/*
 * Zorbage: an algebraic data hierarchy for use in numeric processing.
 *
 * Copyright (C) 2016-2020 Barry DeZonia
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package nom.bdezonia.zorbage.algorithm;

import nom.bdezonia.zorbage.algebra.Algebra;
import nom.bdezonia.zorbage.algebra.G;
import nom.bdezonia.zorbage.datasource.IndexedDataSource;
import nom.bdezonia.zorbage.storage.Storage;
import nom.bdezonia.zorbage.type.int64.SignedInt64Member;

/**
 * 
 * @author Barry DeZonia
 *
 */
public class SampleWithoutReplacement {

	private SampleWithoutReplacement() { }
	
	/**
	 * 
	 * @param algebra
	 * @param n
	 * @param a
	 * @param b
	 */
	public static <T extends Algebra<T,U>, U>
		void compute(T algebra, long n, IndexedDataSource<U> a, IndexedDataSource<U> b)
	{
		long aSize = a.size();
		long bSize = b.size();
		if (n > aSize)
			throw new IllegalArgumentException("cannot take "+n+" samples from "+aSize+" elements without replacement");
		if (n > bSize)
			throw new IllegalArgumentException("cannot fit "+n+" samples in "+bSize+" spaces");
		SignedInt64Member idx = G.INT64.construct();
		IndexedDataSource<SignedInt64Member> indices = Storage.allocate(aSize, idx);
		for (long i = 0; i < aSize; i++) {
			idx.setV(i);
			indices.set(i, idx);
		}
		Shuffle.compute(G.INT64, indices);
		U tmp = algebra.construct();
		for (long i = 0; i < n; i++) {
			indices.get(i, idx);
			a.get(idx.v(), tmp);
			b.set(i, tmp);
		}
	}
}

@@ -1465,16 +1465,93 @@
 rithm;%0A%0A
+import java.math.BigInteger;%0Aimport java.util.concurrent.ThreadLocalRandom;%0A%0A
 import n
@@ -2442,16 +2442,63 @@
 ruct();%0A
+%09%09SignedInt64Member tmp = G.INT64.construct();%0A
 %09%09Indexe
@@ -2555,21 +2555,17 @@
 llocate(
-aSize
+n
 , idx);%0A
@@ -2562,29 +2562,24 @@
 (n, idx);%0A%09%09
-for (
 long i = 0; 
@@ -2581,54 +2581,237 @@
 = 0;
- i %3C aSize; i++) %7B%0A%09%09%09idx.setV(i);
+%0A%09%09while (i %3C n) %7B%0A%09%09%09BigInteger num = new BigInteger(63, ThreadLocalRandom.current());%0A%09%09%09num = num.mod(BigInteger.valueOf(n));%0A%09%09%09idx.setV(num.longValue());%0A%09%09%09boolean done = true;%0A%09%09%09for (long j = 0; j %3C i; j++) %7B
 %0A%09%09%09
+%09
 indices.
 set(
@@ -2810,69 +2810,156 @@
 ces.
-set(i, idx);%0A%09%09%7D%0A%09%09Shuffle.compute(G.INT64, indices);%0A%09%09U tmp
+get(j, tmp);%0A%09%09%09%09if (tmp.v() == idx.v()) %7B%0A%09%09%09%09%09done = false;%0A%09%09%09%09%09break;%0A%09%09%09%09%7D%0A%09%09%09%7D%0A%09%09%09if (done) %7B%0A%09%09%09%09indices.set(i, idx);%0A%09%09%09%09i++;%0A%09%09%09%7D%0A%09%09%7D%0A%09%09U x
  = a
@@ -2985,21 +2985,16 @@
 %0A%09%09for (
-long 
 i = 0; i
@@ -3048,19 +3048,17 @@
 dx.v(), 
-tmp
+x
 );%0A%09%09%09b.
@@ -3064,19 +3064,17 @@
 .set(i, 
-tmp
+x
 );%0A%09%09%7D%0A%09

Make SampleWithoutReplacement use much less temporary space