Question

I have a program in C++ that is designed to run a simulation for a summer project I’m doing. It is pretty computationally intensive, but I have gotten permission to use a cluster computer’s resources to run it, but I test it and develop it on my own laptop. This program generates text files as output, and this is where I run into trouble.

I need the text files to be saved in different paths depending on whether I’m running the program on my own computer or on the cluster computer. My solution for now has been to use $(shell hostname) in my makefile to check which machine the code is being compiled on and, from that output, use conditional compilation with macros defined from that operation in the makefile. At one time, I was using two different versions of a header that defined macros differently on my computer versus the cluster, but I’m using a git repository to transfer changes back and forth, and I was having a very difficult time excluding one file like this.

I was just wondering what is the most preferable practice to set paths at compile time on different computers with the same source.

Answer 1

It doesn’t sound to me like it needs to compile differently on different machines. It sounds like it needs to take some paths at run-time from either the command line, or from some sort of config file.

One suggestion would be to use the boost program options library which in one simple setup allows you to read the same params either from the command line or from a config file. This is what I used when running similar jobs on a big cluster or on my laptop and it worked nicely.

Below is a simple example from their docs:

// Declare the supported options.
po::options_description desc("Allowed options");
desc.add_options()
    ("help", "produce help message")
    ("compression", po::value<int>(), "set compression level")
;

po::variables_map vm;
po::store(po::parse_command_line(ac, av, desc), vm);
po::notify(vm);    

if (vm.count("help")) {
    cout << desc << "\n";
    return 1;
}

if (vm.count("compression")) {
    cout << "Compression level was set to " 
 << vm["compression"].as<int>() << ".\n";
} else {
    cout << "Compression level was not set.\n";
}