libnd4j/dev-docs/LaunchDims.md
This part of the libnd4j codebase provides a centralized way to handle CUDA launch configurations. It allows customization of launch dimensions using environment variables.
The code sets up CUDA launch configurations for a wide range of algorithms used in the libnd4j codebase. These configurations are expressed as dim3 structures, representing grid and block dimensions for launching CUDA kernels. The configurations are stored in a map, improving performance via a caching mechanism.
A significant feature of this code is the flexibility it offers, allowing users to specify custom launch dimensions through environment variables. This enables modifications of these configurations at both compile-time and runtime.
// Fetching Launch Dimensions
dim3 launchDims = getLaunchDims("matrixMultiply");
//invoke your cuda function
yourKernel<<<launchDims.y,launchDims.x,launchDims.z>>>
//This returns the blocks, threads and shared memory used for the kernel.
The launch configuration can be found in
../include/execution/cuda/LaunchDims.h
../include/execution/cuda/LaunchDims.cu
Every kernel has environment variables that work at build time and runtime. Build time is used to modify defaults. Runtime is used to override buildtime and defaults.