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Refactor multiply operation for better performance in 2 Commands.Utility functions#14148

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anmenaga merged 5 commits into
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xtqqczze:eliminate-mul
Dec 8, 2020
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Refactor multiply operation for better performance in 2 Commands.Utility functions#14148
anmenaga merged 5 commits into
PowerShell:masterfrom
xtqqczze:eliminate-mul

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@xtqqczze xtqqczze commented Nov 19, 2020 •
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PR Summary

Factor out multiply operation for slightly more readable code.

Replace all instances of x * (y ? 1 : -1) with y ? x : -x.

PR Context

As shown in following micro-benchmark results, these changes do not worsen performance, there is in fact a very small absolute gain.

| Method |      Mean |     Error |    StdDev |    Median | Code Size | Gen 0 | Gen 1 | Gen 2 | Allocated |
|------- |----------:|----------:|----------:|----------:|----------:|------:|------:|------:|----------:|
|    Mul | 0.6288 ns | 0.0518 ns | 0.0836 ns | 0.5843 ns |      25 B |     - |     - |     - |         - |
|    Neg | 0.0358 ns | 0.0275 ns | 0.0496 ns | 0.0000 ns |      16 B |     - |     - |     - |         - |

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@ghost ghost assigned anmenaga Nov 19, 2020
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iSazonov commented Nov 20, 2020

@xtqqczze Not for the PR: could you please fix !(this is pattern in ProviderBase.cs.

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iSazonov commented Nov 20, 2020 •
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there is in fact a very small gain.

0.0358 ns vs 0.6288 ns small?

It seems there are other places where we use the multiply.

@iSazonov iSazonov added CL-CodeCleanup Indicates that a PR should be marked as a Code Cleanup change in the Change Log CL-Performance Indicates that a PR should be marked as a performance improvement in the Change Log and removed CL-CodeCleanup Indicates that a PR should be marked as a Code Cleanup change in the Change Log labels Nov 20, 2020
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xtqqczze commented Nov 20, 2020

there is in fact a very small gain.

0.0358 ns vs 0.6288 ns small?

Large relative gain but small absolute gain (in micro-benchmark).

It seems there are other places where we use the multiply.

This PR replaces all instances of the x * (y ? 1 : -1) pattern.

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iSazonov commented Nov 20, 2020

This PR replaces all instances of the x * (y ? 1 : -1) pattern.

See private object Compare(object objValue, object statMinOrMaxValue, bool isMin) in Measure-Object.
I guess we have others. I don't ask you to find all and fix but it would be great.

@xtqqczze xtqqczze force-pushed the eliminate-mul branch 2 times, most recently from 9a42619 to 154e218 Compare November 20, 2020 16:09
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anmenaga commented Nov 20, 2020

How the measurements were done / results table in PR Context was created?

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xtqqczze commented Nov 21, 2020

How the measurements were done / results table in PR Context was created?

Using BenchmarkDotNet:

...
        bool _ascendingOrder = false;
        int result = 7;

        [Benchmark]
        public int Mul()
        {
            return result * (_ascendingOrder ? 1 : -1);
        }

        [Benchmark]
        public int Neg()
        {
            return _ascendingOrder ? result : -result;
        }
...

Not the most realistic benchmark, but the results do show performance is not harmed by the changes.

iSazonov
iSazonov reviewed Nov 24, 2020
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Comment thread src/Microsoft.PowerShell.Commands.Utility/commands/utility/Measure-Object.cs Outdated
@xtqqczze xtqqczze changed the title Simplify complex return statement Refactor multiply operation Nov 24, 2020
@xtqqczze xtqqczze mentioned this pull request Nov 24, 2020
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@ghost ghost added the Review - Needed The PR is being reviewed label Dec 1, 2020
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ghost commented Dec 1, 2020

This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author

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xtqqczze commented Dec 1, 2020

@iSazonov Please could you approve changes.

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iSazonov commented Dec 1, 2020

@iSazonov Please could you approve changes.

I did but since the PR changes code we need more reviewers.

@ghost ghost removed the Review - Needed The PR is being reviewed label Dec 1, 2020
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anmenaga approved these changes Dec 8, 2020
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LGTM

@anmenaga anmenaga changed the title Refactor multiply operation Refactor multiply operation for better performance in 2 Commands.Utility functions Dec 8, 2020
@anmenaga anmenaga merged commit dd4e5c7 into PowerShell:master Dec 8, 2020
@xtqqczze xtqqczze deleted the eliminate-mul branch December 8, 2020 23:26
@iSazonov iSazonov added this to the 7.2.0-preview.2 milestone Dec 9, 2020
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ghost commented Dec 15, 2020

🎉v7.2.0-preview.2 has been released which incorporates this pull request.:tada:

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