[Freeciv-Dev] (PR#12682) AI Ignores Building Effects for Tech. Wants

["Benedict Adamson" <badamson@xxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=12682 >

After examining the AI city improvement code, I can not find anywhere 
that the AI increases its want (pplayer->ai.tech_want[t]) for a 
technology because that technology allows improvements that have a 
particular desirable effect.

There is analogous code for increasing the desire for a technology 
because it allows useful military units (in process_defender_want and 
process_attacker_want), caravans (in ai_choose_help_wonder), diplomats 
(in ai_choose_diplomat_defensive), governments (in 
ai_manage_government), ferries for colonisation 
(find_best_city_placement) and units in general (ai_wants_role_unit). 
Have I missed something?

If a city desires a (future) improvement that has a particular effect, 
the AI should increase its desire for the technology (or technologies) 
that allow building that improvement.

I believe this is a problem based on observation of the updated 
'ancients' mod-pack, which I am working on. The AI does not build 
Temples, and consequently its cities often have excessive Elvi and fall 
into disorder. The technology tree for this mod-pack is different from 
default. In it, the technology to build Temples, Polytheism, is not on 
the path for producing any low-technology units or governments (contrast 
with Ceremonial Burial in the default ruleset, which is necessary for 
Monarchy and thus indriectly for Pikemen and Knights). What is more, for 
the ancients mod-pack, the  technology that depends on Polytheism and 
that allows production of some military units, Dark Age, renders Temples 
obsolete, so by the time the AI bothers to research Polytheism, it soon 
after becomes unable to build Temples.