slow-J commented on code in PR #12741: URL: https://github.com/apache/lucene/pull/12741#discussion_r1378112509
########## lucene/core/src/java/org/apache/lucene/codecs/lucene99/PForUtil.java: ########## @@ -0,0 +1,558 @@ +/* + * 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.lucene.codecs.lucene99; + +import java.io.IOException; +import java.util.Arrays; +import org.apache.lucene.store.DataInput; +import org.apache.lucene.store.DataOutput; +import org.apache.lucene.util.LongHeap; +import org.apache.lucene.util.packed.PackedInts; + +/** Utility class to encode sequences of 128 small positive integers. */ +final class PForUtil { + + private static final int MAX_EXCEPTIONS = 7; + private static final int HALF_BLOCK_SIZE = ForUtil.BLOCK_SIZE / 2; + + // IDENTITY_PLUS_ONE[i] == i + 1 + private static final long[] IDENTITY_PLUS_ONE = new long[ForUtil.BLOCK_SIZE]; + + static { + for (int i = 0; i < ForUtil.BLOCK_SIZE; ++i) { + IDENTITY_PLUS_ONE[i] = i + 1; + } + } + + static boolean allEqual(long[] l) { + for (int i = 1; i < ForUtil.BLOCK_SIZE; ++i) { + if (l[i] != l[0]) { + return false; + } + } + return true; + } + + private final ForUtil forUtil; + // buffer for reading exception data; each exception uses two bytes (pos + high-order bits of the + // exception) + private final byte[] exceptionBuff = new byte[MAX_EXCEPTIONS * 2]; + + PForUtil(ForUtil forUtil) { + assert ForUtil.BLOCK_SIZE <= 256 : "blocksize must fit in one byte. got " + ForUtil.BLOCK_SIZE; + this.forUtil = forUtil; + } + + /** Encode 128 integers from {@code longs} into {@code out}. */ + void encode(long[] longs, DataOutput out) throws IOException { + // Determine the top MAX_EXCEPTIONS + 1 values + final LongHeap top = new LongHeap(MAX_EXCEPTIONS + 1); + for (int i = 0; i <= MAX_EXCEPTIONS; ++i) { + top.push(longs[i]); + } + long topValue = top.top(); + for (int i = MAX_EXCEPTIONS + 1; i < ForUtil.BLOCK_SIZE; ++i) { + if (longs[i] > topValue) { + topValue = top.updateTop(longs[i]); + } + } + + long max = 0L; + for (int i = 1; i <= top.size(); ++i) { + max = Math.max(max, top.get(i)); + } + + final int maxBitsRequired = PackedInts.bitsRequired(max); + // We store the patch on a byte, so we can't decrease the number of bits required by more than 8 + final int patchedBitsRequired = + Math.max(PackedInts.bitsRequired(topValue), maxBitsRequired - 8); + int numExceptions = 0; + final long maxUnpatchedValue = (1L << patchedBitsRequired) - 1; + for (int i = 2; i <= top.size(); ++i) { + if (top.get(i) > maxUnpatchedValue) { + numExceptions++; + } + } + final byte[] exceptions = new byte[numExceptions * 2]; + if (numExceptions > 0) { + int exceptionCount = 0; + for (int i = 0; i < ForUtil.BLOCK_SIZE; ++i) { + if (longs[i] > maxUnpatchedValue) { + exceptions[exceptionCount * 2] = (byte) i; + exceptions[exceptionCount * 2 + 1] = (byte) (longs[i] >>> patchedBitsRequired); + longs[i] &= maxUnpatchedValue; + exceptionCount++; + } + } + assert exceptionCount == numExceptions : exceptionCount + " " + numExceptions; + } + + if (allEqual(longs) && maxBitsRequired <= 8) { + for (int i = 0; i < numExceptions; ++i) { + exceptions[2 * i + 1] = + (byte) (Byte.toUnsignedLong(exceptions[2 * i + 1]) << patchedBitsRequired); + } + out.writeByte((byte) (numExceptions << 5)); + out.writeVLong(longs[0]); + } else { + final int token = (numExceptions << 5) | patchedBitsRequired; + out.writeByte((byte) token); + forUtil.encode(longs, patchedBitsRequired, out); + } + out.writeBytes(exceptions, exceptions.length); + } + + /** Decode 128 integers into {@code ints}. */ + void decode(DataInput in, long[] longs) throws IOException { + final int token = Byte.toUnsignedInt(in.readByte()); + final int bitsPerValue = token & 0x1f; + final int numExceptions = token >>> 5; + if (bitsPerValue == 0) { + Arrays.fill(longs, 0, ForUtil.BLOCK_SIZE, in.readVLong()); + } else { + forUtil.decode(bitsPerValue, in, longs); + } + for (int i = 0; i < numExceptions; ++i) { + longs[Byte.toUnsignedInt(in.readByte())] |= + Byte.toUnsignedLong(in.readByte()) << bitsPerValue; + } + } + + /** Decode deltas, compute the prefix sum and add {@code base} to all decoded longs. */ + void decodeAndPrefixSum(DataInput in, long base, long[] longs) throws IOException { Review Comment: Removed in latest commit. -- This is an automated message from the Apache Git Service. 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