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Bug #854301

AI stops looking too close to its cities when considering want for Migration_Pct effect

Added by Jacob Nevins 6 months ago. Updated 6 months ago.

Status:
Closed
Priority:
Normal
Category:
AI
Target version:
Start date:
Due date:
% Done:

0%

Estimated time:

Description

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.)


Related issues

Related to Freeciv - Bug #854305: mgr_distance setting is misleading about which city it applies toClosed

History

#1 Updated by Marko Lindqvist 6 months ago

By 'inbound migration' you mean that pcity is the migration destination? From mgr_distance documentation ('/explain mgr_distance') it seems that it's source city's radius which counts:
"...for a suitable migration destination when deciding which city to migrate to. The value is added to the current city radius..."

#2 Updated by Jacob Nevins 6 months ago

By 'inbound migration' you mean that pcity is the migration destination?

Yes.

The documentation is a bit misleading -- it is the destination which counts.

I actually ended up down this rabbit hole by following up this complaint about the docs: http://forum.freeciv.org/f/viewtopic.php?f=9&t=91051&p=100459 -- I have a patch in progress for that too.

#3 Updated by Jacob Nevins 6 months ago

  • Related to Bug #854305: mgr_distance setting is misleading about which city it applies to added

#4 Updated by Jacob Nevins 6 months ago

Looking at modpack server, for variant2 this might affect wonder Eiffel Tower (alliance-ranged) as well as Republic/Democracy govs.

#6 Updated by Marko Lindqvist 6 months ago

  • Status changed from Resolved to Closed
  • Assignee set to Marko Lindqvist

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