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Improve performance and reduce allocations in DecisionTreeBuilder<T>.

This commit is contained in:
Gert Driesen 2018-10-20 12:12:08 +02:00 committed by Ryan Nowak
parent 29b50c7b64
commit 3c9086e3d0
1 changed files with 12 additions and 9 deletions
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21
shared/Microsoft.AspNetCore.Routing.DecisionTree.Sources/DecisionTreeBuilder.cs
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@ -74,14 +74,16 @@ namespace Microsoft.AspNetCore.Routing.DecisionTree
{
public static DecisionTreeNode<TItem> GenerateTree(IReadOnlyList<TItem> items, IClassifier<TItem> classifier)
{
var itemDescriptors = new List<ItemDescriptor<TItem>>();
for (var i = 0; i < items.Count; i++)
var itemCount = items.Count;
var itemDescriptors = new List<ItemDescriptor<TItem>>(itemCount);
for (var i = 0; i < itemCount; i++)
{
var item = items[i];
itemDescriptors.Add(new ItemDescriptor<TItem>()
{
Criteria = classifier.GetCriteria(items[i]),
Criteria = classifier.GetCriteria(item),
Index = i,
Item = items[i],
Item = item,
});
}
@ -95,7 +97,7 @@ namespace Microsoft.AspNetCore.Routing.DecisionTree
private static DecisionTreeNode<TItem> GenerateNode(
TreeBuilderContext context,
DecisionCriterionValueEqualityComparer comparer,
IList<ItemDescriptor<TItem>> items)
List<ItemDescriptor<TItem>> items)
{
// The extreme use of generics here is intended to reduce the number of intermediate
// allocations of wrapper classes. Performance testing found that building these trees allocates
@ -156,16 +158,17 @@ namespace Microsoft.AspNetCore.Routing.DecisionTree
foreach (var branch in criterion.Value)
{
var reducedItems = new List<ItemDescriptor<TItem>>();
bool hasReducedItems = false;
foreach (var item in branch.Value)
{
if (context.MatchedItems.Add(item))
{
reducedItems.Add(item);
hasReducedItems = true;
}
}
if (reducedItems.Count > 0)
if (hasReducedItems)
{
var childContext = new TreeBuilderContext(context);
childContext.CurrentCriteria.Add(criterion.Key);
@ -189,7 +192,7 @@ namespace Microsoft.AspNetCore.Routing.DecisionTree
return new DecisionTreeNode<TItem>()
{
Criteria = reducedCriteria.ToList(),
Criteria = reducedCriteria,
Matches = matches,
};
}