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package cardinality;
import shared.Parser;
import shared.Tools;
/**
* @author Brian Bushnell
* @date Mar 10, 2020
*
*/
public final class LogLog8_simple extends CardinalityTracker {
/*--------------------------------------------------------------*/
/*---------------- Initialization ----------------*/
/*--------------------------------------------------------------*/
/** Create a LogLog with default parameters */
LogLog8_simple(){
this(2048, 31, -1, 0);
}
/** Create a LogLog with parsed parameters */
LogLog8_simple(Parser p){
super(p);
maxArray=new byte[buckets];
}
/**
* Create a LogLog with specified parameters
* @param buckets_ Number of buckets (counters)
* @param k_ Kmer length
* @param seed Random number generator seed; -1 for a random seed
* @param minProb_ Ignore kmers with under this probability of being correct
*/
LogLog8_simple(int buckets_, int k_, long seed, float minProb_){
super(buckets_, k_, seed, minProb_);
maxArray=new byte[buckets];
}
/*--------------------------------------------------------------*/
/*---------------- Methods ----------------*/
/*--------------------------------------------------------------*/
/** Restores floating point to integer.
* This subclass has no mantissa so only the exponent is restored. */
private long restore(int value){
final int leading=value; //Number of leading zeros
long mantissa=1; //1.xxxx but in this case the X's are all zero
int shift=64-leading-1; //Amount to left shift the mantissa
long original=mantissa<<shift; //Restored original number
return original;
}
@Override
public final long cardinality(){
double sum=0;
int count=0;
for(int i=0; i<maxArray.length; i++){
int max=maxArray[i];
long val=restore(max);
if(max>0 && val>0){
sum+=val;
count++;
}
}
final int subsets=count;//Could be set to count or buckets
final double mean=sum/Tools.max(subsets, 1);
//What to use as the value from the counters
final double proxy=mean;
final double estimatePerSet=2*(Long.MAX_VALUE/proxy);
final double mantissaFactor=0.7213428177;//Empirically derived
final double emptyBucketModifier=((count+buckets)/(float)(buckets+buckets));//Approximate; overestimate
final double total=estimatePerSet*subsets*mantissaFactor*emptyBucketModifier;
long cardinality=(long)(total);
lastCardinality=cardinality;
return cardinality;
}
@Override
public final void add(CardinalityTracker log){
assert(log.getClass()==this.getClass());
add((LogLog8_simple)log);
}
/** @See add(CardinalityTracker) */
public void add(LogLog8_simple log){
if(maxArray!=log.maxArray){
for(int i=0; i<buckets; i++){
maxArray[i]=Tools.max(maxArray[i], log.maxArray[i]);
}
}
}
@Override
public void hashAndStore(final long number){
final long key=Tools.hash64shift(number);
final byte leading=(byte)Long.numberOfLeadingZeros(key);
final int bucket=(int)(key&bucketMask);
maxArray[bucket]=Tools.max(leading, maxArray[bucket]);
}
@Override
public final float[] compensationFactorLogBucketsArray(){
return null;
}
/*--------------------------------------------------------------*/
/*---------------- Fields ----------------*/
/*--------------------------------------------------------------*/
/** Maintains state. These are the actual buckets. */
private final byte[] maxArray;
}
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