/*
* Copyright (C) 2014 Indeed Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the
* License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied. See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.indeed.imhotep.metrics;
import com.google.common.primitives.Longs;
import com.indeed.flamdex.api.IntValueLookup;
import com.indeed.imhotep.MemoryReserver;
import com.indeed.imhotep.api.ImhotepOutOfMemoryException;
/**
* A precomputed, cached version of an arbitrary metric
* @author dwahler
*/
public class CachedMetric implements IntValueLookup {
private final MemoryReserver memory;
private long[] values;
private long min, max;
public CachedMetric(IntValueLookup original, int numDocs, MemoryReserver memory) throws ImhotepOutOfMemoryException {
this.memory = memory;
if (!memory.claimMemory(numDocs * 8L)) {
throw new ImhotepOutOfMemoryException();
}
this.values = new long[numDocs];
fillValues(original);
}
private void fillValues(IntValueLookup original) {
final int BUFFER_SIZE = 8192;
final int[] idBuffer = new int[BUFFER_SIZE];
final long[] valBuffer = new long[BUFFER_SIZE];
for (int start = 0; start < values.length; start += BUFFER_SIZE) {
final int end = Math.min(values.length, start+BUFFER_SIZE), n = end-start;
for (int i = 0; i < n; i++) {
idBuffer[i] = start + i;
}
original.lookup(idBuffer, valBuffer, n);
System.arraycopy(valBuffer, 0, values, start, n);
}
min = Longs.min(values);
max = Longs.max(values);
}
@Override
public long getMin() {
return min;
}
@Override
public long getMax() {
return max;
}
@Override
public void lookup(int[] docIds, long[] values, int n) {
for (int i = 0; i < n; i++) {
values[i] = this.values[docIds[i]];
}
}
@Override
public long memoryUsed() {
return 8L * values.length;
}
@Override
public void close() {
final long bytesToFree = memoryUsed();
values = null;
memory.releaseMemory(bytesToFree);
}
}