com.yahoo.sketches.cpc.CpcUtil Maven / Gradle / Ivy
/*
* Copyright 2018, Yahoo! Inc. Licensed under the terms of the
* Apache License 2.0. See LICENSE file at the project root for terms.
*/
package com.yahoo.sketches.cpc;
import java.util.Arrays;
import com.yahoo.sketches.SketchesArgumentException;
/**
* @author Lee Rhodes
* @author Kevin Lang
*/
final class CpcUtil {
static final int minLgK = 4;
static final int maxLgK = 26;
static void checkLgK(final int lgK) {
if ((lgK < minLgK) || (lgK > maxLgK)) {
throw new SketchesArgumentException("LgK must be >= 4 and <= 26: " + lgK);
}
}
static Flavor determineFlavor(final int lgK, final long numCoupons) {
final long c = numCoupons;
final long k = 1L << lgK;
final long c2 = c << 1;
final long c8 = c << 3;
final long c32 = c << 5;
if (c == 0) {
return Flavor.EMPTY; // 0 == C < 1
}
if (c32 < (3 * k)) {
return Flavor.SPARSE; // 1 <= C < 3K/32
}
if (c2 < k) {
return Flavor.HYBRID; // 3K/32 <= C < K/2
}
if (c8 < (27 * k)) {
return Flavor.PINNED; // K/2 <= C < 27K/8
}
else {
return Flavor.SLIDING; // 27K/8 <= C
}
}
/**
* Warning: this is called in several places, including during the
* transitional moments during which sketch invariants involving
* flavor and offset are out of whack and in fact we are re-imposing
* them. Therefore it cannot rely on determineFlavor() or
* determineCorrectOffset(). Instead it interprets the low level data
* structures "as is".
*
* This produces a full-size k-by-64 bit matrix from any Live sketch.
*
* @param sketch the given sketch
* @return the bit matrix as an array of longs.
*/
static long[] bitMatrixOfSketch(final CpcSketch sketch) {
final int k = (1 << sketch.lgK);
final int offset = sketch.windowOffset;
assert (offset >= 0) && (offset <= 56);
final long[] matrix = new long[k];
if (sketch.numCoupons == 0) {
return matrix; // Returning a matrix of zeros rather than NULL.
}
//Fill the matrix with default rows in which the "early zone" is filled with ones.
//This is essential for the routine's O(k) time cost (as opposed to O(C)).
final long defaultRow = (1L << offset) - 1L;
Arrays.fill(matrix, defaultRow);
final byte[] window = sketch.slidingWindow;
if (window != null) { // In other words, we are in window mode, not sparse mode.
for (int i = 0; i < k; i++) { // set the window bits, trusting the sketch's current offset.
matrix[i] |= ((window[i] & 0XFFL) << offset);
}
}
final PairTable table = sketch.pairTable;
assert (table != null);
final int[] slots = table.getSlotsArr();
final int numSlots = 1 << table.getLgSizeInts();
for (int i = 0; i < numSlots; i++) {
final int rowCol = slots[i];
if (rowCol != -1) {
final int col = rowCol & 63;
final int row = rowCol >>> 6;
// Flip the specified matrix bit from its default value.
// In the "early" zone the bit changes from 1 to 0.
// In the "late" zone the bit changes from 0 to 1.
matrix[row] ^= (1L << col);
}
}
return matrix;
}
static long countBitsSetInMatrix(final long[] matrix) {
long count = 0;
final int len = matrix.length;
for (int i = 0; i < len; i++) { count += Long.bitCount(matrix[i]); }
return count;
}
static int determineCorrectOffset(final int lgK, final long numCoupons) {
final long c = numCoupons;
final long k = (1L << lgK);
final long tmp = (c << 3) - (19L * k); // 8C - 19K
if (tmp < 0) { return 0; }
return (int) (tmp >>> (lgK + 3)); // tmp / 8K
}
}