opencog-atomspace / tests / atomspace / HashMixUTest.cxxtest

/*
 * tests/atomspace/HashMixUTest.cxxtest
 *
 * Copyright (C) 2019 Linas Vepstas <linasvepstas@gmail.com>
 * All Rights Reserved
 *
 * Written by Linas Vepstas <linasvepstas@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License v3 as
 * published by the Free Software Foundation and including the exceptions
 * at http://opencog.org/wiki/Licenses
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, write to:
 * Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <opencog/atomspace/AtomSpace.h>
#include <opencog/atoms/base/Node.h>
#include <opencog/util/Logger.h>
#include <opencog/util/platform.h>

using namespace opencog;

class HashMixUTest :  public CxxTest::TestSuite
{
private:
	AtomSpacePtr as;

public:
	HashMixUTest()
	{
	}

	void setUp()
	{
		as = createAtomSpace();
	}

	void tearDown()
	{
	}

	void HashMixer(int num_atoms, int width)
	{
		Handle h = as->add_node(CONCEPT_NODE, "foobar");

		// This test is successful if it runs to completion. A hash
		// function with a collision will cause this to hang for a
		// very very very long time! (Because the collision will
		// force a Link compare-by-content, which will take about
		// (width) power-of (num_atoms) so 14 Billion years if there
		// is an actual hash collision.
		for (int i = 0; i < num_atoms; i++)
		{
			// Create a width-ary tree. (e.g. binary tree for width=2)
			HandleSeq hs;
			for (int j=0; j< width; j++) hs.push_back(h);
			h = as->add_link(LIST_LINK, std::move(hs));
		}

		// Just for grins. This is meaningless.
		size_t sz = as->get_size();

		printf("Final size is %zu\n", sz);
		TS_ASSERT_EQUALS(sz, num_atoms+1);

		while (h->is_link())
		{
			Handle h2 = h->getOutgoingAtom(0);
			bool done = as->extract_atom(h);
			TS_ASSERT_EQUALS(done, true);
			h = h2;
			sz --;
		}
		TS_ASSERT_EQUALS(sz, 1);
		as->clear();
	}

	void testHashMixing()
	{
		logger().info("BEGIN TEST: %s", __FUNCTION__);
		HashMixer(134001, 2);
		HashMixer(136301, 3);
		HashMixer( 74501, 4);
		HashMixer( 74601, 5);
		HashMixer( 74701, 6);
		HashMixer( 74801, 7);

		logger().info("END TEST: %s", __FUNCTION__);
	}
};