sandbox/Antoonvh/mwe_vtp.c

    A minimal example for a crashing call to the reposition() function.

    Thanks to Omri Argov for discovering this flaw.

    We take some setup inspiration from this test.

    Plot the last known locations:

    set size ratio -1
set key right outside
plot 'out' w l t 'Cells', 'last_known' , #\
   #   'last_facets' w l lw 3
    This is the intended result (script)

    The crash can be reproduced by reverting this patch:

    https://basilisk.fr/sandbox/Antoonvh/vof-tracer-particles.h?changes=20200421105835

    You will find that it corresponds to particles moving out the domain.

    Setup

    Omri correctly expected that the issue arises when particles move out the domain. We set that up, and output some data for visualization.

    #include "vof-tracer-particles.h" //We need the reposition function
#include "vof.h"                  //Which expects a vof field f.

Particles Pin;
double R = 0.2, yo = 0.5, xo = 0.5;
#define circle(x,y) (sq(R) - (sq(x - xo) + sq(y - yo)))

face vector uf[];

scalar f[], * interfaces = {f};

int main() {
  N = 32;
    implicit declaration of function ‘run’ [-Werror=implicit-function-declaration] 
      run();
}

event init (t = 0) {
  fraction (f, circle (x, y));
  Pin = new_vof_tracer_particles (10,1);
    variable ‘I’ has initializer but incomplete type
    storage size of ‘I’ isn’t known 
      struct Init_P I = {10, xo, yo, R};
  place_in_circle (Pin, I);
  foreach_face(x)
    uf.x[] = 1;
  output_cells();
}

event set_dtmax (i++)
  dt = dtnext (0.005);

event trace_pos (i++) {
  FILE * fp = fopen ("last_known", "w"); 
  foreach_particle()
    fprintf (fp, "%g %g\n", x, y);
  fclose (fp);
  
  FILE * fpf = fopen ("last_fac", "w");
  output_facets (f, fp = fpf);
  fclose (fpf);
  }

event stop (t = 0.75);