SE: Caching: Cache "GetHashCode" for SymbolicValue #6968

martin-strecker-sonarsource · 2023-03-21T10:38:59Z

Part of #6964

martin-strecker-sonarsource · 2023-03-21T10:40:50Z

analyzers/src/SonarAnalyzer.Common/SymbolicExecution/Roslyn/SymbolicValue.cs

@@ -37,6 +39,11 @@ public sealed record SymbolicValue
        public IEnumerable<SymbolicConstraint> AllConstraints =>
            Constraints.Values;

+        public SymbolicValue()
+        {
+            hashCode = new(() => HashCode.DictionaryContentHash(Constraints), LazyThreadSafetyMode.ExecutionAndPublication);


For LazyThreadSafetyMode see https://learn.microsoft.com/en-us/dotnet/api/system.threading.lazythreadsafetymode?view=net-8.0

martin-strecker-sonarsource · 2023-03-21T17:00:29Z

Impact on allocations:

Corniel · 2023-03-22T21:49:15Z

So it reduced the number of iterations on your dictionary with a factor two? That's nice. Did you create a benchmark too?

martin-strecker-sonarsource · 2023-03-23T08:06:05Z

Did you create a benchmark too?

No. This is done with the AnalyzerRunner and the Visual Studio diagnostics tool. I may add a markdown file to our docs on how to do that. It might come in handy as we have quite some of these optimizations to do and this helps with guiding in the right direction.

martin-strecker-sonarsource · 2023-03-23T12:57:11Z

analyzers/src/SonarAnalyzer.Common/SymbolicExecution/Roslyn/SymbolicValue.cs

+        private readonly ImmutableDictionary<Type, SymbolicConstraint> constraints = ImmutableDictionary<Type, SymbolicConstraint>.Empty;
+        private int? constraintsHashCode;
+
        // SymbolicValue can have only one constraint instance of specific type at a time
-        private ImmutableDictionary<Type, SymbolicConstraint> Constraints { get; init; } = ImmutableDictionary<Type, SymbolicConstraint>.Empty;
+        private ImmutableDictionary<Type, SymbolicConstraint> Constraints
+        {
+            get => constraints;
+            init
+            {
+                if (constraints != value)
+                {
+                    constraints = value;
+                    constraintsHashCode = null;
+                }
+            }
+        }


There is also

sonar-dotnet/analyzers/src/SonarAnalyzer.Common/SymbolicExecution/Roslyn/ProgramState.cs

Lines 138 to 143 in f3c2ea1

HashCode.Combine(

HashCode.DictionaryContentHash(OperationValue),

HashCode.DictionaryContentHash(SymbolValue),

HashCode.DictionaryContentHash(CaptureOperation),

HashCode.EnumerableContentHash(PreservedSymbols),

HashCode.EnumerableContentHash(Exceptions));

and I want to use the same pattern there as well. There it is more important to reset the cached hashcode in the init setter. There we can do this, to make the declaration more compact:

private readonly ImmutableDictionary<IOperation, SymbolicValue> operationValue; private int? operationValueHashCode; private ImmutableDictionary<IOperation, SymbolicValue> OperationValue { get => operationValue; init => SetHashCodeCachedField(value, ref operationValue, ref operationValueHashCode); } private static void SetHashCodeCachedField<T>(T value, ref T backingField, ref int? backingFieldHashCode) where T: class { if (value != backingField) { backingField = value; backingFieldHashCode = null; } }

The init and ref trick sounds good in principle.

backingFieldHashCode should not be a parameter, the method can just reset it directly.

The SetHashCodeCachedField method doesn't make sense in this class. It will come in handy in ProgramState. I just wanted to make sure we do the caching in both classes the same way, so we don't solve the same problem differently in these highly related classes. Slight differences like this should be fine though.

That's also my understanding that it should not be here, because it's not needed (yet).

pavel-mikula-sonarsource

LGTM with a small rename before merging

pavel-mikula-sonarsource · 2023-03-23T14:09:40Z

analyzers/src/SonarAnalyzer.Common/SymbolicExecution/Roslyn/SymbolicValue.cs

@@ -35,8 +35,22 @@ public sealed record SymbolicValue
        public static readonly SymbolicValue True = NotNull.WithConstraint(BoolConstraint.True);
        public static readonly SymbolicValue False = NotNull.WithConstraint(BoolConstraint.False);

+        private readonly ImmutableDictionary<Type, SymbolicConstraint> constraints = ImmutableDictionary<Type, SymbolicConstraint>.Empty;
+        private int? constraintsHashCode;


It is and will be hash code for the entire class. No matter how much mess we add.

Suggested change

private int? constraintsHashCode;

private int? hashCode;

pavel-mikula-sonarsource · 2023-03-23T14:11:34Z

analyzers/src/SonarAnalyzer.Common/SymbolicExecution/Roslyn/SymbolicValue.cs

+        private readonly ImmutableDictionary<Type, SymbolicConstraint> constraints = ImmutableDictionary<Type, SymbolicConstraint>.Empty;
+        private int? constraintsHashCode;
+
        // SymbolicValue can have only one constraint instance of specific type at a time
-        private ImmutableDictionary<Type, SymbolicConstraint> Constraints { get; init; } = ImmutableDictionary<Type, SymbolicConstraint>.Empty;
+        private ImmutableDictionary<Type, SymbolicConstraint> Constraints
+        {
+            get => constraints;
+            init
+            {
+                if (constraints != value)
+                {
+                    constraints = value;
+                    constraintsHashCode = null;
+                }
+            }
+        }


The init and ref trick sounds good in principle.

backingFieldHashCode should not be a parameter, the method can just reset it directly.

pavel-mikula-sonarsource · 2023-03-23T14:12:09Z

analyzers/tests/SonarAnalyzer.UnitTest/SymbolicExecution/Roslyn/SymbolicValueTest.cs

+                .NotBe(SymbolicValue.Null.GetHashCode()).And
+                .NotBe(SymbolicValue.NotNull.GetHashCode()).And
+                .NotBe(SymbolicValue.True.GetHashCode()).And


Let's put the .And at the beginning of the line. LIke &&

pavel-mikula-sonarsource

Still LGTM

pavel-mikula-sonarsource · 2023-03-24T15:07:51Z

analyzers/src/SonarAnalyzer.Common/SymbolicExecution/Roslyn/SymbolicValue.cs

+            get => constraints;
+            init
+            {
+                if (constraints != value)


This condition is not covered when values are the same. We don't use it that way. And we actually shouldn't, as we should attempt no-operation when possible.

Do we really need the condition then?

It doesn't hurt to keep it, IMO. It allows doing something like, e.g. with Constraints = someCond ? Empty : Constraints. I could add a test case to increase test coverage if that is a concern.

I would remove the condition. It's one more additional Equals check on a hot path that doesn't need to be there.

And so far, we didn't need it. And it's against the intended usage of the property. We can always add it back if we need to.

That's fine with me.

analyzers/src/SonarAnalyzer.Common/SymbolicExecution/Roslyn/SymbolicValue.cs

sonarcloud · 2023-03-27T10:15:46Z

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

sonarcloud · 2023-03-27T10:20:14Z

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

100.0% Coverage
0.0% Duplication

martin-strecker-sonarsource added the Sprint: SE label Mar 21, 2023

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martin-strecker-sonarsource force-pushed the Martin/SE_6964_01_Cache_GetHashcode branch from 2a0e127 to f4f2e29 Compare March 21, 2023 14:35

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SE: Add caching for reusable data structures #6964

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martin-strecker-sonarsource added 3 commits March 23, 2023 11:19

Add cache for SymbolicValue

65d1021

Add copy constructor to reset "Lazy"

49b5c30

Remove duplicate code

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martin-strecker-sonarsource force-pushed the Martin/SE_6964_01_Cache_GetHashcode branch from 703c93e to 59cf2fb Compare March 23, 2023 10:20

martin-strecker-sonarsource added 4 commits March 23, 2023 11:31

Use nullable int instead on lazy

80c001e

Fix implementation

cbd6fae

GetHashCode tests for SymbolicValue

83d3aae

Add more cases.

389b423

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Supress warning

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Formatting

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Rename field

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SE: Maintenance: Cache GetHashCode for ProgramState #6983

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martin-strecker-sonarsource commented Mar 27, 2023

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analyzers/src/SonarAnalyzer.Common/SymbolicExecution/Roslyn/SymbolicValue.cs Outdated Show resolved Hide resolved

Remove if

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pavel-mikula-sonarsource merged commit 36047e9 into feature/SE Mar 27, 2023

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pavel-mikula-sonarsource pushed a commit that referenced this pull request Mar 28, 2023

SE: Caching: Cache "GetHashCode" for SymbolicValue (#6968)

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SE: Caching: Cache "GetHashCode" for SymbolicValue (#6968)

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SE: Caching: Cache "GetHashCode" for SymbolicValue (#6968)

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SE: Caching: Cache "GetHashCode" for SymbolicValue #6968

SE: Caching: Cache "GetHashCode" for SymbolicValue #6968

martin-strecker-sonarsource commented Mar 21, 2023

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sonarcloud bot commented Mar 27, 2023

sonarcloud bot commented Mar 27, 2023

	HashCode.Combine(
	HashCode.DictionaryContentHash(OperationValue),
	HashCode.DictionaryContentHash(SymbolValue),
	HashCode.DictionaryContentHash(CaptureOperation),
	HashCode.EnumerableContentHash(PreservedSymbols),
	HashCode.EnumerableContentHash(Exceptions));

SE: Caching: Cache "GetHashCode" for SymbolicValue #6968

SE: Caching: Cache "GetHashCode" for SymbolicValue #6968

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