immediate_receive and count? about rsmpi HOT 1 OPEN

That seems like it could be a good idea. Something like immediate_receive(count)?

There's also the immediate_receive_into_*() set of functions, which would allow you to do an MPI_IRecv with a count. These take a mutable reference to some buffer of a fixed size and then return a request. To ensure that this buffer isn't dropped while MPI is still using it, you have to wrap your code in a closure that takes a Scope object and ensure that you allocate any buffers outside the closure. Before exiting the closure, all requests must be waited on, or else it will panic.

examples/immediate.rs is a good example that demonstrates this.

For the current version of immediate_receive(), I think you might be able to work around this if you derived Equivalence on a struct containing a buffer. Something like this:

#[derive(Equivalence)]
struct Wrapper {
    buf: [u8; 128],
}

Then you should be able to do an immediate_receive::<Wrapper>() to pass around a buffer. The count will then be fixed at compile time, however.

from rsmpi.