• Matthieu Schaller's avatar
    Merge branch 'kill_drift' into 'master' · 49e93734
    Matthieu Schaller authored
    Only drift the particles that need drifting
    
    Here is an algorithmic speed-up. The plan is to drift only the cells that contain an active particles and the cells that have at least one neighbour with an active particle. 
    
     - If this condition is not met then `runner_do_drift()` just returns without performing any operation. 
    
     - If the condition is met, `runner_do_drift()` moves all particles (as before) from the last point in time where a drift was performed. 
    
    We record for each cell the last time a drift was done such that we now by how much to drift things when needed.
    
    Two exceptions to this rule: before reconstructing and before duping a snapshot,  we drift all particles as we need correct position information at these two stages.
    
    Note that I have made this an engine policy to ease the testing. Drifting all particles can be restored by setting the right flag.
    
    @nnrw56  could you check that the function `cell_is_drift_needed()` makes sense and fully does what it says it does ? Also could you let me know whether you also agree with the whole logic and implementation.
    
    
    See merge request !225
    49e93734