[OpenMP] Add ompTest library to OpenMP

[mhalk]

Description

OpenMP Tooling Interface Testing Library (ompTest) ompTest is a unit testing framework for testing OpenMP implementations. It offers a simple-to-use framework that allows a tester to check for OMPT events in addition to regular unit testing code, supported by linking against GoogleTest by default. It also facilitates writing concise tests while bridging the semantic gap between the unit under test and the OMPT-event testing.

Background

This library has been developed to provide the means of testing OMPT implementations with reasonable effort. Especially, asynchronous or unordered events are supported and can be verified with ease, which may prove to be challenging with LIT-based tests. Additionally, since the assertions are part of the code being tested, ompTest can reference all corresponding variables during assertion.

Basic Usage

OMPT event assertions are placed before the code, which shall be tested. These assertion can either be provided as one block or interleaved with the test code. There are two types of asserters: (1) sequenced "order-sensitive" and (2) set "unordered" assserters. Once the test is being run, the corresponding events are triggered by the OpenMP runtime and can be observed. Each of these observed events notifies asserters, which then determine if the test should pass or fail.

Example (partial, interleaved)

  int N = 100000;
  int a[N];
  int b[N];

  OMPT_ASSERT_SEQUENCE(Target, TARGET, BEGIN, 0);
  OMPT_ASSERT_SEQUENCE(TargetDataOp, ALLOC, N * sizeof(int)); // a ?
  OMPT_ASSERT_SEQUENCE(TargetDataOp, H2D, N * sizeof(int), &a);
  OMPT_ASSERT_SEQUENCE(TargetDataOp, ALLOC, N * sizeof(int)); // b ?
  OMPT_ASSERT_SEQUENCE(TargetDataOp, H2D, N * sizeof(int), &b);
  OMPT_ASSERT_SEQUENCE(TargetSubmit, 1);
  OMPT_ASSERT_SEQUENCE(TargetDataOp, D2H, N * sizeof(int), nullptr, &b);
  OMPT_ASSERT_SEQUENCE(TargetDataOp, D2H, N * sizeof(int), nullptr, &a);
  OMPT_ASSERT_SEQUENCE(TargetDataOp, DELETE);
  OMPT_ASSERT_SEQUENCE(TargetDataOp, DELETE);
  OMPT_ASSERT_SEQUENCE(Target, TARGET, END, 0);

  {
    for (int j = 0; j < N; j++)
      a[j] = b[j];
  }

References

This work has been presented at SC'24 workshops, see: https://ieeexplore.ieee.org/document/10820689

Current State and Future Work

ompTest's development was mostly device-centric and aimed at OMPT device callbacks and device-side tracing. Consequentially, a substantial part of host-related events or features may not be supported in its current state. However, we are confident that the related functionality can be added and ompTest provides a general foundation for future OpenMP and especially OMPT testing. This PR will allow us to upstream the corresponding features, like OMPT device-side tracing in the future with significantly reduced risk of introducing regressions in the process.

Build

ompTest is linked against LLVM's GoogleTest by default, but can also be built 'standalone'. Additionally, it comes with a set of unit tests, which in turn require GoogleTest (overriding a standalone build). The unit tests are added to the check-openmp target.

Use the following parameters to perform the corresponding build:
LIBOMPTEST_BUILD_STANDALONE (Default: OFF)
LIBOMPTEST_BUILD_UNITTESTS (Default: OFF)

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[mhalk]

While being aware that this change is of substantial size, we chose to start the reviewing process to gather feedback.
If it is desired to provide this change in smaller chunks, please provide suggestions.

Also, please pull in other reviewers as needed.

[jplehr]

It seems we forgot to add the appropriate license statement in the source files.

[mhalk]

It seems we forgot to add the appropriate license statement in the source files.

Good catch, thanks for pointing that out. It should be corrected now :)

[jplehr]

Maybe as an additional comment, given that it may not be obvious from the initial message: This is the first part of our efforts to upstream our OMPT device-tracing support from OpenMP offloading.

[jprotze]

Am I right, that the unittests in this PR are to test omptest itself, and not some specific event sequences from the OpenMP runtime library?

[mhalk]

Am I right, that the unittests in this PR are to test omptest itself, and not some specific event sequences from the OpenMP runtime library?

Yes, correct.
Currently, these unit tests, while not exhaustive, provide some basic coverage and a starting point for further testing.