12-host-programs #

Host code is a C function compiled to an ELF object, loaded as an image on the host and launched as a GPU's kernel is. This example loads affine.c, launches it on host buffers, then over a million threads in groups that the host's cores run in parallel.

cd packages/rig/examples/12-host-programs
dune exec ./main.exe

What You'll Learn #

• Loading an object on the host: Rig.Image.load Rig.host
• The calling convention, void f(const void *params, int64_t first, int64_t end), with the buffers' host addresses in the parameters
• Launches over many groups, which the host's cores run in parallel, each call of the function given a range of whole groups
• Choosing the object for the host: Rig.arch Rig.host

Key Functions #

Function	Purpose
Image.load host obj	The image of obj, or why not
Submission.launch, submit	Run one of its functions over a grid
Image.resolve image f	Its function f, if it has one

The objects #

affine_x86_64.o and affine_aarch64.o are affine.c compiled in this directory with Homebrew clang 22.1.7. With H = -c -x c -O2 -fPIC -ffreestanding -fno-math-errno -nostdlib -fno-ident:

clang $H --target=x86_64-none-unknown-elf affine.c -o affine_x86_64.o
clang $H -ffixed-x18 --target=aarch64-none-unknown-elf affine.c -o affine_aarch64.o

-ffixed-x18 keeps the code off the register macOS and Windows reserve.

Next Steps #

Continue to 13-pool.