| /* |
| * Copyright (C) 2015 Google 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 benchmarks; |
| |
| import java.math.BigInteger; |
| import java.util.Random; |
| |
| /** |
| * This pretends to measure performance of operations on small BigIntegers. |
| * Given our current implementation, this is really a way to measure performance of |
| * finalization and JNI. |
| * We manually determine the number of iterations so that it should cause total memory |
| * allocation on the order of a few hundred megabytes. Due to BigInteger's reliance on |
| * finalization, these may unfortunately all be kept around at once. |
| */ |
| public class SmallBigIntegerBenchmark { |
| // We allocate about 2 1/3 BigIntegers per iteration. |
| // Assuming 100 bytes/BigInteger, this gives us around 500MB total. |
| static final int NITERS = 2 * 1000 * 1000; |
| static final BigInteger BIG_THREE = BigInteger.valueOf(3); |
| static final BigInteger BIG_FOUR = BigInteger.valueOf(4); |
| |
| public static void main(String args[]) { |
| final Random r = new Random(); |
| BigInteger x = new BigInteger(20, r); |
| final long startNanos = System.nanoTime(); |
| long intermediateNanos = 0; |
| for (int i = 0; i < NITERS; ++i) { |
| if (i == NITERS / 100) { |
| intermediateNanos = System.nanoTime(); |
| } |
| // We know this converges, but the compiler doesn't. |
| if (x.and(BigInteger.ONE).equals(BigInteger.ONE)) { |
| x = x.multiply(BIG_THREE).add(BigInteger.ONE); |
| } else { |
| x = x.shiftRight(1); |
| } |
| } |
| if (x.signum() < 0 || x.compareTo(BIG_FOUR) > 0) { |
| throw new AssertionError("Something went horribly wrong."); |
| } |
| final long finalNanos = System.nanoTime(); |
| double firstFewTime = ((double) intermediateNanos - (double) startNanos) / (NITERS / 100); |
| double restTime = ((double) finalNanos - (double) intermediateNanos) / (99 * NITERS / 100); |
| System.out.println("First Few: " + firstFewTime |
| + " nanoseconds per iteration (2.33 BigInteger ops/iter)"); |
| System.out.println("Remainder: " + restTime + " nanoseconds per iteration"); |
| } |
| } |
| |