Giters

rabauke / mpl

A C++17 message passing library based on MPI

Home Page:https://rabauke.github.io/mpl/html/

Geek Repo:Geek Repo

Github PK Tool:Github PK Tool

const problems with native handle

VictorEijkhout opened this issue · comments

commented 
    const mpl::communicator &comm =
      mpl::environment::comm_world();
    MPI_Comm
      world_extract = comm.native_handle(),

gives error: 'this' argument to member function 'native_handle' has type 'const mpl::communicator', but function is not marked const

but without const

    mpl::communicator &comm =
      mpl::environment::comm_world();

gives error: binding reference of type 'mpl::communicator' to value of type 'const mpl::communicator' drops 'const' qualifier

commented

You could fix this by making native_handle a const function, but I gues the point to having the native handle is to do MPI_Comm_set_info and such on it.

commented

@VictorEijkhout: I was expecting this. You can replace mpl::environment::comm_world() just by MPI_COMM_WORLD. Thus, this is not an issue.

Nevertheless, I will need to make the native_handle method const (not its return value). The reason is, that communicators should be passed as constant references to functions. (MPL communicators have a value semantics. Copying a communicator involves MPI_Comm_dup, which is usually undesirable.) Thus, if the underling MPI handle of the function argument is needed then we run into the same problem as above with mpl::environment::comm_world().

commented
commented