Merge pull request #551 from vfunshteyn/master

[core] Generator refactoring

core/src/main/java/com/yahoo/ycsb/generator/AcknowledgedCounterGenerator.java

@@ -50,7 +50,7 @@ public AcknowledgedCounterGenerator(int countstart)
 	 * (as opposed to the highest generated counter value).
 	 */
 	@Override
-	public int lastInt()
+	public Integer lastValue()
 	{
 		return limit;
 	}

core/src/main/java/com/yahoo/ycsb/generator/ConstantIntegerGenerator.java

@@ -22,7 +22,7 @@
  * @author sears
  *
  */
-public class ConstantIntegerGenerator extends IntegerGenerator {
+public class ConstantIntegerGenerator extends NumberGenerator {
 	private final int i;
 	/**
 	 * @param i The integer that this generator will always return.
@@ -32,7 +32,7 @@ public ConstantIntegerGenerator(int i) {
 	}
 
 	@Override
-	public int nextInt() {
+	public Integer nextValue() {
 		return i;
 	}
 

core/src/main/java/com/yahoo/ycsb/generator/CounterGenerator.java

@@ -22,33 +22,28 @@
 /**
  * Generates a sequence of integers 0, 1, ...
  */
-public class CounterGenerator extends IntegerGenerator
+public class CounterGenerator extends NumberGenerator
 {
-	final AtomicInteger counter;
+	private final AtomicInteger counter;
 
 	/**
 	 * Create a counter that starts at countstart
 	 */
 	public CounterGenerator(int countstart)
 	{
 		counter=new AtomicInteger(countstart);
-		setLastInt(counter.get()-1);
 	}
 
-	/**
-	 * If the generator returns numeric (integer) values, return the next value as an int. Default is to return -1, which
-	 * is appropriate for generators that do not return numeric values.
-	 */
-	public int nextInt() 
+	@Override
+  public Integer nextValue() 
 	{
-		int ret = counter.getAndIncrement();
-		setLastInt(ret);
-		return ret;
+		return counter.getAndIncrement();
 	}
+
 	@Override
-	public int lastInt()
+	public Integer lastValue()
 	{
-	                return counter.get() - 1;
+	    return counter.get() - 1;
 	}
 	@Override
 	public double mean() {

core/src/main/java/com/yahoo/ycsb/generator/DiscreteGenerator.java

@@ -17,42 +17,42 @@
 
 package com.yahoo.ycsb.generator;
 
-import java.util.Vector;
-import java.util.Random;
+import java.util.ArrayList;
+import java.util.Collection;
+import static java.util.Objects.requireNonNull;
 
 import com.yahoo.ycsb.Utils;
-import com.yahoo.ycsb.WorkloadException;
 
 /**
  * Generates a distribution by choosing from a discrete set of values.
  */
-public class DiscreteGenerator extends Generator
+public class DiscreteGenerator extends Generator<String>
 {
-	class Pair
+	private static class Pair
 	{
-		public double _weight;
-		public String _value;
+		private double _weight;
+		private String _value;
 
 		Pair(double weight, String value)
 		{
 			_weight=weight;
-			_value=value;
+			_value = requireNonNull(value);
 		}
 	}
 
-	Vector<Pair> _values;
-	String _lastvalue;
+	private final Collection<Pair> _values = new ArrayList<>();
+	private String _lastvalue;
 
 	public DiscreteGenerator()
 	{
-		_values=new Vector<Pair>();
 		_lastvalue=null;
 	}
 
 	/**
 	 * Generate the next string in the distribution.
 	 */
-	public String nextString()
+	@Override
+    public String nextValue()
 	{
 		double sum=0;
 
@@ -65,43 +65,30 @@ public String nextString()
 
 		for (Pair p : _values)
 		{
-			if (val<p._weight/sum)
+		    double pw = p._weight / sum;
+			if (val < pw)
 			{
 				return p._value;
 			}
 
-			val-=p._weight/sum;
+			val -= pw;
 		}
 
-		//should never get here.
-		System.out.println("oops. should not get here.");
+		throw new AssertionError("oops. should not get here.");
 
-		System.exit(0);
-
-		return null;
-	}
-
-	/**
-	 * If the generator returns numeric (integer) values, return the next value as an int. Default is to return -1, which
-	 * is appropriate for generators that do not return numeric values.
-	 * 
-	 * @throws WorkloadException if this generator does not support integer values
-	 */
-	public int nextInt() throws WorkloadException
-	{
-		throw new WorkloadException("DiscreteGenerator does not support nextInt()");
 	}
 
 	/**
 	 * Return the previous string generated by the distribution; e.g., returned from the last nextString() call. 
 	 * Calling lastString() should not advance the distribution or have any side effects. If nextString() has not yet 
 	 * been called, lastString() should return something reasonable.
 	 */
-	public String lastString()
+	@Override
+    public String lastValue()
 	{
 		if (_lastvalue==null)
 		{
-			_lastvalue=nextString();
+			_lastvalue=nextValue();
 		}
 		return _lastvalue;
 	}

core/src/main/java/com/yahoo/ycsb/generator/ExponentialGenerator.java

@@ -17,20 +17,18 @@
 
 package com.yahoo.ycsb.generator;
 
-import java.util.Random;
-
 import com.yahoo.ycsb.Utils;
 
 /**
  * A generator of an exponential distribution. It produces a sequence
- * of time intervals (integers) according to an exponential
+ * of time intervals according to an exponential
  * distribution.  Smaller intervals are more frequent than larger
  * ones, and there is no bound on the length of an interval.  When you
  * construct an instance of this class, you specify a parameter gamma,
  * which corresponds to the rate at which events occur.
  * Alternatively, 1/gamma is the average length of an interval.
  */
-public class ExponentialGenerator extends IntegerGenerator
+public class ExponentialGenerator extends NumberGenerator
 {
     // What percentage of the readings should be within the most recent exponential.frac portion of the dataset?
     public static final String EXPONENTIAL_PERCENTILE_PROPERTY="exponential.percentile";
@@ -43,7 +41,7 @@ public class ExponentialGenerator extends IntegerGenerator
 	/**
 	 * The exponential constant to use.
 	 */
-	double _gamma;	
+	private double _gamma;	
 
 	/******************************* Constructors **************************************/
 
@@ -62,27 +60,16 @@ public ExponentialGenerator(double percentile, double range)
 
 	/****************************************************************************************/
 
-	/** 
-	 * Generate the next item. this distribution will be skewed toward lower integers; e.g. 0 will
-	 * be the most popular, 1 the next most popular, etc.
-	 * @param itemcount The number of items in the distribution.
-	 * @return The next item in the sequence.
-	 */
-	@Override
-	public int nextInt()
-	{
-		return (int)nextLong();
-	}
 
 	/**
-	 * Generate the next item as a long.
-	 * 
-	 * @param itemcount The number of items in the distribution.
-	 * @return The next item in the sequence.
-	 */
-	public long nextLong()
+	 * Generate the next item as a long. This distribution will be skewed toward lower values; e.g. 0 will
+     * be the most popular, 1 the next most popular, etc.
+     * @return The next item in the sequence.
+     */
+	@Override
+    public Double nextValue()
 	{
-		return (long) (-Math.log(Utils.random().nextDouble()) / _gamma);
+		return -Math.log(Utils.random().nextDouble()) / _gamma;
 	}
 
 	@Override
@@ -93,7 +80,7 @@ public static void main(String args[]) {
         ExponentialGenerator e = new ExponentialGenerator(90, 100);
         int j = 0;
         for(int i = 0; i < 1000; i++) {
-            if(e.nextInt() < 100) {
+            if(e.nextValue() < 100) {
                 j++;
             }
         }

core/src/main/java/com/yahoo/ycsb/generator/FileGenerator.java

@@ -15,74 +15,61 @@
 
 package com.yahoo.ycsb.generator;
 
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.InputStreamReader;
+import java.io.FileReader;
 import java.io.BufferedReader;
 import java.io.IOException;
+import java.io.Reader;
 
 /**
  * A generator, whose sequence is the lines of a file.
  */
-public class FileGenerator extends Generator
+public class FileGenerator extends Generator<String>
 {
-	String filename;
-	String current;
-	BufferedReader reader;
+	private final String filename;
+	private String current;
+	private BufferedReader reader;
 
 	/**
 	 * Create a FileGenerator with the given file.
 	 * @param _filename The file to read lines from.
 	 */
-	public FileGenerator(String _filename)
+	public FileGenerator(String _filename) 
 	{
-		try {
-			filename = _filename;
-			File file = new File(filename);
-			FileInputStream in = new FileInputStream(file);
-			reader = new BufferedReader(new InputStreamReader(in));
-		} catch(IOException e) {
-			System.err.println("Exception: " + e);
-		}
+	  filename = _filename;
+	  reloadFile();
 	}
 
 	/**
 	 * Return the next string of the sequence, ie the next line of the file.
 	 */
-	public synchronized String nextString()
+	@Override
+  public synchronized String nextValue()
 	{
 		try {
 			return current = reader.readLine();
-		} catch(NullPointerException e) {
-			System.err.println("NullPointerException: " + filename + ':' + current);
-			throw e;
 		} catch(IOException e) {
-			System.err.println("Exception: " + e);
-			return null;
+		  throw new RuntimeException(e);		
 		}
 	}
 
 	/**
 	 * Return the previous read line.
 	 */
-	public String lastString()
+	@Override
+  public String lastValue()
 	{
 		return current;
 	}
 
 	/**
 	 * Reopen the file to reuse values.
 	 */
-	public synchronized void reloadFile()
-	{
-		try {
+	public synchronized void reloadFile() {
+	  try (Reader r = reader) {
 			System.err.println("Reload " + filename);
-			reader.close();
-			File file = new File(filename);
-			FileInputStream in = new FileInputStream(file);
-			reader = new BufferedReader(new InputStreamReader(in));
-		} catch(IOException e) {
-			System.err.println("Exception: " + e);
-		}
+			reader = new BufferedReader(new FileReader(filename));
+	  } catch (IOException e) {
+	    throw new RuntimeException(e);
+	  }
 	}
 }

core/src/main/java/com/yahoo/ycsb/generator/Generator.java

@@ -18,20 +18,30 @@
 package com.yahoo.ycsb.generator;
 
 /**
- * An expression that generates a sequence of string values, following some distribution (Uniform, Zipfian, Sequential, etc.)
+ * An expression that generates a sequence of values, following some distribution (Uniform, Zipfian, Sequential, etc.)
  */
-public abstract class Generator 
+public abstract class Generator<V> 
 {
 	/**
-	 * Generate the next string in the distribution.
+	 * Generate the next value in the distribution.
 	 */
-	public abstract String nextString();
+	public abstract V nextValue();
 
 	/**
-	 * Return the previous string generated by the distribution; e.g., returned from the last nextString() call. 
-	 * Calling lastString() should not advance the distribution or have any side effects. If nextString() has not yet 
-	 * been called, lastString() should return something reasonable.
+	 * Return the previous value generated by the distribution; e.g., returned from the last {@link Generator#nextValue()} call. 
+	 * Calling {@link #lastValue()} should not advance the distribution or have any side effects. If {@link #nextValue()} has not yet 
+	 * been called, {@link #lastValue()} should return something reasonable.
 	 */
-	public abstract String lastString();
+	public abstract V lastValue();
+
+	public final String nextString() {
+	  V ret = nextValue();
+	  return ret == null ? null : ret.toString();
+	}
+
+	public final String lastString() {
+	  V ret = lastValue();
+	  return ret == null ? null : ret.toString();
+	}
 }