emkornfield commented on a change in pull request #3966: URL: https://github.com/apache/iceberg/pull/3966#discussion_r800711855
########## File path: core/src/test/java/org/apache/iceberg/util/TestZOrderByteUtil.java ########## @@ -0,0 +1,260 @@ +/* + * 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.iceberg.util; + +import java.util.Arrays; +import java.util.Random; +import org.apache.iceberg.relocated.com.google.common.primitives.UnsignedBytes; +import org.apache.iceberg.types.Types; +import org.junit.Assert; +import org.junit.Test; + +public class TestZOrderByteUtil { + private static final byte IIIIIIII = (byte) 255; + private static final byte IOIOIOIO = (byte) 170; + private static final byte OIOIOIOI = (byte) 85; + private static final byte OOOOIIII = (byte) 15; + private static final byte OOOOOOOI = (byte) 1; + private static final byte OOOOOOOO = (byte) 0; + + private static final int NUM_TESTS = 100000; + + private final Random random = new Random(42); + + private String bytesToString(byte[] bytes) { + StringBuilder result = new StringBuilder(); + for (byte b : bytes) { + result.append(String.format("%8s", Integer.toBinaryString(b & 0xFF)).replace(' ', '0')); + } + return result.toString(); + } + + /** + * Returns a non-0 length byte array + */ + private byte[] generateRandomBytes() { + int length = Math.abs(random.nextInt(100) + 1); + byte[] result = new byte[length]; + random.nextBytes(result); + return result; + } + + /** + * Test method to ensure correctness of byte interleaving code + */ + private String interleaveStrings(String[] strings) { + StringBuilder result = new StringBuilder(); + int totalLength = Arrays.stream(strings).mapToInt(String::length).sum(); + int substringIndex = 0; + int characterIndex = 0; + while (characterIndex < totalLength) { + for (String str : strings) { + if (substringIndex < str.length()) { + result.append(str.charAt(substringIndex)); + characterIndex++; + } + } + substringIndex++; + } + return result.toString(); + } + + /** + * Compares the result of a string based interleaving algorithm implemented above + * versus the binary bit-shifting algorithm used in ZOrderByteUtils. Either both + * algorithms are identically wrong or are both identically correct. + */ + @Test + public void testInterleaveRandomExamples() { + for (int test = 0; test < NUM_TESTS; test++) { + int numByteArrays = Math.abs(random.nextInt(6)) + 1; + byte[][] testBytes = new byte[numByteArrays][]; + String[] testStrings = new String[numByteArrays]; + for (int byteIndex = 0; byteIndex < numByteArrays; byteIndex++) { + testBytes[byteIndex] = generateRandomBytes(); + testStrings[byteIndex] = bytesToString(testBytes[byteIndex]); + } + byte[] byteResult = ZOrderByteUtils.interleaveBits(testBytes); + String byteResultAsString = bytesToString(byteResult); + + String stringResult = interleaveStrings(testStrings); + + Assert.assertEquals("String interleave didn't match byte interleave", stringResult, byteResultAsString); + } + } + + @Test + public void testInterleaveEmptyBits() { + byte[][] test = new byte[4][10]; + byte[] expected = new byte[40]; + + Assert.assertArrayEquals("Should combine empty arrays", + expected, ZOrderByteUtils.interleaveBits(test)); + } + + @Test + public void testInterleaveFullBits() { + byte[][] test = new byte[4][]; + test[0] = new byte[]{IIIIIIII, IIIIIIII}; + test[1] = new byte[]{IIIIIIII}; + test[2] = new byte[0]; + test[3] = new byte[]{IIIIIIII, IIIIIIII, IIIIIIII}; + byte[] expected = new byte[]{IIIIIIII, IIIIIIII, IIIIIIII, IIIIIIII, IIIIIIII, IIIIIIII}; + + Assert.assertArrayEquals("Should combine full arrays", + expected, ZOrderByteUtils.interleaveBits(test)); + } + + @Test + public void testInterleaveMixedBits() { Review comment: Thinking about this some more, I think the padding (casting to highest bit-width) is the right thing to do (below are tables showing 1 x 2 bit examples (I think what @rdblue meant by useful vs not-useful can be seen by following). The top and outer left most columns represent the input numbers Existing: | bits: n2_0, n1_1, n1_0 |*0* | *1* | *2* | *3* |-|-|-|-|-| |0|0|1|2|3| |1|4|5|6|7| With padding: | n2_1, n1_1, n2_0, n1_0 |0 | 1 | 2 | 3 |-|-|-|-|-| |0|0|1|4|5| |1 (padded as `0b01`)|2|3|6|7| -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
