/**
* Randomly permutes the part of the receiver between <code>from</code> (inclusive) and <code>to
* </code> (inclusive).
*
* @param from the index of the first element (inclusive) to be permuted.
* @param to the index of the last element (inclusive) to be permuted.
* @exception IndexOutOfBoundsException index is out of range ( <tt>size()>0 && (from<0 ||
* from>to || to>=size())</tt> ).
*/
public void shuffleFromTo(int from, int to) {
// overridden for performance only.
if (size == 0) {
return;
}
checkRangeFromTo(from, to, size);
cern.jet.random.Uniform gen =
new cern.jet.random.Uniform(new cern.jet.random.engine.DRand(new java.util.Date()));
short tmpElement;
short[] theElements = elements;
int random;
for (int i = from; i < to; i++) {
random = gen.nextIntFromTo(i, to);
// swap(i, random)
tmpElement = theElements[random];
theElements[random] = theElements[i];
theElements[i] = tmpElement;
}
}
/**
* Uniformly samples (chooses) <tt>n</tt> random elements <i>with or without replacement</i> from
* the contained elements and adds them to the given buffer. If the buffer is connected to a bin,
* the effect is that the chosen elements are added to the bin connected to the buffer. Also see
* {@link #buffered(int) buffered}.
*
* @param n the number of elements to choose.
* @param withReplacement <tt>true</tt> samples with replacement, otherwise samples without
* replacement.
* @param randomGenerator a random number generator. Set this parameter to <tt>null</tt> to use a
* default random number generator seeded with the current time.
* @param buffer the buffer to which chosen elements will be added.
* @throws IllegalArgumentException if <tt>!withReplacement && n > size()</tt>.
* @see cern.jet.random.sampling
*/
public synchronized void sample(
int n,
boolean withReplacement,
RandomEngine randomGenerator,
cern.colt.buffer.DoubleBuffer buffer) {
if (randomGenerator == null) randomGenerator = cern.jet.random.Uniform.makeDefaultGenerator();
buffer.clear();
if (!withReplacement) { // without
if (n > size()) throw new IllegalArgumentException("n must be less than or equal to size()");
cern.jet.random.sampling.RandomSamplingAssistant sampler =
new cern.jet.random.sampling.RandomSamplingAssistant(n, size(), randomGenerator);
for (int i = n; --i >= 0; ) {
if (sampler.sampleNextElement()) buffer.add(this.elements.getQuick(i));
}
} else { // with
cern.jet.random.Uniform uniform = new cern.jet.random.Uniform(randomGenerator);
int s = size();
for (int i = n; --i >= 0; ) {
buffer.add(this.elements.getQuick(uniform.nextIntFromTo(0, s - 1)));
}
buffer.flush();
}
}
@Override
public int nextIntBetween(int min, int max) {
return uniform.nextIntFromTo(min, max);
}
