Bug 88653 [Commands] performance: 50% of perspective switch in ParameterizedCommand.equals()
Build: I20050315 Setup: 1) Workspace with three projects, org.eclipse.jdt.core, org.eclipse.swt, and org.eclipse.swt.win32 2) Editor open on org.eclipse.jdt.internal.compiler.parser.Parser.java 3) Default Java perspective and Resource perspective open My test was to switch between the two open perspectives about five times using Ctrl+F8. The profiler showed 50% of the time in ParameterizedCommand.equals() and in the methods called by that equals implementation (Util.equals() and Command.equals()). The main problem is probably in the number of times this method is called (about 1.6 million times). This seems to be caused by a large number of property change events: ExternalActionManager$CommandCallback.bindingManagerChanged is called 30 times. This in turn calls ActionContributionItem$1.propertyChange, which is called 4787 times. The number of method calls explodes as you go down the call stack, until the equals method that is called 1.6 million times. I will attach profiler output to show more details. If the number of change events can't be reduced, it looks like the implementation of ParameterizedCommand.equals() can be made faster by first comparing the cached hash code. Only if the hash codes are the same does it need to do the remainder of the equality testing.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/ParameterizedCommand.java
.get(i);
				final List newCombination = new ArrayList(combinationSize + 1);
				newCombination.add(parameterization);
				newCombination.addAll(combination);
				returnValue.add(newCombination);
			}
		}
		return returnValue;
	}
	/**
	 * <p>
	 * Generates all the possible combinations of command parameterizations for
	 * the given command. If the command has no parameters, then this is simply
	 * a parameterized version of that command. If a parameter is optional, both
	 * the included and not included cases are considered.
	 * </p>
	 * <p>
	 * If one of the parameters cannot be loaded due to a
	 * <code>ParameterValuesException</code>, then it is simply ignored.
	 * </p>
	 * 
	 * @param command
	 *            The command for which the parameter combinations should be
	 *            generated; must not be <code>null</code>.
	 * @return A collection of <code>ParameterizedCommand</code> instances
	 *         representing all of the possible combinations. This value is
	 *         never empty and it is never <code>null</code>.
	 * @throws NotDefinedException
	 *             If the command is not defined.
	 */