SingleStructureRandomGenerator.java

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 *  Copyright (C) 1997-2007  The Chemistry Development Kit (CDK) project
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package org.openscience.cdk.structgen;

import java.util.Random;

import org.openscience.cdk.exception.CDKException;
import org.openscience.cdk.graph.ConnectivityChecker;
import org.openscience.cdk.interfaces.IAtom;
import org.openscience.cdk.interfaces.IAtomContainer;
import org.openscience.cdk.interfaces.IMolecule;
import org.openscience.cdk.tools.ILoggingTool;
import org.openscience.cdk.tools.LoggingToolFactory;
import org.openscience.cdk.tools.SaturationChecker;
import org.openscience.cdk.tools.manipulator.BondManipulator;

/**
 * Randomly generates a single, connected, correctly bonded structure for 
 * a given molecular formula.
 * To see it working run the graphical 
 * test org.openscience.cdk.test.SingleStructureRandomGeneratorTest
 * and add more structures to the panel using the "More" button. 
 * In order to use this class, use MFAnalyser to get an AtomContainer from 
 * a molecular formula string.
 *
 * <p>Assign hydrogen counts to each heavy atom. The hydrogens should not be
 * in the atom pool but should be assigned implicitly to the heavy atoms in 
 * order to reduce computational cost.
 * Assign this AtomContainer to the  
 * SingleStructureRandomGenerator and retrieve a randomly generated, but correctly bonded
 * structure by using the generate() method. You can then repeatedly call
 * the generate() method in order to retrieve further structures. 
 * 
 * <p>Agenda:
 * <ul>
 *  <li>add a method for randomly adding hydrogens to the atoms
 *  <li>add a seed for random generator for reproducability
 * </ul>
 *
 * @author      steinbeck
 * @cdk.created 2001-09-04
 * @cdk.module  structgen
 * @cdk.githash
 */
public class SingleStructureRandomGenerator {
	
	ILoggingTool logger =
        LoggingToolFactory.createLoggingTool(SingleStructureRandomGenerator.class);
	
	IAtomContainer atomContainer;
	SaturationChecker satCheck;
	Random random = null;

	/**
	 * Constructor for the SingleStructureRandomGenerator object.
	 */
	public SingleStructureRandomGenerator(long seed) throws java.lang.Exception
	{
		satCheck = new SaturationChecker();
		random = new Random(seed);
	}

	/**
	 * Constructor for the SingleStructureRandomGenerator object.
	 */
	public SingleStructureRandomGenerator() throws java.lang.Exception
	{
		this((long)11000);
	}

	
	/**
	 * Sets the AtomContainer attribute of the SingleStructureRandomGenerator object.
	 *
	 * @param  ac  The new AtomContainer value
	 */
	public void setAtomContainer(IAtomContainer ac)
	{
		this.atomContainer = ac;
	}

	/**
	 * Generates a random structure based on the atoms in the given IAtomContainer.
	 */
	public IMolecule generate() throws CDKException
	{
		boolean structureFound = false;
		boolean bondFormed;
		double order;
		double max, cmax1, cmax2;
		int iteration = 0;
		IAtom partner;
		IAtom atom;
		do
		{
			iteration++;
			atomContainer.removeAllElectronContainers();
			do
			{
				bondFormed = false;
				for (int f = 0; f < atomContainer.getAtomCount(); f++)
				{
					atom = atomContainer.getAtom(f);

					if (!satCheck.isSaturated(atom, atomContainer))
					{
						partner = getAnotherUnsaturatedNode(atom);
						if (partner != null)
						{
							cmax1 = satCheck.getCurrentMaxBondOrder(atom, atomContainer);
				
							cmax2 = satCheck.getCurrentMaxBondOrder(partner, atomContainer);
							max = Math.min(cmax1, cmax2);
							order = Math.min(Math.max(1.0, random.nextInt((int)Math.round(max))), 3.0);
							logger.debug("Forming bond of order ", order);
							atomContainer.addBond(
								atomContainer.getBuilder().newBond(
									atom, partner, BondManipulator.createBondOrder(order)
								)
							);
							bondFormed = true;
						}
					}
				}
			} while (bondFormed);
			if (ConnectivityChecker.isConnected(atomContainer)
					&& satCheck.allSaturated(atomContainer))
			{
				structureFound = true;
			}
		} while (!structureFound && iteration < 20);
		logger.debug("Structure found after #iterations: ", iteration);	
		return atomContainer.getBuilder().newMolecule(atomContainer);
	}

	
	/**
	 * Gets the AnotherUnsaturatedNode attribute of the SingleStructureRandomGenerator object.
	 *
	 * @return                The AnotherUnsaturatedNode value
	 */
	private IAtom getAnotherUnsaturatedNode(IAtom exclusionAtom) throws CDKException
	{
		IAtom atom;
		int next = random.nextInt(atomContainer.getAtomCount());

		for (int f = next; f < atomContainer.getAtomCount(); f++)
		{
			atom = atomContainer.getAtom(f);
			if (!satCheck.isSaturated(atom, atomContainer)
					&& exclusionAtom != atom 
					&& !atomContainer.getConnectedAtomsList(exclusionAtom).contains(atom))
			{
				return atom;
			}
		}
		for (int f = 0; f < next; f++)
		{
			atom = atomContainer.getAtom(f);
			if (!satCheck.isSaturated(atom, atomContainer) 
					&& exclusionAtom != atom 
					&& !atomContainer.getConnectedAtomsList(exclusionAtom).contains(atom))
			{
				return atom;
			}
		}
		return null;
	}

}