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From: liancheng <git@git.apache.org>
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Subject: [GitHub] spark pull request: [SPARK-12936][SQL] Initial bloom filter
 implem...
Content-Type: text/plain
Message-Id: <20160125215652.D1DCCE00DC@git1-us-west.apache.org>
Date: Mon, 25 Jan 2016 21:56:52 +0000 (UTC)

Github user liancheng commented on a diff in the pull request:

    https://github.com/apache/spark/pull/10883#discussion_r50762695
  
    --- Diff: common/sketch/src/main/java/org/apache/spark/util/sketch/BitArray.java ---
    @@ -0,0 +1,94 @@
    +/*
    + * 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.spark.util.sketch;
    +
    +import java.util.Arrays;
    +
    +public final class BitArray {
    +  private final long[] data;
    +  private long bitCount;
    +
    +  static int numWords(long numBits) {
    +    long numWords = (long) Math.ceil(numBits / 64.0);
    +    if (numWords > Integer.MAX_VALUE) {
    +      throw new IllegalArgumentException("Can't allocate enough space for " + numBits + " bits");
    +    }
    +    return (int) numWords;
    +  }
    +
    +  BitArray(long numBits) {
    +    if (numBits <= 0) {
    +      throw new IllegalArgumentException("numBits must be positive");
    +    }
    +    this.data = new long[numWords(numBits)];
    +    long bitCount = 0;
    +    for (long value : data) {
    +      bitCount += Long.bitCount(value);
    +    }
    +    this.bitCount = bitCount;
    +  }
    +
    +  /** Returns true if the bit changed value. */
    +  boolean set(long index) {
    --- End diff --
    
    Should we rename this to `isSetAt`? I found `set` quite ambiguous. At first I thought it "sets" the bit at `index` to 1.


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