rdblue commented on code in PR #3397: URL: https://github.com/apache/parquet-java/pull/3397#discussion_r4098863710
########## parquet-column/src/main/java/org/apache/parquet/column/values/alp/AlpConstants.java: ########## @@ -0,0 +1,80 @@ +/* + * 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.parquet.column.values.alp; + +import org.apache.parquet.Preconditions; + +/** + * Constants for the ALP (Adaptive Lossless floating-Point) encoding. + * + * <p>ALP encoding converts floating-point values to integers using decimal scaling, + * then applies Frame of Reference encoding and bit-packing. + * Values that cannot be losslessly converted are stored as exceptions. + * + * <p>Based on the paper: "ALP: Adaptive Lossless floating-Point Compression" (SIGMOD 2024) + * + * @see <a href="https://dl.acm.org/doi/10.1145/3626717";>ALP Paper</a> + */ +final class AlpConstants { + + private AlpConstants() { + // Utility class + } + + // Page header fields + static final int ALP_COMPRESSION_MODE = 0; + static final int ALP_INTEGER_ENCODING_FOR = 0; + static final int ALP_HEADER_SIZE = 7; + + static final int DEFAULT_VECTOR_SIZE = 1024; + static final int DEFAULT_VECTOR_SIZE_LOG = 10; + + // BytePacker packs/unpacks 8 values at a time (pack8Values/unpack8Values). + static final int PACK_GROUP_SIZE = 8; + + // Capped at 15 (vectorSize=32768) because num_exceptions is uint16, + // so vectorSize must not exceed 65535 to avoid overflow when all values are exceptions. + static final int MAX_LOG_VECTOR_SIZE = 15; + static final int MIN_LOG_VECTOR_SIZE = 3; + + static final int FLOAT_MAX_EXPONENT = 10; + static final int DOUBLE_MAX_EXPONENT = 18; + + // Per-vector metadata sizes in bytes + static final int ALP_INFO_SIZE = 4; // exponent(1) + factor(1) + num_exceptions(2) + static final int FLOAT_FOR_INFO_SIZE = 5; // frame_of_reference(4) + bit_width(1) + static final int DOUBLE_FOR_INFO_SIZE = 9; // frame_of_reference(8) + bit_width(1) + + /** Validates vector size: must be a power of 2 in [2^MIN_LOG .. 2^MAX_LOG]. */ + static int validateVectorSize(int vectorSize) { + Preconditions.checkArgument( + vectorSize > 0 && (vectorSize & (vectorSize - 1)) == 0, Review Comment: This is probably faster, but I think a simpler form would be easier to read and understand, like `Integer.bitCount(vectorSize) == 1` -- 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]
