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SYCL Academy

Exercise 2: Configuring a Queue

In this first exercise you will learn:

  • How to construct a queue using a device selector.
  • How to define and use your own device selector.
  • How to query information about a device.

The first thing you must do in a SYCL application is to construct a queue that will enqueue work, and a queue is associated with a single device to which it enqueues work. The simplest way to construct a queue in SYCL is to pass it a device selector, that is then used to choose a device from all the devices available in your system.

1.) Create a queue using the default selector

Construct a SYCL queue using the default constructor and try printing the name of the device.

Remember the device associated with a queue can be retrieved using the get_device member function and information about a device can be queried using the get_info member function template.

2.) Try other device selectors

Replace the default selector with one of the other standard device selectors that are provided by SYCL (see SYCL 1.2.1 specification, sec. 4.6.1.2) and see which device those choose.

3.) Create your own device selector

Create a device selector using the template below, implementing the function call operator, using various device and platform info queries like the one we used earlier to query the device name (see SYCL 1.2.1 specification, sec. 4.6.4.2) and then use that device selector in the queue constructor:

class my_device_selector : public device_selector {
 public:
  my_device_selector() {}

  virtual int operator()(const device &device) const { }
};

Remember the platform associated with a device can be retrieved using the get_platform member function.

Remember that the value returned from the device selector's function call operator will represent the score for each device, and a device with a negative score will never be chosen.

Build And Execution Hints

For For DPC++ (using the Intel DevCloud):

dpcpp -o sycl-ex-2 -I../External/Catch2/single_include ../Code_Exercises/Exercise_2_Configuring_a_Queue/source.cpp

In Intel DevCloud, to run computational applications, you will submit jobs to a queue for execution on compute nodes, especially some features like longer walltime and multi-node computation is only abvailable through the job queue. Please refer to the example.

So wrap the binary into a script job_submission and run:

qsub job_submission

For ComputeCpp:

cmake -DSYCL_ACADEMY_USE_COMPUTECPP=ON -DSYCL_ACADEMY_INSTALL_ROOT=/insert/path/to/computecpp ..
make Exercise_2_source
./Code_Exercises/Exercise_2_Configuring_a_Queue/Exercise_2_source

For hipSYCL:

# Add -DHIPSYCL_GPU_ARCH=<arch> to the cmake arguments when compiling for GPUs.
# <arch> is e.g. sm_60 for NVIDIA Pascal GPUs, gfx900 for AMD Vega 56/64, and gfx906 for Radeon VII.
cmake -DSYCL_ACADEMY_USE_HIPSYCL=ON -DSYCL_ACADEMY_INSTALL_ROOT=/insert/path/to/hipsycl -DHIPSYCL_PLATFORM=<cpu|cuda|rocm> ..
make Exercise_2_source
./Code_Exercises/Exercise_2_Configuring_a_Queue/Exercise_2_source

alternatively, without cmake:

cd Code_Exercises/Exercise_2_Configuring_a_Queue
HIPSYCL_PLATFORM=<cpu|cuda|rocm> HIPSYCL_GPU_ARCH=<arch-when-compiling-for-gpu> /path/to/hipsycl/bin/syclcc -o sycl-ex-2 -I../../External/Catch2/single_include source.cpp
./sycl-ex-2