siddharthteotia commented on code in PR #12223: URL: https://github.com/apache/pinot/pull/12223#discussion_r1462862679
########## pinot-common/src/test/java/org/apache/pinot/common/utils/FALFInternerTest.java: ########## @@ -0,0 +1,168 @@ +/** + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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 org.apache.pinot.common.utils; + +import com.google.common.collect.Interner; +import com.google.common.collect.Interners; +import java.util.Objects; +import java.util.Random; +import org.apache.pinot.spi.utils.FALFInterner; +import org.testng.Assert; +import org.testng.annotations.Test; + + +public class FALFInternerTest { + @Test + public void testInterningByteBuffers() { + Random random = new Random(1); + + int nUniqueObjs = 1024; + int nTotalObjs = 8 * nUniqueObjs; + + String[] allObjs = new String[nTotalObjs]; + + // Create an array of objects where each object should have ~8 copies + for (int i = 0; i < nTotalObjs; i++) { + int next = random.nextInt(nUniqueObjs); + allObjs[i] = Integer.toString(next); + } + + Interner<String> exactInterner = Interners.newStrongInterner(); + Interner<String> falfInterner = new FALFInterner(nUniqueObjs); + Interner<String> falfInternerCustomHash = new FALFInterner(nUniqueObjs, s -> hashCode((String) s), Objects::equals); + + // Go over all objects and intern them using both exact and FALF interners + int nHits1 = runInterning(allObjs, exactInterner, true); + int nHits2 = runInterning(allObjs, falfInterner, true); + int nHits3 = runInterning(allObjs, falfInternerCustomHash, true); + + System.out.println(nHits1); + System.out.println(nHits2); + System.out.println(nHits3); + + // For the exact interner, we should get a hit for each object except the + // first nUniqueObjs. + Assert.assertEquals(nHits1, nTotalObjs - nUniqueObjs); + + // For the FALF interner, due to its fixed size and thus almost inevitable hash + // collisions, the number of hits is smaller. Let's verify that it's not too small, though. + Assert.assertTrue(nHits2 > (nTotalObjs - nUniqueObjs) * 0.4); + + // With the better hash function, FALF interner should have more hits + Assert.assertTrue(nHits3 > (nTotalObjs - nUniqueObjs) * 0.6); + + // Ad hoc benchmarking code. Disabled to avoid test slowdown. + // In one run the MacBook laptop, FALFInterner below performs nearly twice faster + // (1217 ms vs 2230 ms) With custom hash function, FALFInterner's speed is about the + // same as the Guava interner. +// for (int j = 0; j < 3; j++) { +// long time0 = System.currentTimeMillis(); +// long totNHits = 0; +// for (int i = 0; i < 10000; i++) { +// totNHits += runInterning(allObjs, exactInterner, false); +// } +// long time1 = System.currentTimeMillis(); +// System.out.println("Guava interner. totNHits = " + totNHits + ", time = " + (time1 - time0)); +// +// time0 = System.currentTimeMillis(); +// totNHits = 0; +// for (int i = 0; i < 10000; i++) { +// totNHits += runInterning(allObjs, falfInterner, false); +// } +// time1 = System.currentTimeMillis(); +// System.out.println("FALF interner. totNHits = " + totNHits + ", time = " + (time1 - time0)); +// +// time0 = System.currentTimeMillis(); +// totNHits = 0; +// for (int i = 0; i < 10000; i++) { +// totNHits += runInterning(allObjs, falfInternerCustomHash, false); +// } +// time1 = System.currentTimeMillis(); +// System.out.println("FALF interner Custom Hash. totNHits = " + totNHits + ", time = " + (time1 - time0)); +// } + } + + private int runInterning(String[] objs, Interner<String> interner, boolean performAssert) { + int nHits = 0; + for (String origObj : objs) { + String internedObj = interner.intern(origObj); + if (performAssert) { + Assert.assertEquals(origObj, internedObj); + } + if (origObj != internedObj) { + nHits++; + } + } + return nHits; + } + + // Custom hash code implementation, that gives better distribution than standard hashCode() + + private static final int C1 = 0xcc9e2d51; + private static final int C2 = 0x1b873593; + + public static int hashCode(String s) { + int h1 = 0; + + // step through value 2 chars at a time + for (int i = 1; i < s.length(); i += 2) { + int k1 = s.charAt(i - 1) | (s.charAt(i) << 16); + h1 = nextHashCode(k1, h1); + } + + // deal with any remaining characters + if ((s.length() & 1) == 1) { + int k1 = s.charAt(s.length() - 1); + k1 = mixK1(k1); + h1 ^= k1; + } + + return fmix(h1, s.length() * 2); + } + + private static int nextHashCode(int value, int prevHashCode) { + int k1 = mixK1(value); + return mixH1(prevHashCode, k1); + } + + private static int mixK1(int k1) { + k1 *= C1; + k1 = Integer.rotateLeft(k1, 15); + k1 *= C2; + return k1; + } + + private static int mixH1(int h1, int k1) { + h1 ^= k1; + h1 = Integer.rotateLeft(h1, 13); + h1 = h1 * 5 + 0xe6546b64; + return h1; + } + + private static int fmix(int h1, int len) { + // Force all bits to avalanche + h1 ^= len; + h1 ^= h1 >>> 16; + h1 *= 0x85ebca6b; + h1 ^= h1 >>> 13; + h1 *= 0xc2b2ae35; + h1 ^= h1 >>> 16; + return h1; Review Comment: Shouldn't this be wrapped around in the form of a static helper class and then used in both test and actual code ? -- This is an automated message from the Apache Git Service. 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