Troubleshooting SYCL Binaries And ASE How To Fix UR_RESULT_ERROR_INVALID_BINARY

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Introduction

This article addresses a common issue encountered when performing co-simulation with the Intel® FPGA Emulation Platform (ASE) and SYCL-based FPGA applications. Specifically, it tackles the UR_RESULT_ERROR_INVALID_BINARY error that arises when attempting to run the *.fpga binary directly. This guide provides a detailed explanation of the problem, the correct approach to running SYCL binaries within the ASE environment, and troubleshooting steps to resolve the issue.

Understanding the Problem: UR_RESULT_ERROR_INVALID_BINARY with ASE and SYCL

When developing FPGA applications using SYCL and targeting Intel® FPGAs, the ASE is a crucial tool for co-simulation. It allows developers to simulate the hardware behavior of their FPGA design in conjunction with the software application running on the host. This co-simulation environment helps identify and resolve issues early in the development cycle.

In the context of SYCL and ASE, the UR_RESULT_ERROR_INVALID_BINARY error typically indicates that the binary being executed is not the correct one for the simulation environment. The SYCL compiler generates different binaries for various execution targets, including hardware FPGA, software emulation, and the ASE. The *.fpga binary, while containing the FPGA bitstream, is not directly executable in the ASE environment. Instead, a host application needs to be executed which will then load the FPGA binary onto the ASE simulator.

The error message Native API failed. Native API returns: 7 (UR_RESULT_ERROR_INVALID_BINARY) is a clear indication of this mismatch. The ASE runtime environment expects a specific type of binary, and attempting to execute the *.fpga file directly violates this expectation. This article explains the correct approach to run your co-simulation.

The Correct Way to Run SYCL Binaries with ASE

To successfully run SYCL binaries with ASE, it’s crucial to understand the co-simulation workflow. The ASE acts as a hardware emulator, and your SYCL application needs to interact with it through a host application. Here’s the breakdown of the correct procedure:

  1. Compilation for ASE: When compiling your SYCL application for ASE, ensure that you are using the appropriate compiler flags. The compile-kernel.sh script, often generated by build systems like CMake, typically handles this. The key flag to look for is -fintelfpga -Xsno-env-check, which instructs the compiler to generate a binary compatible with the ASE. This step will generate both the *.fpga binary and a host executable.
  2. Starting the ASE Simulator: Use the run-ase.sh script (or equivalent) to start the ASE simulator. This script sets up the necessary environment variables and launches the simulation environment. The script will typically provide instructions on setting the ASE_WORKDIR environment variable. This variable is crucial for the host application to locate and communicate with the ASE simulator.
  3. Setting Environment Variables: Before running the host application, it is essential to set the environment variables as instructed by run-ase.sh. The most important variable is ASE_WORKDIR, which points to the directory where the ASE simulator is running. Other environment variables, such as CL_CONTEXT_MPSIM_DEVICE_INTELFPGA and INTELFPGA_SIM_DEVICE_SPEC_DIR, may also be necessary depending on your application and the specific ASE setup.
  4. Running the Host Application: The key step is to run the host application, not the *.fpga binary directly. The host application is the executable that you compiled alongside your SYCL kernel code. This application is responsible for loading the *.fpga binary into the ASE simulator, transferring data to and from the simulated FPGA, and orchestrating the co-simulation. The host application uses the SYCL runtime to interact with the FPGA device, which is emulated by ASE.

Step-by-Step Guide to Running SYCL Applications with ASE

Let's illustrate the correct procedure with a step-by-step guide, referencing the example provided in the original problem description:

  1. Start the ASE Simulator:
./ase/run-ase.sh /hls-samples/Tutorials/Features/ac_int ofs_my_board

This command launches the ASE simulator for the ac_int example design, targeting the ofs_my_board FPGA. The script will output instructions, including how to set the ASE_WORKDIR environment variable.

  1. Set the ASE_WORKDIR Environment Variable:
export ASE_WORKDIR=xxx # Replace 'xxx' with the actual path provided by run-ase.sh

This step is critical. The host application needs this environment variable to find the ASE simulator.

  1. Navigate to the Application Directory:

Navigate to the directory containing your compiled host application. This is usually in the build directory of your project. It's important to distinguish this directory from the directory containing *.fpga binary which is located inside the ASE working directory.

  1. Run the Host Application:

Instead of running ./ac_int.fpga, you need to run the host executable. The name of this executable depends on your project structure and build system. It’s often the same name as your project or SYCL kernel.

For example, if your project name is ac_int, the host executable might be named ac_int or ac_int_host. Run the executable like this:

./ac_int # Or ./ac_int_host, or whatever the name of your host executable is

The host application will then load the *.fpga binary into the ASE simulator and begin the co-simulation.

Troubleshooting UR_RESULT_ERROR_INVALID_BINARY and Other Common Issues

Even with the correct procedure, you might encounter issues. Here are some common problems and troubleshooting tips:

  • Incorrect ASE_WORKDIR: The most common cause of UR_RESULT_ERROR_INVALID_BINARY is an incorrectly set ASE_WORKDIR environment variable. Double-check that you have set it to the exact path provided by run-ase.sh. A typo or an outdated path can lead to this error.
  • *Running the .fpga Binary Directly: As highlighted earlier, never attempt to run the *.fpga binary directly. Always run the host application.
  • Missing Environment Variables: Ensure that all required environment variables are set. Besides ASE_WORKDIR, other variables like CL_CONTEXT_MPSIM_DEVICE_INTELFPGA and INTELFPGA_SIM_DEVICE_SPEC_DIR might be necessary. Consult the ASE documentation or the output of run-ase.sh for the specific requirements of your setup.
  • Compiler and Runtime Version Mismatch: Ensure that your compiler version and the ASE runtime are compatible. Using mismatched versions can lead to various errors, including UR_RESULT_ERROR_INVALID_BINARY.
  • Incorrect Compilation Flags: Verify that you have compiled your SYCL application with the correct flags for ASE. The -fintelfpga -Xsno-env-check flags are crucial for generating a compatible binary. Review your compile-kernel.sh script or build system configuration.
  • ASE Simulator Not Running: Confirm that the ASE simulator is running before you attempt to run the host application. The run-ase.sh script should indicate that the simulator is ready for simulation.
  • Firewall Issues: In some cases, firewalls can interfere with the communication between the host application and the ASE simulator. If you suspect this is the case, try temporarily disabling the firewall or configuring it to allow communication on the ports used by ASE.
  • Debugging with GDB: If you are still facing issues, you can use a debugger like GDB to step through your host application and identify the source of the error. This can provide valuable insights into why the binary is not loading correctly.

Example Scenario and Solution

Let's revisit the original scenario and apply the correct solution:

The user encountered UR_RESULT_ERROR_INVALID_BINARY after running ./ac_int.fpga. The mistake was attempting to execute the *.fpga binary directly.

The correct solution is to identify and run the host executable. Assuming the host executable is named ac_int_host, the user should do the following:

  1. Ensure that the ASE simulator is running, and ASE_WORKDIR is set correctly.
  2. Navigate to the directory containing ac_int_host (likely a build directory).
  3. Run ./ac_int_host.

This will initiate the co-simulation, loading the *.fpga binary into the ASE simulator and executing the SYCL application.

Conclusion

The UR_RESULT_ERROR_INVALID_BINARY error when using ASE with SYCL applications is typically a result of attempting to run the *.fpga binary directly. By understanding the co-simulation workflow and running the host application instead, you can avoid this error and successfully simulate your FPGA designs. Remember to set the ASE_WORKDIR environment variable correctly and double-check your compilation flags. This article provides a comprehensive guide to troubleshoot this issue and other common problems encountered when using ASE with SYCL. By following the steps outlined here, you can ensure a smooth and efficient co-simulation experience, accelerating your FPGA development process.