CUDA driver API equivalent for cudaSetDevice
c, cuda
Solution
You can find information about this in the Programming Guide Appendix about the Driver API, but the short version is this:
- `cuCtxCreate` acts as the first `cudaSetDevice` call (that is it creates a context on the driver context stack)
- The `cuCtxPushCurrent()` and `cuCtxPopCurrent()` pair (or `cuCtxSetCurrent` depending on which API version you are using) acts as any subsequent `cudaSetDevice` call (that is it pushes or selects a previously created context to be the active context for all subsequent API calls until the context is popped off the driver context stack or deselected)
Problem
What is the CUDA driver's API equivalent for the runtime API function `cudaSetDevice`? I was looking into the driver API and cannot find an equivalent function. What I can do is ``` cuDeviceGet(&cuDevice, device_no); cuCtxCreate(&cuContext, 0, cuDevice); ``` which is not equivalent since beside setting the device it also creates a context. The runtime API `cudaSetDevice` does not create a context per se. In the runtime API the CUDA context is created implicitly with the first CUDA call that requires state on the device. Background for this question: CUDA-aware MPI (MVAPICH2 1.8/9) initialization requires the CUDA device to be set before `MPI_init` is called. Using the CUDA runtime API this can be done with ``` cudaSetDevice(device_no); MPI_init(); ``` However, I don't want to use the call to the CUDA runtime since the rest of my application is purely using the driver API and I'd like to avoid linking also to the runtime. What's wrong in creating the context already before MPI is initialized? In principle nothing. Just wondering if there is an equivalent call in the driver API.