In my field (analog hardware for deep learning) "in situ" (e.g. in situ training) means operations are executed in hardware, while "ex-situ" means a simulation

In my field (analog hardware for deep learning) "in situ" (e.g. in situ training) means operations are executed in hardware, while "ex-situ" means a simulation of the hardware running the model is done in software (on CPU/GPU).