Troubleshooting SYCL Binary Execution With ASE And UR_RESULT_ERROR_INVALID_BINARY

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When co-simulating a SYCL-based FPGA application using the Altera Simulation Environment (ASE), it's crucial to understand which binary to execute. This article addresses the common issue of encountering the UR_RESULT_ERROR_INVALID_BINARY error and provides a comprehensive guide to running SYCL binaries with ASE effectively.

Understanding the Problem: UR_RESULT_ERROR_INVALID_BINARY

The error message Native API failed. Native API returns: 7 (UR_RESULT_ERROR_INVALID_BINARY) indicates that the binary you are attempting to execute is not in the expected format or is not compatible with the simulation environment. This typically arises when you try to directly run the .fpga binary generated by the SYCL compiler within the ASE setup.

Key Concepts

Before diving into the solution, let's clarify some key concepts:

  • SYCL: A high-level programming model for heterogeneous computing, often used for targeting FPGAs.
  • ASE (Altera Simulation Environment): A simulation environment for Intel FPGAs that allows you to co-simulate hardware and software components.
  • .fpga Binary: This is the hardware binary generated by the Intel oneAPI DPC++/C++ Compiler, intended for programming the FPGA. It is not directly executable in the host environment during co-simulation.
  • Host Application: This is the software application written in SYCL (or another language) that interacts with the FPGA. It's compiled for the host processor and orchestrates the data transfer and kernel execution on the FPGA.

The Root Cause

The UR_RESULT_ERROR_INVALID_BINARY error occurs because the .fpga binary is designed to be loaded onto the FPGA hardware. During co-simulation with ASE, you're not directly programming the FPGA; instead, you're running a simulation of the FPGA within the ASE environment. The host application needs to interact with the ASE simulator, not directly with the .fpga file.

The Correct Approach: Running the Host Application

The key to successful co-simulation with ASE is to execute the host application, not the .fpga binary. The host application is responsible for:

  1. Initializing the SYCL runtime.
  2. Selecting the appropriate SYCL device (in this case, the ASE simulator).
  3. Loading the kernel (which may involve the .fpga binary indirectly).
  4. Transferring data to the FPGA (or the simulator).
  5. Launching the kernel execution.
  6. Retrieving results from the FPGA (or the simulator).

Steps to Run the Host Application with ASE

Let's break down the steps to correctly run your SYCL application with ASE:

  1. Set up the ASE Environment: As shown in the original problem description, you've already started the ASE hardware-side simulator using run-ase.sh. This script sets up the necessary environment for the simulation.

    $ ./ase/run-ase.sh /hls-samples/Tutorials/Features/ac_int ofs_my_board

  2. Export ASE_WORKDIR: The run-ase.sh script provides instructions on setting the ASE_WORKDIR environment variable. This variable tells the host application where the ASE simulation environment is located. It's crucial to set this variable in the same terminal where you'll run the host application.

    export ASE_WORKDIR=xxx # Replace xxx with the actual path
    • Importance of ASE_WORKDIR: The ASE_WORKDIR environment variable is critical for the host application to locate and communicate with the ASE simulator. Without this, the application won't be able to find the simulation environment, leading to errors. Make sure you set this variable correctly in the terminal where you intend to run your host application.

  3. Set FPGA Emulation Environment Variables: In addition to ASE_WORKDIR, you may need to set other environment variables to configure the SYCL runtime to use the ASE simulator. The most common ones are:

    export CL_CONTEXT_MPSIM_DEVICE_INTELFPGA=1
export INTELFPGA_SIM_DEVICE_SPEC_DIR=ac_int.fpga.prj
    • CL_CONTEXT_MPSIM_DEVICE_INTELFPGA=1: This variable tells the SYCL runtime to use the multi-process simulator (MPSim) for Intel FPGAs. This is essential for running with ASE.
    • INTELFPGA_SIM_DEVICE_SPEC_DIR=ac_int.fpga.prj: This variable specifies the directory containing the device specification files for the simulator. It's usually the directory where the .fpga binary and related files are located. This ensures that the simulator knows the details of the FPGA design being simulated.

  4. Locate and Run the Host Executable: The host application is a separate executable that you compile alongside your SYCL kernel code. It's typically named something like host or main, depending on your project structure. You need to find this executable and run it.

    cd <path_to_host_executable>
./host # Or whatever the name of your host executable is
    • Identifying the Host Executable: The host executable is the compiled version of your C++, SYCL, or other host-side code. It's what orchestrates the FPGA interaction. If you're unsure where it is, check your project's build directory or refer to your project's build instructions. It's crucial to execute the host application, as it's the bridge between your software and the simulated FPGA hardware.

  5. Compilation: To ensure correct execution within the ASE environment, it's recommended to compile your host application without the -fintelfpga flag. This flag is intended for compiling code that will run on actual FPGA hardware. When using ASE, you want to target the simulation environment, which requires a different compilation approach.

    icpx <your_host_code.cpp> -o host
    • Compiling for Simulation: When working with ASE, the compilation process for your host application is slightly different than when targeting real FPGA hardware. By omitting the -fintelfpga flag, you ensure that the code is compiled to run on your host machine's processor, which then interacts with the ASE simulator. This is a key distinction to remember for successful co-simulation.

Example Scenario

Let's assume your project structure looks like this:

my_project/
├── src/
│   ├── kernel.cpp # SYCL kernel code
│   └── host.cpp   # Host application code
├── build/
│   └── host       # Compiled host executable
└── ase/
    └── run-ase.sh

Here's how you would run the co-simulation:

  1. Run run-ase.sh:

    cd my_project/ase
./run-ase.sh ../src ofs_my_board

  2. Set ASE_WORKDIR and other environment variables:

    export ASE_WORKDIR=/path/to/ase_sim-my_board-6t1pa9 # Replace with actual path
export CL_CONTEXT_MPSIM_DEVICE_INTELFPGA=1
export INTELFPGA_SIM_DEVICE_SPEC_DIR=../build

  3. Run the host application:

    cd my_project/build
./host

Troubleshooting Tips

  • Double-Check Environment Variables: The most common cause of issues with ASE co-simulation is incorrect environment variable settings. Make sure ASE_WORKDIR, CL_CONTEXT_MPSIM_DEVICE_INTELFPGA, and INTELFPGA_SIM_DEVICE_SPEC_DIR are set correctly.
  • Examine the ASE Output: The run-ase.sh script and the ASE simulator itself print valuable debugging information. Pay close attention to any warnings or errors in the output.
  • Review the Host Application Code: Ensure that your host application correctly initializes the SYCL runtime, selects the simulator device, and handles data transfers and kernel execution.
  • Check File Paths: Verify that all file paths used in your application and environment variables are correct.

In Summary: Running SYCL Applications with ASE

The UR_RESULT_ERROR_INVALID_BINARY error when working with ASE and SYCL signifies that you're attempting to execute the .fpga binary directly, which is not the correct procedure for co-simulation. The key takeaway is to run the host application after properly setting the necessary environment variables, including ASE_WORKDIR, CL_CONTEXT_MPSIM_DEVICE_INTELFPGA, and INTELFPGA_SIM_DEVICE_SPEC_DIR. By following the steps outlined in this article and paying close attention to the troubleshooting tips, you can effectively co-simulate your SYCL-based FPGA applications using ASE and avoid this common pitfall.

Key Takeaways

  • Never run the .fpga binary directly in ASE co-simulation. This is the most critical point to remember.
  • Always execute the host application. The host application acts as the intermediary between your software and the simulated FPGA.
  • Set ASE_WORKDIR correctly. This environment variable is essential for the host application to find the ASE simulator.
  • Use CL_CONTEXT_MPSIM_DEVICE_INTELFPGA=1 to target the ASE simulator. This ensures that the SYCL runtime uses the simulation environment.
  • Verify INTELFPGA_SIM_DEVICE_SPEC_DIR to point to the directory containing your device specification files. This helps the simulator understand the FPGA design.
  • Compile your host application without the -fintelfpga flag when targeting ASE. This ensures compatibility with the simulation environment.
  • Pay close attention to ASE output for debugging information. The simulator's messages can provide valuable clues for troubleshooting.
  • Double-check all environment variables and file paths. Typos or incorrect paths are common sources of errors.

By adhering to these principles, you'll be well-equipped to navigate the intricacies of SYCL and ASE co-simulation, leading to successful FPGA application development and verification.

Conclusion

Successfully running SYCL binaries with ASE requires a clear understanding of the co-simulation process and the roles of different components. By focusing on executing the host application, setting the correct environment variables, and understanding the purpose of each step, you can overcome the UR_RESULT_ERROR_INVALID_BINARY error and effectively utilize ASE for your FPGA development workflow. Remember to consult the Intel oneAPI documentation and community resources for further assistance and to stay updated on best practices for SYCL and FPGA development.