PID file

[Artoria2e5]

A PID file for multi-launch detection/prevention might be helpful. Multi-launch on the same worktodo file wastes energy and... energy, I guess.

Specific use case: this would simplify pause-restart scripts. If multi-launch is prevented, a script can just always call start.

Implementation suggestion: extend the existing file-lock system, just make a mfakto.lck.

[Artoria2e5]

Draft commit pushed in my branch but it does not work remove the file if interrupted during compilation. I should perhaps test if it works during normal operation.

[tdulcet]

Implementation suggestion: extend the existing file-lock system, just make a mfakto.lck.

PIDs can be reused by the OS, so using a PID file would be unreliable. Using a .lck file would mean that users would be unable to restart mfakto after a crash or hard shutdown, without manually deleting the file. You may want to look into what I suggested here, so that the locks could be automatically cleaned up by the OS.

[ixfd64]

Another potential issue is that multiple instances are needed to fully utilize a GPU when sieving on the CPU. However, this is probably an uncommon use case because most people sieve on the GPU nowadays.