Improve build time of Q# standard library and its tests

[vadym-kl]

Describe the enhancement request

Currently building Q# Standard Library takes 55 seconds and building it together with tests takes 01:27. This might not seem like a long time for a language's standard library to build, however the number of lines of code in Q# standard library excluding comments and blank lines is 5303 ( measured for commit 55df2709294f27a55f286bab799d60ae81e829d3 ). Including tests there are 8376 lines of Q# code.

To Reproduce

For libraries build time:

git clone https://github.com/microsoft/QuantumLibraries.git
cd .\QuantumLibraries\Standard\src\
dotnet restore
dotnet build --no-restore

For tests

cd ..\tests\
dotnet restore
dotnet build --no-restore

Expected behavior

One would expect compiling around 5000 lines of Q# code into C# to be at least comparable in speed to compiling 5000 lines of C# code. Q# is a much simpler language than C# if you look at its syntax and type system, so one would expect that compiler for it should be at least as fast as C#.

System information

• OS: Windows
• .NET Core Version: 3.1.201
• Build is run on a dedicated SSD Samsung SSD 960 EVO 500 GB, separate from the SSD on which Windows is installed
• CPU: Intel(R) Core(TM) i7-7700T CPU @ 2.90GHz set to full performance
• 32 GB RAM

Additional context

Measuring number of lines excluding blank lines and comments

To count the number of lines we used cloc with the following language definition file:

Q#
    filter rm_comments_in_strings " // 
    filter call_regexp_common C++
    3rd_gen_scale 1.36
    extension qs
    end_of_line_continuation \\$

cloc can be installed on windows with choco install cloc.

See video showing build process. Notice that the build does not take full advantage of available memory and processor.

[bettinaheim]

@vadym-kl Could you please add

<PropertyGroup>
  <AdditionalQscArguments>--perf path</AdditionalQscArguments>
</PropertyGroup>

to the project, build it, and post the content of the file in path? That will give us additional information regarding where the time is spent.

[bettinaheim]

Some improvements: https://github.com/microsoft/qsharp-compiler/pull/935

[billti]

Is this still an issue? I just repeated the initial steps of building /Standard/src (with the --perf path addition) and the entire build took 21.6 seconds, with the actual build step being a touch under 15 seconds (full log below).

This is on my MSI laptop. While admittedly a nice laptop, that doesn't seem like an egregious amount of time for a clean build of the standard library.

If this is still unacceptable, let's define a clear goal to aim for, else we should close this bug. (Parity with C# isn't a realistic goal, as they have person-decades of investment in that compiler).

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  "OverallCompilation.Build": 14965,
  "OverallCompilation.OutputGeneration": 310,
  "OverallCompilation.OutputGeneration.BinaryGeneration": 4,
  "OverallCompilation.OutputGeneration.SyntaxTreeSerialization": 305,
  "OverallCompilation.ReferenceLoading": 169,
  "OverallCompilation.ReferenceLoading.HeaderAttributesLoading[21]": 3,
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  "OverallCompilation.ReferenceLoading.HeaderAttributesLoading[19]": 1,
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}