Perform only spatial prolongation when using a single timelevel and tag 'prolongation="copy"'

[Miguel Zilhão]

Sometimes it is useful to set a grid function that does not evolve at all. However, using a single timelevel and tag 'prolongation="copy"' results in a Carpet assertion failure.

This is fixed in the following commit d13a6e245a3d7d2b575094fd0def540d510a166c, as discussed in the following thread: http://lists.einsteintoolkit.org/pipermail/users/2017-October/005835.html

Could this be merged to master?

Keyword:

[Erik Schnetter]

We can introduce a new prolongation operator and/or introduce a way to set the desired time prolongation order per grid function group.

[Roland Haas]

This seems to be correct to apply. op_copy appears in data<T>::transfer_prolongate like so:

  switch (transport_operator) {

  case op_copy:
  case op_Lagrange: {
    static HighResTimer::HighResTimer timer("prolongate_Lagrange");
    auto timer_clock = timer.start();
    // enum centering { vertex_centered, cell_centered };
    switch (cent) {
    case vertex_centered: {
      static void (*the_operators[])(
          T const *restrict const src, ivect3 const &restrict srcpadext,
          ivect3 const &restrict srcext, T *restrict const dst,
          ivect3 const &restrict dstpadext, ivect3 const &restrict dstext,
          ibbox3 const &restrict srcbbox, ibbox3 const &restrict dstbbox,
          ibbox3 const &restrict srcregbbox, ibbox3 const &restrict dstregbbox,
          void *const extraargs) = {
          NULL, &prolongate_3d_rf2<T, 1>, NULL, &prolongate_3d_rf2<T, 3>,
          NULL, &prolongate_3d_rf2<T, 5>, NULL, &prolongate_3d_rf2<T, 7>,
          NULL, &prolongate_3d_rf2<T, 9>, NULL, &prolongate_3d_rf2<T, 11>,
      };

i.e. it interpolates in space the same way the op_Lagrange does. It also appears in GroupStorageCheck like so

    if (op != op_none and op != op_sync and op != op_restrict and
        op != op_copy) {
      int const tls = groupdata.AT(group).activetimelevels.AT(ml).AT(rl);
      if (tls != 0 and tls < prolongation_order_time + 1) {
        static vector<bool> didwarn;
        didwarn.resize(CCTK_NumGroups(), false);
        if (not didwarn.AT(group)) {
          // Warn only once per group
          didwarn.AT(group) = true;
          char *const groupname = CCTK_GroupName(group);
          CCTK_VInfo(CCTK_THORNSTRING,
                     "There are not enough time levels for the desired "
                     "temporal prolongation order in the grid function group "
                     "\"%s\".  With Carpet::prolongation_order_time=%d, you "
                     "need at least %d time levels.",
                     groupname, (int)prolongation_order_time,
                     (int)(prolongation_order_time + 1));
          free(groupname);
        }

i.e. it does need only a single timelevel.

No thorn in the toolkit currently uses op_copy so the change would be harmless.

[Roland Haas]

Please review.

[Roland Haas]

Already positively reviewed in https://bitbucket.org/einsteintoolkit/tickets/issues/2086/perform-only-spatial-prolongation-when#comment-54832209 .
Unless objected I will apply this after 2020-05-31.

[Roland Haas]

Applied as git hash e562bfcc "CarpetLib: Use original spatial prolongation order for op_copy" of carpet