Re: Memory allocation overhead

>>>>> "Colin" == Colin Paul Adams <[email protected]> writes:

    Colin> I am currently trying this with the iterators used to
    Colin> evaluate XPath sequences. I am retaining copies on a once
    Colin> DS_ARRAYED_STACK. So far, this is actually increasing the
    Colin> runtime (but it appears sensitive to the size of the stack,
    Colin> so I am currently trying with just a DS_CELL to see if this
    Colin> is better).

In fact the DS_CELL proved to be slower than a small stack.

But I am now wondering about code inlining. It appears that gec does
not inline all three routines new_child_tree_iterator, release_iterator
and new_descendant_tree_iterator in the code below. (Note that the bulk of
the class is commented out. The test program then runs in 21 minutes
and 8 seconds, as opposed to 20 minutes and 28 seconds (+- 3 seconds)
with the creations inlined, and no call to release_iterator (there is
an extra assignment to Void of the iterator passed to release_iterator
following the call to release_iterator, but I hardly think that can
account for the difference). With all the commented-out code restored,
(and assignemt of 4 default values to attributes in the creation
procedures, which costs about 6 seconds) the time rises to 21 minutes
and 52 seconds. 

I can't account for any of this.


class XM_XPATH_ITERATOR_POOL

feature -- Creation

	new_child_tree_iterator (a_starting_node: XM_XPATH_TREE_NODE; a_node_test: XM_XPATH_NODE_TEST): XM_XPATH_TREE_CHILD_ENUMERATION is
			-- New or reused child iterator for `a_starting_node'
		require
			starting_node_not_void: a_starting_node /= Void
			node_test_not_void: a_node_test /= Void
		do
--			if child_tree_iterators.is_empty then
				create Result.make (a_starting_node, a_node_test)
--			else
--				Result := child_tree_iterators.item
--				Result.make (a_starting_node, a_node_test)
--				child_tree_iterators.remove
--			end
		ensure
			new_child_tree_iterator_not_void: Result /= Void
		end

	new_descendant_tree_iterator (a_starting_node: XM_XPATH_TREE_NODE; a_node_test: XM_XPATH_NODE_TEST;
		a_include_self: BOOLEAN): XM_XPATH_TREE_DESCENDANT_ENUMERATION is
			-- New or reused descendant iterator for `a_starting_node'
		require
			starting_node_not_void: a_starting_node /= Void
			node_test_not_void: a_node_test /= Void
		do
--			if descendant_tree_iterators.is_empty then
				create Result.make (a_starting_node, a_node_test, a_include_self)
--			else
--				Result := descendant_tree_iterators.item
--				Result.make (a_starting_node, a_node_test, a_include_self)
--				descendant_tree_iterators.remove
--			end
		ensure
			new_descendant_tree_iterator_not_void: Result /= Void
		end
			
feature -- Removal

	release_iterator (a_iterator: XM_XPATH_SEQUENCE_ITERATOR [XM_XPATH_ITEM]) is
			-- Return `a_iterator' to free memory.
		require
			a_iterator_not_void: a_iterator /= Void
		do
--			if a_iterator.is_tree_child_enumeration then
--				if child_tree_iterators.count < Maximum_queue_length then
--					child_tree_iterators.put (a_iterator.as_tree_child_enumeration)
--				end
--			elseif a_iterator.is_tree_descendant_enumeration then
--				if descendant_tree_iterators.count < Maximum_queue_length then
--					descendant_tree_iterators.put (a_iterator.as_tree_descendant_enumeration)
--				end
--			end
		end

feature {NONE} -- Implementation

	Maximum_queue_length: INTEGER is 5
			-- Limit on queue size for any single iterator type

--	child_tree_iterators: DS_ARRAYED_STACK [XM_XPATH_TREE_CHILD_ENUMERATION]
--			-- Spare iterators over the child axis of XM_XPATH_TREE_NODEs
--		once
--			create Result.make (Maximum_queue_length)
--		ensure
--			child_tree_iterators_not_void: Result /= Void
--		end

--	descendant_tree_iterators: DS_ARRAYED_STACK [XM_XPATH_TREE_DESCENDANT_ENUMERATION]
--			-- Spare iterators over the descendant axis of XM_XPATH_TREE_NODEs
--		once
--			create Result.make (Maximum_queue_length)
--		ensure
--			descendant_tree_iterators_not_void: Result /= Void
--		end

end

-- 
Colin Adams
Preston Lancashire

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