# Binary inputs format

This section describes how to use `clCreateProgramWithBinary` with the POCL implementation of OpenCL.

As mentioned in the khronos documentation, the parameter `binaries` of `clCreateProgramWithBinary` can consist of either or both of device-specific code and/or implementation-specific intermediate representation.

In POCL, both representations can be used.

## Implementation-specific intermediate representation

POCL implementation of `clCreateProgramWithBinary` enables the user to create a program from a LLVM IR binary. This file needs to be one instance of the kernel, compiled as a OpenCL-C file (`-x cl`). POCL provides no tool to generate such a file.

## Device-specific representation

POCL implementation also enables the user to create a program from a device-specific binary file. The benefit of this method is that the run of your opencl code will not make any call to the compiler.

To generate this file, use the POCL tool `poclcc`.

    ./poclcc -o my_kernel.pocl my_kernel.cl

This tools gets the binary from the OpenCL function `clGetProgramInfo`, and then dump it without any modifications.

`poclcc` can take several parameters to choose for which device you what to compile your kernel, and to specify some specific build options. If you want to see the complete list, run `./poclcc -h`

When `poclcc` generates a binary file, it doesn’t have enough information to generate a code as optimized as it would have been if it has been created from source, build and enqueued in the same OpenCL code.

Here is an example on how to create a program from a file:

    int main(void)
    {
      char *binary;
      size_t binary_size;
      FILE *f;

      f = fopen("youfile", "r"); // LLVM IR file or POCLCC binary file

      fseek(f, 0, SEEK_END);
      binary_size = ftell(f);
      rewind(f);

      binary = malloc(binary_size);
      fread(binary, 1, binary_size, f);

      fclose(f);

      cl_platform_id platform_id;
      cl_device_id device_id;
      cl_context context;
      cl_program program;

      clGetPlatformIDs(1, &platform_id, NULL);
      clGetDeviceIDs(platform_id, CL_DEVICE_TYPE_DEFAULT, 1, &device_id, NULL);
      context = clCreateContext(0, 1, &device_id, NULL, NULL, NULL);

      program = clCreateProgramWithBinary(context, 1, &device_id, &binary_size, &binary, NULL, NULL);

      return 0;
    }