port-to-hpvm-c.rst

Porting a Program from C to HPVM-C

The following represents the required steps to port a regular C program into an HPVM program with HPVM-C. These steps are described at a high level; for more detail, please see hpvm-cava provided in benchmarks.

• Separate the computation that will become a kernel into its own (leaf node) function and add the attributes and target hint.
• Create a level 1 wrapper node function that will describe the thread-level parallelism (for the GPU). The node will:
  • Use the createNode[ND]() method to create a kernel node and specify how many threads will execute it.
  • Bind its arguments to the kernel arguments.
• If desired, create a level 2 wrapper node function which will describe the threadblock-level parallalism (for the GPU). This node will:
  • Use the createNode[ND]() method to create a level 1 wrapper node and specify how many threadblocks will execute it.
  • Bind its arguments to its child node's arguments.
• A root node function that creates all the top-level wrapper nodes, binds their arguments, and connects their edges.
  • Each root node represents a DFG.
• All the above node functions have the combined arguments of all the kernels that are nested at each level.
• The host code will have to include the following:
  • Initialize the HPVM runtime using the init() method.
  • Create an argument struct for each DFG and assign its member variables.
  • Add all the memory that is required by the kernel into the memory tracker.
  • Launch the DFG by calling the launch() method on the root node function, and passing the corresponding argument struct.
  • Wait for the DFG to complete execution.
  • Read out any generated memory using the request_mem() method.
  • Remove all the tracked memory from the memory tracker.