entry.setValue(new MutableDouble(entry.getValue()));
}
clone.values = null;
clone.indices = null;
}
else
{
clone.elements = new TreeMap<>();
clone.values = Arrays.copyOf(this.values, this.values.length);
clone.indices = Arrays.copyOf(this.indices, this.indices.length);
}
return clone;
}
@Override
final public Vector plus(
final Vector v)
{
// I need to flip this so that if it the input is a dense vector, I
// return a dense vector. If it's a sparse vector, then a sparse vector
// is still returned.
Vector result = v.clone();
result.plusEquals(this);
return result;
}
@Override
final public Vector minus(
final Vector v)
{
// I need to flip this so that if it the input is a dense vector, I
// return a dense vector. If it's a sparse vector, then a sparse vector
// is still returned.
Vector result = v.clone();
result.negativeEquals();
result.plusEquals(this);
return result;
}
/**
* Counts the number of non-zero operations after a sparse-on-spares
* operation.
*
* @param other The other vector
* @param op The operation to perform (addition/subtraction = OR, dot
* product = AND)
* @return The number of non-zero entries after the operation -- ignoring
* zeroes generated by the actual operation (2 - 2 = 0) -- just counting
* locations where operations will occur.
*/
private int numNonZeroAfterOp(
final SparseVector other,
final SparseMatrix.Combiner op)
{
compress();
other.compress();
int myidx = 0;
int otheridx = 0;
int nnz = 0;
while ((myidx < indices.length) && (otheridx < other.indices.length))
{
if (indices[myidx] == other.indices[otheridx])
{
++nnz;
++myidx;
++otheridx;
}
else if (indices[myidx] < other.indices[otheridx])
{
if (op == SparseMatrix.Combiner.OR)
{
++nnz;
}
++myidx;
}
else if (other.indices[otheridx] < indices[myidx])
{
if (op == SparseMatrix.Combiner.OR)
{
++nnz;
}
++otheridx;
}
}
if (op == SparseMatrix.Combiner.OR)
{
nnz += indices.length - myidx;
nnz += other.indices.length - otheridx;
}
return nnz;
}
/**
* {@inheritDoc}
*
* NOTE: This operation is not recommended as it is most likely to create a
* very dense vector being stored in a sparse-vector format. This will be
* memory inefficient.
*/
@Override
public void scaledPlusEquals(
final DenseVector other,
final double scaleFactor)
{
this.assertSameDimensionality(other);
compress();
// Just assume that this is going to be a new dense vector.
// Use these as the "output" and local vals and locs as current vals
double[] valsAfter = new double[dimensionality];
int[] locsAfter = new int[dimensionality];
int idx = 0;
for (int i = 0; i < dimensionality; ++i)
{
if ((idx < indices.length) && indices[idx] == i)
{
valsAfter[i] = values[idx] + other.values[i] * scaleFactor;
++idx;
}
else
{
valsAfter[i] = other.values[i] * scaleFactor;
}
locsAfter[i] = i;
}
values = valsAfter;
indices = locsAfter;
}
@Override
public void scaledPlusEquals(
final SparseVector other,
final double scaleFactor)
{
this.assertSameDimensionality(other);
compress();
int nnz = numNonZeroAfterOp(other, SparseMatrix.Combiner.OR);
double[] valsAfter = new double[nnz];
int[] locsAfter = new int[nnz];
int myidx = 0;
int otheridx = 0;
int outidx = 0;
while ((myidx < values.length) && (otheridx < other.values.length))
{
if (indices[myidx] == other.indices[otheridx])
{
valsAfter[outidx] = values[myidx] + other.values[otheridx] * scaleFactor;
locsAfter[outidx] = indices[myidx];
++myidx;
++otheridx;
}
else if (indices[myidx] < other.indices[otheridx])
{
valsAfter[outidx] = values[myidx];
locsAfter[outidx] = indices[myidx];
++myidx;
}
else // if (other.locs[otheridx] < locs[myidx])
{
valsAfter[outidx] = other.values[otheridx] * scaleFactor;
locsAfter[outidx] = other.indices[otheridx];
++otheridx;
}
++outidx;
}
while (myidx < values.length)
{
valsAfter[outidx] = values[myidx];
locsAfter[outidx] = indices[myidx];
++myidx;
++outidx;
}
while (otheridx < other.values.length)
{
valsAfter[outidx] = other.values[otheridx] * scaleFactor;
locsAfter[outidx] = other.indices[otheridx];
++otheridx;
++outidx;
}
values = valsAfter;
indices = locsAfter;
}
/**
* {@inheritDoc}
*
* NOTE: This operation is not recommended as it is most likely to create a
* very dense vector being stored in a sparse-vector format. This will be
* memory inefficient.
*/
@Override
public final void plusEquals(
final DenseVector other)
{
this.scaledPlusEquals(other, 1.0);
}
@Override
public final void plusEquals(
final SparseVector other)
{
this.scaledPlusEquals(other, 1.0);
}
/**
* {@inheritDoc}
*
* NOTE: This operation is not recommended as it is most likely to create a
* very dense vector being stored in a sparse-vector format. This will be
* memory inefficient.
*/
@Override
public final void minusEquals(
final DenseVector other)
{
this.scaledPlusEquals(other, -1.0);
}
@Override
public final void minusEquals(
final SparseVector other)
{
this.scaledPlusEquals(other, -1.0);
}
@Override
public final void dotTimesEquals(
final DenseVector other)
{
this.assertSameDimensionality(other);
compress();
for (int i = 0; i < values.length; ++i)
{
values[i] *= other.values[indices[i]];
}
}
@Override
public final void dotTimesEquals(
final SparseVector other)
{
this.assertSameDimensionality(other);
compress();
other.compress();
int nnz = numNonZeroAfterOp(other, SparseMatrix.Combiner.AND);
double[] valsAfter = new double[nnz];
int[] locsAfter = new int[nnz];
int outidx = 0;
int otheridx = 0;
for (int i = 0; i < values.length; ++i)
{
while (other.indices[otheridx] < indices[i])
{
++otheridx;
}
if (other.indices[otheridx] == indices[i])
{
valsAfter[outidx] = values[i] * other.values[otheridx];
locsAfter[outidx] = indices[i];
++outidx;
++otheridx;
}
}
values = valsAfter;
indices = locsAfter;
}
@Override
public final double euclideanDistanceSquared(
final DenseVector other)
{
this.assertSameDimensionality(other);
compress();
double dist = 0;
int idx = 0;
for (int i = 0; i < dimensionality; ++i)
{
double tmp = other.values[i];
if ((idx < indices.length) && (indices[idx] == i))
{
tmp -= values[idx];
++idx;
}
dist += tmp * tmp;
}
return dist;
}
@Override
public final double euclideanDistanceSquared(
final SparseVector other)
{
this.assertSameDimensionality(other);
compress();
other.compress();
int myidx = 0;
int otheridx = 0;
double dist = 0;
while ((myidx < values.length) && (otheridx < other.values.length))
{
double tmp;
if (indices[myidx] == other.indices[otheridx])
{
tmp = values[myidx] - other.values[otheridx];
++myidx;
++otheridx;
}
else if (indices[myidx] < other.indices[otheridx])
{
tmp = values[myidx];
++myidx;
}
else // if (other.locs[otheridx] < locs[myidx])
{
tmp = other.values[otheridx];
++otheridx;
}
dist += tmp * tmp;
}
// Only one of the following while loops (if either) should ever occur -- not both.
while (myidx < values.length)
{
dist += values[myidx] * values[myidx];
++myidx;
}
while (otheridx < other.values.length)
{
dist += other.values[otheridx] * other.values[otheridx];
++otheridx;
}
return dist;
}
@Override
public final Matrix outerProduct(
final DenseVector other)
{
compress();
int numRows = getDimensionality();
int numCols = other.getDimensionality();
// This is debatable. The issue is that each row is likely to be dense,
// but many rows are likely to be completely empty. My current thinking
// is that storing the empty rows as dense vectors is a complete waste,
// and the additional overehead of storing the dense rows as sparse
// vectors is decreased when the sparse matrix is optimized.
SparseMatrix result = new SparseMatrix(numRows, numCols, true);
int idx = 0;
for (int i = 0; i < numRows; ++i)
{
SparseVector row = new SparseVector(numCols);
if ((idx < indices.length) && (indices[idx] == i))
{
for (int j = 0; j < numCols; ++j)
{
row.elements.put(j, new MutableDouble(values[idx] * other.values[j]));
}
++idx;
}
result.setRowInternal(i, row);
}
return result;
}
@Override
public final Matrix outerProduct(
final SparseVector other)
{
compress();
other.compress();
int numRows = getDimensionality();
int numCols = other.getDimensionality();
SparseMatrix result = new SparseMatrix(numRows, numCols, true);
int idx = 0;
for (int i = 0; i < numRows; ++i)
{
SparseVector row = new SparseVector(numCols);
if ((idx < indices.length) && (indices[idx] == i))
{
for (int j = 0; j < other.indices.length; ++j)
{
row.elements.put(other.indices[j], new MutableDouble(values[idx] * other.values[j]));
}
++idx;
}
result.setRowInternal(i, row);
}
return result;
}
@Override
public final Vector stack(
final DenseVector other)
{
compress();
Vector result;
int len = dimensionality + other.values.length;
int nnz = countNonZeros() + other.countNonZeros();
if (nnz > SPARSE_TO_DENSE_THRESHOLD * len)
{
result = new DenseVector(len);
}
else
{
result = new SparseVector(len);
}
// NOTE: The below could be faster (and I could get rid of all of the
// "setElement"s if I wanted to write two versions of this method. As
// it's likely to be infrequently called, I don't want to increase code
// complexity for a minimal gain.
int idx = 0;
for (int i = 0; i < dimensionality; ++i)
{
if ((idx < indices.length) && (indices[idx] == i))
{
result.setElement(i, values[idx]);
++idx;
}
else
{
result.setElement(i, 0);
}
}
for (int i = 0; i < other.values.length; ++i)
{
result.setElement(dimensionality + i, other.values[i]);
}
return result;
}
@Override
public final Vector stack(
final SparseVector other)
{
compress();
other.compress();
int len = dimensionality + other.dimensionality;
int nnz = countNonZeros() + other.countNonZeros();
SparseVector result = new SparseVector(len);
result.values = new double[nnz];
result.indices = new int[nnz];
int idx = 0;
for (int i = 0; i < indices.length; ++i)
{
result.values[idx] = values[i];
result.indices[idx] = indices[i];
++idx;
}
for (int i = 0; i < other.indices.length; ++i)
{
result.values[idx] = other.values[i];
result.indices[idx] = other.indices[i] + dimensionality;
++idx;
}
return result;
}
@Override
public final double dotProduct(
final SparseVector other)
{
this.assertSameDimensionality(other);
compress();
other.compress();
double result = 0;
int otheridx = 0;
final int thisLength = this.indices.length;
final int otherLength = other.indices.length;
for (int i = 0; i < thisLength && otheridx < otherLength; ++i)
{
while (other.indices[otheridx] < indices[i])
{
++otheridx;
if (otheridx >= otherLength)
{
return result;
}
}
if (other.indices[otheridx] == indices[i])
{
result += values[i] * other.values[otheridx];
++otheridx;
}
}
return result;
}
@Override
public final double dotProduct(
final DenseVector other)
{
this.assertSameDimensionality(other);
compress();
double result = 0;
for (int i = 0; i < indices.length; ++i)
{
result += values[i] * other.values[indices[i]];
}
return result;
}
@Override
final public Iterator iterator()
{
this.compress();
return new EntryIterator();
}
@Override
final public int getDimensionality()
{
return dimensionality;
}
/**
* Helper that checks that i is within the bounds of this array. Throws an
* ArrayIndexOutOfBoundsException if not in bounds
*
* @param i The index to check
* @throws ArrayIndexOutOfBoundsException if i not in bounds
*/
private void checkBounds(
final int i)
{
if ((i < 0) || (i >= dimensionality))
{
throw new ArrayIndexOutOfBoundsException("Input index " + i
+ " is out of bounds for vectors of length " + dimensionality);
}
}
@Override
public double get(
final int index)
{
checkBounds(index);
if (isCompressed())
{
int low = 0;
int high = indices.length - 1;
while (low <= high)
{
int mid = (int) Math.round((low + high) * .5);
if (indices[mid] == index)
{
return values[mid];
}
else if (indices[mid] < index)
{
low = mid + 1;
}
else // if (locs[mid] > index)
{
high = mid - 1;
}
}
// It's not found cuz it's not in there!
return 0;
}
else
{
MutableDouble v = elements.get(index);
return (v == null) ? 0 : v.value;
}
}
@Override
final public double getElement(
final int index)
{
return this.get(index);
}
@Override
public void set(
final int index,
final double value)
{
setElement(index, value);
}
@Override
final public void setElement(
final int index,
final double value)
{
if (this.isCompressed())
{
// If we're in compressed mode and this matches an existing index,
// then we can just update the array value.
final int i = Arrays.binarySearch(this.indices, index);
if (i >= 0)
{
// Found the index in the array, so update the value.
this.values[i] = value;
return;
}
// else - No entry found. Go through to normal modification mode.
}
decompress();
checkBounds(index);
if (value == 0.0)
{
// Remove zeros. If it is not there, then this will be a no-op.
this.elements.remove(index);
}
else
{
// See if there is already an entry for this value.
MutableDouble entry = this.elements.get(index);
if (entry != null)
{
// Update the value.
entry.value = value;
}
else
{
// Make a new entry for the value.
this.elements.put(index, new MutableDouble(value));
}
}
}
@Override
final public Vector subVector(
final int minIndex,
final int maxIndex)
{
if (minIndex > maxIndex)
{
throw new NegativeArraySizeException("Input bounds [" + minIndex
+ ", " + maxIndex + "] goes backwards!");
}
if (minIndex < 0 || minIndex > maxIndex || maxIndex > dimensionality)
{
throw new ArrayIndexOutOfBoundsException("Input bounds for sub-"
+ "vector [" + minIndex + ", " + maxIndex
+ "] is not within supported bounds [0, " + dimensionality + ")");
}
compress();
SparseVector result = new SparseVector(maxIndex - minIndex + 1);
for (int i = 0; i < indices.length; ++i)
{
if ((indices[i] >= minIndex) && (indices[i] <= maxIndex))
{
result.elements.put(indices[i] - minIndex, new MutableDouble(values[i]));
}
}
return result;
}
/**
* Package-private helper that returns the compressed values. NOTE: If this
* isn't compressed before this method is called, this method returns null
* (it does not ensure this is compressed for optimization).
*
* @return the compressed values
*/
final double[] getValues()
{
return values;
}
/**
* Package-private helper that returns the compressed locations. NOTE: If
* this isn't compressed before this method is called, this method returns
* null (it does not ensure this is compressed for optimization).
*
* @return the compressed locations
*/
final int[] getIndices()
{
return indices;
}
@Override
public int countNonZeros()
{
if (isCompressed())
{
int nnz = 0;
for (double v : values)
{
if (v != 0.0)
{
++nnz;
}
}
return nnz;
}
else
{
return elements.size();
}
}
@Override
final public Vector scale(
final double d)
{
compress();
SparseVector result = new SparseVector(this);
for (int i = 0; i < result.values.length; ++i)
{
result.values[i] *= d;
}
return result;
}
/**
* Package-private helper that clears the contents of this vector
*/
final void clear()
{
if (isCompressed())
{
values = null;
indices = null;
}
elements.clear();
}
@Override
public boolean isSparse()
{
return true;
}
@Override
public VectorFactory getVectorFactory()
{
return CustomSparseVectorFactory.INSTANCE;
}
@Override
public double sum()
{
this.compress();
double result = 0.0;
for (final double value : this.values)
{
result += value;
}
return result;
}
@Override
public double getMinValue()
{
this.compress();
double min = this.getEntryCount() < this.getDimensionality() ? 0.0 :
Double.POSITIVE_INFINITY;
for (final double value : this.values)
{
if (value < min)
{
min = value;
}
}
return min;
}
@Override
public double getMaxValue()
{
this.compress();
double max = this.getEntryCount() < this.getDimensionality() ? 0.0 :
Double.NEGATIVE_INFINITY;
for (final double value : this.values)
{
if (value > max)
{
max = value;
}
}
return max;
}
@Override
public int getEntryCount()
{
this.compress();
return this.values.length;
}
/**
* Implements an iterator over sparse entries in this vector.
*/
private class EntryIterator
extends Object
implements Iterator
{
/** Index of current element in iterator. */
private int offset;
/**
* Creates a new {@link EntryIterator}.
*/
public EntryIterator()
{
super();
this.offset = 0;
}
@Override
public boolean hasNext()
{
this.assertNoModification();
return indices != null && this.offset < indices.length;
}
@Override
public VectorEntry next()
{
this.assertNoModification();
final VectorEntry result = new Entry(this.offset);
this.offset++;
return result;
}
/**
* Asserts that no (bad) modifications have been made since the
* iterator started.
*/
private void assertNoModification()
{
if (!elements.isEmpty())
{
throw new ConcurrentModificationException();
}
}
}
/**
* Represents an entry in the sparse vector. Used by the
* {@link EntryIterator}.
*/
class Entry
extends Object
implements VectorEntry
{
/** The 0-based offset in the compressed representation. */
private int offset;
/**
* Creates a new {@link Entry}/
*
* @param offset The 0-based offset in the compressed representation.
*/
public Entry(
final int offset)
{
super();
this.offset = offset;
}
@Override
public int getIndex()
{
return indices[offset];
}
@Override
public void setIndex(
final int index)
{
throw new UnsupportedOperationException("Not supported.");
}
@Override
public double getValue()
{
return values[offset];
}
@Override
public void setValue(
final double value)
{
values[offset] = value;
}
}
}
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