Client-Server Communication via Shared Memory

UM-Bridge uses HTTP to communicate between an UQ client and a model server by default. However, this is not the most performant option (in HPC) as it carries around 1 millisecond of overhead per request. We provide a quicker alternative that uses shared memory (RAM) to transfer data. This approach works by using allocated memory buffers in RAM as the transfer medium for UM-Bridge inputs and outputs. To prevent data races in a parallel setting, each memory buffer is tagged with the ID of the thread making the request in the parallel client, and this ID is shared through a JSON entry so that the model can access the correct buffer.

Currently, only the C++ and Python implementations are supported, and this feature is off by default unless enabled through the use_shmem option when instantiating the HTTPModel object. The code will first perform a test transfer using shared memory to check whether the client and server are able to communicate; it reverts back to HTTP if this test fails.