Move the IsLeft/IsRight decision out of the loop and use computed substring set by IDisposable · Pull Request #88516 · dotnet/runtime

IDisposable · 2023-07-07T10:50:27Z

While reviewing #87510, I noticed the inline code in the comparers seems like since it's in the hot-loop path, might be faster to move the IsLeft conditionalized code out of the loop by adding a static Slicer to the comparator. The Slicer is the same logic as was originally in the bodies of the Equals and GetHashCode methods, and also matches the delegates that were being passed to the internal CreateAnalysisResults method.

The slicing is really only changed once per Count, so move the IsLeft-dependent logic into aggressively inlined Slicer extension method because that makes things a bit faster and slightly reduces allocations.

~~Builds on #88709 as that's a trivially true change.~~ Has been merged now.

The summary of changes:

Eliminate the the inner TryUseSubstring because we can just early return the calculated results as we build them
Hoist the calculation of acceptableNonUniqueCount out to the top level since it never changes (which means we pass that into the HasSufficientUniquenessFactor method for it to "use up" internally (passed by value, so unchanged at call-site)
Eliminated the delegate ReadOnlySpan<char> GetSpan and use, which helps reduce dynamic dispatch overhead in the CreateAnalysisResults method
Eliminated the IsLeft field of the SubstringComparer since we can tell by the Index being negative that we're doing right-justified slicing (and documented that on the class)
Changed the logic managing the Index and Count on the comparer for right-justified substrings.
Added [MethodImpl(MethodImplOptions.AggressiveInlining)] to the Equals and GetHashCode overrides.

ghost · 2023-07-07T10:50:41Z

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Issue Details

While reviewing #87510, I noticed the inline code in the Comparers seems like since it's in the hot-loop path, might be faster to move the IsLeft conditionalized code out of the loop by adding a Slicer to the comparator. The Slicer is the same logic as was in the bodies of the Equals and GetHashCode methods, and indeed also matches the delegate that was passed to the internal CreateAnalysisResults method.

The slicing is really only changed once per Count, so move the IsLeft-dependent logic into aggressively inlined SliceLeft and SliceRight to see if that makes things faster. Also reuses the same slicers for the calls to the CreateAnalysisResults so the will get the same JIT perf benefits.

Also made a subtle tweak because we know that ignoreCase is true (due to the test above), so can set the starting state of canSwitchIgnoreCaseToCaseSensitive explicitly to true.

BenchmarkDotNet=v0.13.2.2052-nightly, OS=Windows 11 (10.0.22631.1972)
Intel Core i7-10875H CPU 2.30GHz, 1 CPU, 16 logical and 8 physical cores
.NET SDK=8.0.100-preview.7.23322.33
[Host] : .NET 8.0.0 (8.0.23.32106), X64 RyuJIT AVX2
Job-ZWELZX : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT AVX2
Job-KUEFVA : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT AVX2
PowerPlanMode=00000000-0000-0000-0000-000000000000 Arguments=/p:EnableUnsafeBinaryFormatterSerialization=true IterationTime=250.0000 ms MaxIterationCount=20 MinIterationCount=15 WarmupCount=1

Method	Job	Toolchain	Count	Mean	Error	StdDev	Median	Min	Max	Ratio	MannWhitney(3ms)	RatioSD	Gen0	Gen1	Gen2	Allocated	Alloc Ratio
ToFrozenDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	2,057.56 ns	23.550 ns	20.877 ns	2,053.70 ns	2,004.57 ns	2,095.98 ns	1.26	Same	0.03	0.2027	-	-	1720 B	1.00
ToFrozenDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	1,644.78 ns	32.011 ns	35.580 ns	1,631.83 ns	1,603.70 ns	1,715.13 ns	1.00	Base	0.00	0.2047	-	-	1720 B	1.00

TryGetValue_True_FrozenDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	63.10 ns	0.752 ns	0.628 ns	63.24 ns	61.43 ns	63.91 ns	1.00	Same	0.02	-	-	-	-	NA
TryGetValue_True_FrozenDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	63.30 ns	0.842 ns	0.788 ns	63.31 ns	62.34 ns	65.07 ns	1.00	Base	0.00	-	-	-	-	NA

ToFrozenDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	11,800.30 ns	139.610 ns	123.760 ns	11,764.33 ns	11,681.12 ns	12,075.98 ns	1.26	Same	0.01	1.4098	0.0470	-	12112 B	1.00
ToFrozenDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	9,348.64 ns	91.765 ns	76.628 ns	9,367.20 ns	9,209.04 ns	9,481.99 ns	1.00	Base	0.00	1.4145	0.0372	-	12112 B	1.00

TryGetValue_True_FrozenDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	647.76 ns	12.870 ns	12.640 ns	645.45 ns	630.03 ns	677.18 ns	1.00	Same	0.02	-	-	-	-	NA
TryGetValue_True_FrozenDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	645.03 ns	8.896 ns	8.321 ns	645.45 ns	631.23 ns	658.04 ns	1.00	Base	0.00	-	-	-	-	NA

ToFrozenDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	107,105.57 ns	1,078.411 ns	955.984 ns	106,742.36 ns	106,269.73 ns	109,294.56 ns	1.26	Same	0.01	11.1301	2.5685	-	94864 B	1.00
ToFrozenDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	84,805.63 ns	1,384.405 ns	1,294.973 ns	84,801.32 ns	82,494.28 ns	87,164.12 ns	1.00	Base	0.00	11.2434	2.6455	-	94864 B	1.00

TryGetValue_True_FrozenDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	7,823.96 ns	106.727 ns	99.833 ns	7,841.29 ns	7,668.40 ns	7,999.15 ns	1.04	Same	0.02	-	-	-	-	NA
TryGetValue_True_FrozenDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	7,542.00 ns	104.779 ns	92.883 ns	7,555.03 ns	7,364.24 ns	7,702.98 ns	1.00	Base	0.00	-	-	-	-	NA

ToFrozenDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	1,641,164.67 ns	23,876.639 ns	22,334.223 ns	1,633,353.12 ns	1,612,245.00 ns	1,676,639.38 ns	1.18	Same	0.02	143.7500	143.7500	143.7500	926133 B	1.00
ToFrozenDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	1,393,440.90 ns	17,878.950 ns	16,723.981 ns	1,394,471.88 ns	1,360,370.31 ns	1,421,018.75 ns	1.00	Base	0.00	145.8333	145.8333	145.8333	926134 B	1.00

TryGetValue_True_FrozenDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	129,167.96 ns	2,134.712 ns	1,996.811 ns	129,264.68 ns	124,220.63 ns	132,173.42 ns	1.01	Same	0.02	-	-	-	-	NA
TryGetValue_True_FrozenDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	128,107.54 ns	1,706.036 ns	1,595.827 ns	127,981.50 ns	126,341.48 ns	131,397.43 ns	1.00	Base	0.00	-	-	-	-	NA

ToDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	138.87 ns	1.287 ns	1.204 ns	138.58 ns	136.88 ns	141.00 ns	0.94	Same	0.02	0.0526	-	-	440 B	1.00
ToDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	147.84 ns	2.518 ns	2.355 ns	147.02 ns	145.32 ns	153.22 ns	1.00	Base	0.00	0.0526	-	-	440 B	1.00

ToImmutableDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	1,299.27 ns	83.702 ns	96.391 ns	1,250.37 ns	1,202.89 ns	1,479.53 ns	1.12	Same	0.08	0.0860	-	-	736 B	1.00
ToImmutableDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	1,178.81 ns	16.472 ns	15.407 ns	1,171.80 ns	1,158.97 ns	1,204.85 ns	1.00	Base	0.00	0.0847	-	-	736 B	1.00

TryGetValue_True_Dictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	128.08 ns	1.673 ns	1.483 ns	128.16 ns	125.29 ns	130.57 ns	1.00	Same	0.01	-	-	-	-	NA
TryGetValue_True_Dictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	128.21 ns	1.885 ns	1.763 ns	128.02 ns	125.36 ns	131.44 ns	1.00	Base	0.00	-	-	-	-	NA

TryGetValue_True_ImmutableDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	164.46 ns	2.012 ns	1.882 ns	164.70 ns	162.56 ns	168.03 ns	1.00	Same	0.01	-	-	-	-	NA
TryGetValue_True_ImmutableDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10	164.62 ns	2.097 ns	1.962 ns	163.06 ns	162.89 ns	167.53 ns	1.00	Base	0.00	-	-	-	-	NA

ToDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	1,097.04 ns	21.699 ns	20.298 ns	1,095.36 ns	1,072.24 ns	1,134.88 ns	1.13	Same	0.03	0.3714	0.0043	-	3128 B	1.00
ToDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	972.18 ns	16.163 ns	15.119 ns	968.03 ns	958.70 ns	1,002.61 ns	1.00	Base	0.00	0.3706	0.0039	-	3128 B	1.00

ToImmutableDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	17,821.67 ns	327.754 ns	306.582 ns	17,853.37 ns	17,381.97 ns	18,333.97 ns	0.95	Same	0.02	0.7301	-	-	6496 B	1.00
ToImmutableDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	18,780.61 ns	259.705 ns	230.222 ns	18,796.94 ns	18,384.63 ns	19,208.59 ns	1.00	Base	0.00	0.7449	-	-	6496 B	1.00

TryGetValue_True_Dictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	1,442.70 ns	19.214 ns	17.973 ns	1,442.10 ns	1,410.93 ns	1,475.64 ns	0.95	Same	0.01	-	-	-	-	NA
TryGetValue_True_Dictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	1,524.14 ns	21.632 ns	18.064 ns	1,521.86 ns	1,490.48 ns	1,565.28 ns	1.00	Base	0.00	-	-	-	-	NA

TryGetValue_True_ImmutableDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	1,772.76 ns	24.517 ns	22.934 ns	1,769.24 ns	1,735.35 ns	1,807.67 ns	0.88	Same	0.02	-	-	-	-	NA
TryGetValue_True_ImmutableDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	100	2,006.92 ns	29.358 ns	26.025 ns	2,011.73 ns	1,962.37 ns	2,050.82 ns	1.00	Base	0.00	-	-	-	-	NA

ToDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	9,776.74 ns	168.881 ns	149.708 ns	9,747.11 ns	9,596.95 ns	10,043.39 ns	0.98	Same	0.02	3.6833	0.3877	-	31016 B	1.00
ToDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	10,041.68 ns	178.905 ns	167.348 ns	9,997.95 ns	9,819.95 ns	10,373.81 ns	1.00	Base	0.00	3.6694	0.4032	-	31016 B	1.00

ToImmutableDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	281,817.08 ns	4,379.124 ns	4,300.886 ns	281,971.82 ns	275,266.78 ns	288,499.65 ns	1.04	Same	0.03	6.9444	1.1574	-	64097 B	1.00
ToImmutableDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	272,101.95 ns	5,216.817 ns	5,357.287 ns	270,768.10 ns	266,252.05 ns	285,728.56 ns	1.00	Base	0.00	7.5431	2.1552	-	64097 B	1.00

TryGetValue_True_Dictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	17,205.75 ns	183.564 ns	162.725 ns	17,180.39 ns	16,956.92 ns	17,508.42 ns	0.98	Same	0.02	-	-	-	-	NA
TryGetValue_True_Dictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	17,615.34 ns	196.353 ns	183.669 ns	17,640.08 ns	17,242.77 ns	17,890.94 ns	1.00	Base	0.00	-	-	-	-	NA

TryGetValue_True_ImmutableDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	65,528.70 ns	303.425 ns	253.374 ns	65,455.07 ns	65,180.80 ns	66,062.89 ns	0.99	Same	0.01	-	-	-	-	NA
TryGetValue_True_ImmutableDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	1000	66,317.31 ns	919.599 ns	860.194 ns	65,766.51 ns	65,670.49 ns	68,352.98 ns	1.00	Base	0.00	-	-	-	-	NA

ToDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	135,225.46 ns	1,934.785 ns	1,809.799 ns	134,627.07 ns	132,521.68 ns	137,873.59 ns	1.07	Same	0.04	50.0000	46.7391	45.1087	283324 B	1.00
ToDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	126,728.45 ns	3,881.702 ns	4,470.174 ns	126,718.90 ns	117,977.22 ns	134,411.62 ns	1.00	Base	0.00	46.4876	42.8719	41.8388	283336 B	1.00

ToImmutableDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	3,905,016.98 ns	64,558.467 ns	60,388.030 ns	3,887,075.00 ns	3,836,512.50 ns	4,007,631.25 ns	1.00	Same	0.02	62.5000	46.8750	-	640108 B	1.00
ToImmutableDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	3,921,738.06 ns	46,705.911 ns	41,403.573 ns	3,921,446.88 ns	3,879,031.25 ns	4,003,846.88 ns	1.00	Base	0.00	62.5000	46.8750	-	640108 B	1.00

TryGetValue_True_Dictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	239,574.73 ns	3,271.035 ns	2,731.463 ns	240,082.88 ns	233,648.37 ns	243,980.29 ns	1.00	Same	0.01	-	-	-	-	NA
TryGetValue_True_Dictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	239,909.95 ns	2,255.089 ns	1,999.078 ns	239,680.77 ns	235,758.37 ns	243,502.01 ns	1.00	Base	0.00	-	-	-	-	NA

TryGetValue_True_ImmutableDictionary	Job-ZWELZX	\runtime\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	1,116,305.32 ns	5,426.525 ns	4,531.395 ns	1,114,173.66 ns	1,113,416.52 ns	1,127,808.48 ns	0.99	Same	0.01	-	-	-	-	NA
TryGetValue_True_ImmutableDictionary	Job-KUEFVA	\runtime_baseline\artifacts\bin\testhost\net8.0-windows-Release-x64\shared\Microsoft.NETCore.App\8.0.0\CoreRun.exe	10000	1,133,305.93 ns	16,927.154 ns	15,005.481 ns	1,127,919.87 ns	1,121,172.32 ns	1,168,315.62 ns	1.00	Base	0.00	-	-	-	-	NA

In the JustifiedSubstringComparer, uses the current Slicer

Author:	IDisposable
Assignees:	-
Labels:	`area-System.Collections`, `community-contribution`
Milestone:	-

IDisposable · 2023-07-12T08:31:00Z

The Slicer does the left/right based on the sign of the Index value now, which should JIT down better.
I really wish that String.AsSpan understood the use of -1 start intrinsically as string.Length - 1... that would make the ternary unneeded.

IDisposable · 2023-07-12T08:38:05Z

Here's a real improvement. We do the math for setting a negative index (e.g. from the right side) starting with count characters from the right (as before). Then on line 81 we keep decrementing comparer.Index as we go on moving the "cursor" left.

IDisposable · 2023-07-21T06:08:22Z

This ternary is the sole remaining conditional jump in the hot loop, but there's no good way to avoid that simultaneous avoiding delegate overhead so make it as simple as possible. The number of jumps (old vs. new) is identical, but this is a tiny tiny block of JITtable goodness.

I have tried running this as a jumpless method body, but it makes little difference and is harder to grok; passing fromRight = 0 for left, or fromRight = 1 for right which requires the SubstringComparers to carry the left/right multiplier with them (so more state...):
publicstaticReadOnlySpan<char>Slicer(thisstrings,bytefromRight,intindex,intcount)=>s.AsSpan((s.Length*fromRight)+index), count);
Also, if we COULD swap the HashSet<string>'s comparer out for left vs. right the we could just have that knowledge embedded with a trait and thus fully jumpless, but that would require allocating two HashSet<string>s which might be an allocation regression nobody wants :(

I did something like that in PR #89689 which is a huge win... since we can't swap the comparer, I ended up creating both a left and right HashSet with backing comparer that "hard codes" the left/right logic. HUGE WINS, see that PR.

IDisposable · 2023-07-27T23:26:21Z

We need to re-slice the string again here. It would be awesome if we could have a HashSet<ReadOnlySpan<char> but that's not going to happen as those would be structs not objects.

The slicing is really only changed once per Count, so move the IsLeft-dependent logic into `Slicer` method and eliminate the `GetSpan` delegate. Changed to also pass the already-computed `set` of unique substrings to the `CreateAnalysisResults` method, so we don't recompute the slices twice. In order than either the set or the original `uniqueStrings` can be passed, swapped that argument for the `Analyze` method to take the `uniqueStrings` as a `string[]` (which it already is at all call-sites).

Subtle bug in that the entire string is being placed in the set, not the span.

Since we are working with the same set of input strings in each strategy there's no reason to take the length every time we make an attempt (per count, both left and right justified). Hoist the calculation of the acceptable number of collisions out to the top, do it once, and pass that number into the `HasSufficientUniquenessFactor` method for it to (locally) use up.

Benchmarks ever so slightly better.

Looks like the overhead of IEnumerable<string> is not worth the savings for the benchmark test data. Perhaps it would matter less if we were freezing more strings, but not likely

IDisposable · 2023-07-30T07:24:32Z

Performance tests (note, PR #89689 wipes the floor on this, so we should merge that instead)

Baseline is the main as of d5c4a4e
Faster Freeze is the code in this which shows between a 1%-3% performance improvement and unchanged allocation

BenchmarkDotNet=v0.13.2.2052-nightly, OS=Windows 11 (10.0.22631.2115)
Intel Core i7-10875H CPU 2.30GHz, 1 CPU, 16 logical and 8 physical cores
.NET SDK=8.0.100-preview.7.23322.33
[Host] : .NET 8.0.0 (8.0.23.32106), X64 RyuJIT AVX2
Job-PMFJSX : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT AVX2
Job-XUZNBJ : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT AVX2
Job-ORKLIM : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT AVX2
PowerPlanMode=00000000-0000-0000-0000-000000000000 Arguments=/p:EnableUnsafeBinaryFormatterSerialization=true IterationTime=250.0000 ms MaxIterationCount=20 MinIterationCount=15 WarmupCount=1

Method	Job	Toolchain	Count	Mean	Error	StdDev	Median	Min	Max	Ratio	MannWhitney(2ms)	RatioSD	Gen0	Gen1	Gen2	Allocated	Alloc Ratio
ToFrozenDictionary	Job-XUZNBJ	Baseline	10	1,271.2 ns	24.41 ns	28.11 ns	1,275.2 ns	1,216.0 ns	1,302.7 ns	1.00	Base	0.00	0.2055	-	-	1.68 KB	1.00
ToFrozenDictionary	Job-ORKLIM	Faster Freeze	10	1,246.0 ns	27.06 ns	31.17 ns	1,263.2 ns	1,194.8 ns	1,283.6 ns	0.98	Same	0.02	0.2033	-	-	1.67 KB	1.00

ToFrozenDictionary	Job-XUZNBJ	Baseline	100	7,568.4 ns	168.25 ns	193.76 ns	7,598.1 ns	7,197.6 ns	7,828.9 ns	1.00	Base	0.00	1.4281	0.0304	-	11.83 KB	1.00
ToFrozenDictionary	Job-ORKLIM	Faster Freeze	100	7,523.3 ns	156.77 ns	180.54 ns	7,583.8 ns	7,023.0 ns	7,818.5 ns	0.99	Same	0.03	1.4343	0.0305	-	11.82 KB	1.00

ToFrozenDictionary	Job-XUZNBJ	Baseline	1000	70,430.6 ns	1,377.38 ns	1,586.20 ns	70,729.1 ns	67,759.9 ns	73,232.6 ns	1.00	Base	0.00	11.3147	2.6940	-	92.64 KB	1.00
ToFrozenDictionary	Job-ORKLIM	Faster Freeze	1000	68,147.0 ns	1,356.55 ns	1,507.80 ns	68,636.0 ns	64,592.7 ns	69,908.1 ns	0.97	Same	0.02	11.1229	2.6483	-	92.63 KB	1.00

ToFrozenDictionary	Job-XUZNBJ	Baseline	10000	1,144,862.8 ns	21,895.81 ns	20,481.36 ns	1,150,661.8 ns	1,108,326.4 ns	1,179,999.3 ns	1.00	Base	0.00	145.8333	145.8333	145.8333	904.43 KB	1.00
ToFrozenDictionary	Job-ORKLIM	Faster Freeze	10000	1,131,728.1 ns	21,741.06 ns	19,272.89 ns	1,134,184.4 ns	1,105,237.5 ns	1,158,713.3 ns	0.99	Same	0.03	148.4375	148.4375	148.4375	904.42 KB	1.00

IDisposable · 2023-07-30T07:28:40Z

Did much better in PR #89689

ghost added community-contribution Indicates that the PR has been added by a community member area-System.Collections labels Jul 7, 2023

IDisposable commented Jul 7, 2023
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Comment threadsrc/libraries/System.Collections.Immutable/src/System/Collections/Frozen/String/KeyAnalyzer.cs Outdated

IDisposable force-pushed the faster-freeze-strings branch 5 times, most recently from 00e52d1 to d9d188bCompare July 12, 2023 07:41

IDisposable commented Jul 12, 2023
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