Freeciv

When considering EFT_MIGRATION_PCT, dai_effect_value() looks for cities near its own which are candidates for inbound migration as follows:

iterate_outward(city_tile(pcity), game.server.mgr_distance + 1, ptile) {
  /* ...look for other players' cities... */
} iterate_outward_end;

However, it should take into account pcity's city radius; see check_city_migrations_player().

I think the only supplied ruleset this affects is 'experimental', which has Migration_Pct effects on governments; the AI will fail to take these into account when thinking about the relative values of governments (dai_gov_value(), adv_best_government()). I don't know exactly what this will affect.

The AI want was added with the Migration_Pct effect in Jul 2009, gna bug #13637, r15795 / commit 734691be95.

mgr_distance was later changed to be relative to the city radius in Mar 2010, gna patch #1232, r17164 / commit f58f12792a; but the AI was not updated.

(I don't have a patch in progress for this ticket; feel free to take it.)