Hi, On 30.06.2014, at 10:00, Tibor Bamhor <tibor...@gmail.com> wrote:
> Well, AI never ever before checked if a bulding listed in productionsites > really exists. There is another part of code (functions lose_building and > gain_buildings) that are called by core and are updating productionsites > list. Widelands has been working this way for years and nobody ever felt a > need to change that (or I as a newcomer do not know about this). the AI was never really ‘working’. It was always very fragile and it contains a bunch of bugs. I do not really understand your resistance - the OPtr code is already implemented and it is very simple to use. If you merge trunk and it still compiles you are golden. > We are talking abut something else, see this line: > > ProductionSiteObserver& site = productionsites.front(); > > Our question is "Is iterator 'site' valid all the time > check_productionsites() function is being executed? The code you posted is always valid in c++ as long as !productionsite.empty(). No change to productionsites can invalidate this code, only a delete &site; will. This never happens until the site is actually destroyed in Widelands. So this is not the bug that valgrind shows you. > I googled quite a lot and it seems there is not a good way to verify validity > of such iterator, only programmer has to be carefull with manipulating > std::list. Manipulation (push_back, pop_back) can make such iterator invalid. There is no iterator in this code. We peek at the content of productionsites() and remove the beginning. No iterator is hold. > Also note that during running AI (DefaultAI::think() and all called > functions) no building is finished or destroyed. AI calls > "send_player_dismantle(*site.site)" and building is dismantled (in fact in > two stages) later, and IA is notified about change via lose_building() and > productionsites list is updated (this is done out of DefaultAI::think() > function). At the end the game is single-threaded, is not it? It is. But the AI in particular is the first thing that would be made multithreaded - the logic never will. But AIs should be able to act in parallel. > Also note that there is update_productionsite_stats() functions that f.e. > queries statistics of buildings in productionsites and if it queried > nonexisting building it would lead to segmentation fault or other problems. > > So brief summary at the end :): > we are talking about different issues: I talk about validity of std:list > iterator, you about possibility that productionsites contains nonexistant > building. Both are realistic issues. I offered a solution for the second problem and I think you should stick with it. Holger > > Regards > > Tibor > > > > 2014-06-30 7:11 GMT+02:00 Holger Rapp <sir...@gmx.de>: >> (should I send the replay to mailing list?) > > yes :). Contacting one dev individually is nearly always the wrong decision. > > Also, you should make a merge request if you want to have your branch > reviewed. And it should be ready for inclusion into trunk from your point of > view, otherwise reviewing is a waste of time. > >> But the summary of situation is here: >> >> My tiborb-ai branch (merged to trunk in revision 6978) contained a bug that >> did not show on linux only on other platforms. >> >> You tried to fix it in revison 6989, but the fix is wrong, valgrind reports >> memory issues and the std::list productionsites is treated incorrectly, >> every time a building is to be checked (all production buildings are checked >> periodically), the buiding is deleted from list and this leads to absurd >> behaviour. AI just doesnt know about own buildings. Visible effect is that >> no mines are built because mines are built only if there are 8 production >> buildings. And AI just believes actual number of buildings is too low >> (decreasing by one by every regular productionsites check - done every +- 20 >> seconds). > > Most buildings should be repushed at the end of the list before returning the > function. But my changes might easily contain errors of course - I find the > AI code hard to understand and there are no tests, so refactorings break > things. Note that no dev has the right to complain about his/her code to be > broken by others if there are no tests :). > >> In tibor-ai2 I added further changes to the AI logic and hopefully fixed the >> crashing. Tested under valgrind, gdb - tenths of hours of gameplay and other >> hundereds without debug tool. But I cannot test it under other platforms. > > While that sounds like a lot of testing, reality shows that just letting the > game run is usually poor testing - it will not test corner cases often > enough. And hundreds of hours is is just 1 hour for a hundred people - i.e. > they will hit corner cases much quicker. Adding tests for your new features > (AND doing the run the game for a while tests) is usually much better. > >> So options are: >> a) we go object pointers way (your design) but somebody (you?) should fix it >> in trunk first, I am not able to >> b) we omit object pointers and stay with old design - this is what is done >> in my branch. > > Why not do both and use object ptrs? They are the correct choice in the sense > of defense programming. I am fine with your changes as long as they do not > crash the game. A bad AI is preferable to a crashing one for sure though. > >> What I suggest: somebody should test under windows/mac and find out it it >> still crashes and if not - I will merge trunk into my branch - option b. >> >> And this is also reason why I did not do any merging of trunk to my branch. >> >> Personally - I spend some time working on this, I feel it is in reasonable >> state and would like to have it merged finally. > > Okay, then propose it for reviewing and request windows and mac feedback. You > will likely not get much until it is merged and hits the nightlies though - > then is when people are really starting to play with it. > > >> >> >> Tibor >> >> >> 2014-06-28 8:12 GMT+02:00 Holger Rapp <sir...@gmx.de>: >> Please merge Trunk Now. Make it a habit to keep your branch up to date with >> trunk by always merging. It will make reviewing easier by making the diff as >> realistic and small as possible. >> >> Also, explaining why trunk ai is broken and how you fixed it will make it >> easier to comment on this part directly. >> >> > Am 27.06.2014 um 23:22 schrieb Tibor Bamhor <tibor...@gmail.com>: >> > >> > Hi all, >> > >> > Please review latest changes I did to AI in branch tibor-ai2 >> > >> > bzr branch lp:~widelands-dev/widelands/tibor-ai2 >> > >> > AI in trunk is still badly broken and I think it is time to fix it. >> > >> > I am interested especially in stability on Windows and Mac platform, as >> > this was a problem with previous iteration of AI. >> > >> > If everything is OK, I will merge trunk there and propose merging into >> > trunk >> > >> > Thanks! >> > >> > Tibor >> > _______________________________________________ >> > Mailing list: https://launchpad.net/~widelands-dev >> > Post to : widelands-dev@lists.launchpad.net >> > Unsubscribe : https://launchpad.net/~widelands-dev >> > More help : https://help.launchpad.net/ListHelp >> > >
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