possible misuse of std::string in the MPI_Bcast call in Broadcast.cpp.

[grnydawn]

From reviewing the Omega source code, I noticed warnings about the misuse of std::string in the MPI_Bcast call in Broadcast.cpp. I am not 100% sure whether this is a real issue, but I thought it was worth bringing up here.

Currently, the Broadcast function for the std::string type contains the following line:

MPI_Bcast((void *)Value.c_str(), Value.size(), MPI_CHAR, Root, Comm);

I was advised to replace it with:

MPI_Bcast(&Value[0], Value.size(), MPI_CHAR, Root, Comm);

to prevent the potential issue that Value.c_str() returns a const char*.

[philipwjones]

@grnydawn I suspect it's not an issue. MPI needs the pointer to the underlying char array. I've used the &Vector[0] paradigm elsewhere in the infrastructure, so it should be fine if we want to remove the warning. I'll create a PR unless @amametjanov beats me to it.

[grnydawn]

Thanks, @philipwjones, for the comment. It would be great if you could create a PR for this. Alternatively, I am preparing another PR based on some findings from a recent large-scale Omega run, so I can include this change in that PR as well.

[philipwjones]

@grnydawn Sure, go ahead and make the change in your PR.