Program - 2021.2 English

Vitis Unified Software Platform Documentation: Application Acceleration Development (UG1393)

Document ID
UG1393
ft:locale
English (United States)
Release Date
2021-12-15
Version
2021.2 English

The host and kernel code are compiled separately to create separate executable files: the host program executable and the FPGA binary (.xclbin). When the host application runs, it must load the .xclbin file using the clCreateProgramWithBinary API.

The following code example shows how the standard OpenCL API is used to build the program from the .xclbin file.

unsigned char *kernelbinary;
char *xclbin = argv[1];

printf("INFO: loading xclbin %s\n", xclbin);
 
int size=load_file_to_memory(xclbin, (char **) &kernelbinary);
size_t size_var = size; 

cl_program program = clCreateProgramWithBinary(context, 1, &device_id, 
					 &size_var,(const unsigned char **) &kernelbinary, 
					 &status, &err);

// Function 
int load_file_to_memory(const char *filename, char **result)
{
  uint size = 0;
  FILE *f = fopen(filename, "rb");
  if (f == NULL) {
    *result = NULL;
    return -1; // -1 means file opening fail
  }
  fseek(f, 0, SEEK_END);
  size = ftell(f);
  fseek(f, 0, SEEK_SET);
  *result = (char *)malloc(size+1);
  if (size != fread(*result, sizeof(char), size, f)) {
    free(*result);
    return -2; // -2 means file reading fail
  }
  fclose(f);
  (*result)[size] = 0;
  return size;
}

The example performs the following steps:

  1. The kernel binary file, .xclbin, is passed in from the command line argument, argv[1].
    Tip: Passing the .xclbin through a command line argument is one approach. You can also hardcode the kernel binary file in the host program, define it with an environment variable, read it from a custom initialization file, or another suitable mechanism.
  2. The load_file_to_memory function is used to load the file contents in the host machine memory space.
  3. The clCreateProgramWithBinary API is used to complete the program creation process in the specified context and device.