Catch2-SYCL

A simple repository to demonstrate an issue I have found with unnamed SYCL kernels in Catch2 test cases with Intel's DPC++ SYCL implementation.

Prerequisites

You will need the following software available

A SYCL implementation such as
- Intel oneAPI DPC++ 2023.1.0 or newer (tested with 2023.2.0)
- Open SYCL (aka hipSYCL) (tested with 0.9.4)
CMake 3.20.5 or newer (tested with 3.27.1)

Build instructions

First make sure you have set up your environment correctly with the prerequisites listed above available (e.g. modules loaded/setvars.sh script sourced).

Clone the repository:

git clone https://github.com/mirenradia/Catch2-SYCL.git

Next create a build directory and change into it:

mkdir Catch2-SYCL/build && cd Catch2-SYCL/build

If you want to use Open SYCL instead of Intel DPC++, comment out the line
```
find_package(IntelSYCL REQUIRED)
```
and uncomment the line
```
find_package(hipSYCL REQUIRED)
```
Configure the build. For Intel DPC++, make sure you set icpx as the C++ compiler:
```
cmake -DCMAKE_CXX_COMPILER=icpx ..
```
For Open SYCL, you will need to explicitly set the HIPSYCL_TARGETS variable. You can set it as an environment variable or in the CMake configure command. For example, to target the OpenMP backend, you can do
```
cmake -DHIPSYCL_TARGETS="omp" ..
```
Finally, build the application using make:
```
make -j `nproc`
```

Running

This is a Catch2 application with two test cases (imaginatively named "Test1" and "Test2"). Catch2 provides the main() function and also allows the user to pass a plethora of flags on the command-line. For more information, do

./catch2sycl --help

By default, if no flags are passed, both test cases are run:

./catch2sycl

With Open SYCL, both test cases should pass and you should observe something like:

Randomness seeded to: xxxxxxxx
===============================================================================
All tests passed (2048 assertions in 2 test cases)

With Intel DPC++, you should find one of the test cases fails and observe output something like:

Randomness seeded to: xxxxxxxx

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
catch2sycl is a Catch2 v3.4.0 host application.
Run with -? for options

-------------------------------------------------------------------------------
Test2
-------------------------------------------------------------------------------
/home/miren/RSE/Catch2-SYCL/TestCase2.cpp:7
...............................................................................

/home/miren/RSE/Catch2-SYCL/TestCase2.cpp:37: FAILED:
  REQUIRE( shared_ptr_c[i] == 3 * i )
with expansion:
  2 == 3

===============================================================================
test cases:    2 |    1 passed | 1 failed
assertions: 1026 | 1025 passed | 1 failed

Intel DPC++ problem

The problem seems to come from the mangled names the compiler generates for both of the SYCL kernels being the same. In my case, this is something like

_ZTSZL22CATCH2_INTERNAL_TEST_0vEUlN4sycl3_V12idILi1EEEE_

(I found this by looking at the output with the SYCL_PI_TRACE=2 environment variable set.) Catch2's macros use the __COUNTER__ predefined macro to generate a "unique" name for the test case function by default (it can be configured to also use the line number instead, but this would have the same problem). Unfortunately, this counter seems to only increase within each separate invocation to the preprocessor thus test cases defined in different source files (i.e. non-headers) can have the same name. This confuses the DPC++ compiler/linker/runtime which links the kernel invocation on the host to the same device kernel code in both cases leading to test failure.