Does CUDA applications' compute capability automatically upgrade?

Question

If I compile a CUDA program with a lower Compute Capability, e.g 1.3 (nvcc flag sm_13), and run it on a device with Compute Capability 2.1, will it exploit the features of Compute 2.1 or not?

In that situation, Will the compute 2.1 device behave like a compute 1.3 device?

Answer 1

No, it won't exploit any features you need to explicitly program for. Only those features that are transparent to the user (like cache or larger register files) will be used.

Additionally, you need to make sure your object file contains a version of the code compiled to the PTX intermediate language, that can be dynamically compiled to the target architecture, or you program will not even run.

Compile to a virtual architecture (nvcc -arch compute_13) to ensure that, or create a fat binary with code for multiple architectures using the -gencode option to nvcc.

With a fat binary, you can program for features available only on higher compute capability if you wrap the code inside #if __CUDA_ARCH__ >= xyz preprocessor conditionals.