Run the SYCL seed finding tests

List available devices

We can list available platforms and devices with clinfo:

[bash][atspot01]:build > clinfo
    Number of platforms                               3
    Platform Name                                   Intel(R) OpenCL
    Platform Vendor                                 Intel(R) Corporation
    Platform Version                                OpenCL 2.1 LINUX

This is useful to decide which device we want to generate binaries for (because we need to give that to CMake). Note, that this would not only list OpenCL, but also CUDA devices.

We can install clinfo from our packet manager.


The SYCL seed finding implementation includes extensions from DPC++, so the code should be compiled with a dpcpp compiler. It can be cloned and built from the Intel LLVM github repository, or it could also be downloaded and installed from the oneAPI website.

CMake should inform us whether our compiler is SYCL compatible.

-- Checking if /atlas/software/intel/clang/12.0.0-2020-08-24/x86_64-ubuntu1804-gcc8-opt/bin/clang++ is SYCL capable... success
-- Checking for available SYCL target(s)...
--   - Found target: nvptx64-nvidia-cuda-sycldevice
-- Checking for available SYCL target(s)... done

Building with CMake

During the CMake configuration the flag ACTS_BUILD_PLUGIN_SYCL=on needs to be set. CMake will check whether our compiler is SYCL compatible and will look for available SYCL target architectures.

By default, SPIR 64-bits targets are looked for, but this can be configured with the SYCL_POSSIBLE_TARGETS variable. For example, to target CUDA backends, we should set this variable to nvptx64-nvidia-cuda-sycldevice.

# Figure out which SYCL target platforms are available.
set( SYCL_POSSIBLE_TARGETS "spir64-unknown-unknown-sycldevice"

Also, by setting the variable SYCL_SEARCH_SUPPORT_LIBRARIES it is possible to specify support libraries or object files that are needed for execution on a specific target. Missing object files cause a runtime error.

Trying the code

We can build the unit test ActsUnitTestSeedfinderSycl for this purpose (actually, this is not a unit test). The test compares the results of the CPU and SYCL seed finding algorithm in terms of speed and precision.

It takes the following command-line options:

Allowed options:
-h [ --help ]           Print usage message.
-f [ --FILE ] arg       Provide path for input file.
-n [ --NUM ] arg (=500) Number of groups to iterate in seed finding.
-d [ --DEVICE ] arg     Provide a substring of the preferred device.
-l [ --LIST ]           List available SYCL platforms and devices.
-G [ --GPU ]            Execute code only on gpu. Default is 0.
-a [ --ALL ]            Analyze all groups. Default is 0.
-m [ --MATCH ]          Count seed matches. Default is 0.

We can select the preferred device by the -d option, or we could also set the SYCL_BE environment variable.

By setting the environment variable SYCL_BE we can alter the behavior of the SYCL default_selector For example by setting it to PI_CUDA it forces the usage of the CUDA backend (if available). Similarly PI_OPENCL forces the usage of the OpenCL backend.

We have to provide an input file with the -f flag. The input file should have a predefined format:

[bash][atspot01]:build > head /atlas/acts_data/atlas_seeds/pu200/evt10.txt
    lxyz 1 -35.4702 -10.973 -346 0.05 0.1
    lxyz 1 -37.5198 -12.2698 -383 0.05 0.1
    lxyz 1 -39.7144 -13.9292 -423 0.05 0.1
    lxyz 1 -41.723 -16.0801 -470 0.05 0.1
    lxyz 1 -44.332 -18.1633 -525 0.05 0.1

Numbers correspond to layer, x, y, z coordinates, R, and Z variances (?).

In the end, we should see something like this:

[bash][atspot01]:build > SYCL_BE=PI_CUDA bin/ActsUnitTestSeedfinderSycl -f /atlas/acts_data/atlas_seeds/pu200/evt10.txt -m
    11:48:57    QueueWrapper   INFO      Running on: GeForce RTX 2060
    read 360734 SP from file /atlas/acts_data/atlas_seeds/pu200/evt10.txt
    Preparation time: 0.637518
    Analyzed 260 groups for CPU
    Analyzed 260 groups for SYCL

    ------------------------- Time Metric -------------------------
                 Device:        CPU       SYCL  Speedup/ Agreement
               Time (s):  13.316532   1.733498            7.681883
            Seeds found:     171516     171516           99.950447