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///////////////////////////////////////////////////////////////////////////////////////////////////
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// Copyright 2023 Leszek Koltunski //
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// //
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// This file is part of Magic Cube. //
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// //
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// Magic Cube is proprietary software licensed under an EULA which you should have received //
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// along with the code. If not, check https://distorted.org/magic/License-Magic-Cube.html //
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///////////////////////////////////////////////////////////////////////////////////////////////////
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package org.distorted.objectlib.tablebases;
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///////////////////////////////////////////////////////////////////////////////////////////////////
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class PruningTable
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{
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private static final int HEADER_SIZE = 5;
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private final byte[] mData;
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private final int mNumBits;
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private final int mBucketBytes;
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private final int mTotalSize;
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private final int mNumBuckets;
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private final int mLevel;
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///////////////////////////////////////////////////////////////////////////////////////////////////
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private static String printByte(byte b)
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{
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return String.format("%8s", Integer.toBinaryString(b & 0xFF)).replace(' ', '0');
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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private int numBytesForIndices(int total)
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{
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int bytes = 0;
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while(total!=0)
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{
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total>>=8;
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bytes++;
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}
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return bytes;
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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private void writeHeader()
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{
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mData[0] = (byte)mLevel;
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mData[1] = (byte)mBucketBytes;
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mData[2] = (byte)mNumBits;
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mData[3] = (byte)(mNumBuckets/256);
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mData[4] = (byte)(mNumBuckets%256);
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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private int getBucketOffset(int bucket)
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{
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if( bucket>=mNumBuckets ) return mTotalSize;
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int ret = 0;
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int start = HEADER_SIZE + bucket*mBucketBytes;
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for(int i=0; i<mBucketBytes; i++)
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{
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ret<<=8;
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ret += ( ((int)(mData[start+i]))&0xff);
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}
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return HEADER_SIZE+mNumBuckets*mBucketBytes+ret;
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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private void writeBucketPointers(int[] bucket)
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{
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int start=HEADER_SIZE;
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for( int b : bucket )
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{
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for( int i=0; i<mBucketBytes; i++)
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{
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mData[start+mBucketBytes-1-i] = (byte)(b%256);
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b>>=8;
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}
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start += mBucketBytes;
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}
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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private int retrieveData(int index, int entryInBucket)
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{
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int bits = entryInBucket*mNumBits;
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int bytes = index + bits/8;
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int ret=0;
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switch(mNumBits)
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{
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case 4: ret = (bits%8)!=0 ? (mData[bytes]&0xf) : ((mData[bytes]>>>4)&0xf);
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break;
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case 8: ret = (mData[bytes]&0xff);
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break;
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case 12: ret = (bits%8)!=0 ? ((mData[bytes]&0xf)*256 + (mData[bytes+1]&0xff)) : ( (mData[bytes]&0xff)*16 + ((mData[bytes+1]>>>4)&0xf));
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break;
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case 16: ret = (mData[bytes]&0xff)*256 + (mData[bytes+1]&0xff);
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break;
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}
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return ret;
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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private void insertData(int index, int entryInBucket, int value)
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{
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int bits = entryInBucket*mNumBits;
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int bytes = index + bits/8;
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switch(mNumBits)
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{
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case 4: if( (bits%8) !=0 ) mData[bytes] = (byte)((mData[bytes]&(~0xf)) + value );
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else mData[bytes] = (byte)((value<<4) + (mData[bytes]&0xf));
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break;
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case 8: mData[bytes] = (byte)value;
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break;
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case 12: if( (bits%8) !=0 )
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{
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mData[bytes] = (byte)((mData[bytes]&(~0xf)) + (value>>>8));
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mData[bytes+1]= (byte)value;
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}
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else
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{
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mData[bytes] = (byte)(value>>>4);
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mData[bytes+1]= (byte)((byte)(value<<4) + (mData[bytes+1]&( 0xf)));
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}
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break;
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case 16: mData[bytes] = (byte)(value>>>8);
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mData[bytes+1] = (byte)(value&(0xff));
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}
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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private void writeBuckets(Tablebase table)
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{
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int mask = (1<<mNumBits);
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int prevBucket = -1;
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int entryInBucket = 0;
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int index = 0;
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int size = table.getSize();
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for(int i=0; i<size; i++)
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if( table.retrieveUnpacked(i)==mLevel )
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{
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int toBeWritten = (i%mask);
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int currBucket = (i>>mNumBits);
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if( currBucket!=prevBucket )
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{
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index = getBucketOffset(currBucket);
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entryInBucket = 0;
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}
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else
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{
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entryInBucket ++;
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}
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prevBucket = currBucket;
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insertData(index,entryInBucket,toBeWritten);
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}
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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// PUBLIC API
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///////////////////////////////////////////////////////////////////////////////////////////////////
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// only numBits = 4,8,12,16 actually supported
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public PruningTable(Tablebase table, int level, int numBits)
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{
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mNumBits = numBits;
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mLevel = level;
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int size = table.getSize();
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int entrySize = (1<<numBits);
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mNumBuckets = (size+entrySize-1)/entrySize;
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int[] bucket = new int[mNumBuckets];
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for(int i=0; i<size; i++)
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if( table.retrieveUnpacked(i)==level )
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{
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int currBucket = i/entrySize;
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bucket[currBucket]++;
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}
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int totalBytesForTable = 0;
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for(int i=0; i<mNumBuckets; i++)
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{
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int numBytes = (bucket[i]*numBits+7)/8;
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bucket[i] = totalBytesForTable;
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totalBytesForTable+=numBytes;
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}
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mBucketBytes = numBytesForIndices(totalBytesForTable);
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int totalBytesForBuckets = mNumBuckets*mBucketBytes;
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mTotalSize = HEADER_SIZE + totalBytesForBuckets + totalBytesForTable;
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mData = new byte[mTotalSize];
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writeHeader();
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writeBucketPointers(bucket);
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writeBuckets(table);
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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public boolean belongs(int number)
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{
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int bucket = (number>>mNumBits);
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int offset1 = getBucketOffset(bucket);
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int offset2 = getBucketOffset(bucket+1);
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int numBytesInBucket = offset2-offset1;
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int numEntriesInBucket = (8*numBytesInBucket)/mNumBits;
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if( mNumBits==4 && numBytesInBucket>0 )
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{
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byte val = mData[offset2-1];
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if( (val/16)*16 == val ) numEntriesInBucket--;
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}
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int lower = 0;
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int upper = numEntriesInBucket-1;
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while( upper>=lower )
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{
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int mid = (lower+upper)/2;
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int value = retrieveData(offset1,mid);
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value += (bucket<<mNumBits);
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if( value==number ) return true;
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if( value>number ) upper = mid-1;
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else lower = mid+1;
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}
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return false;
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}
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}
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