"the OPtr code is already implemented and it is very simple to use" - well I am not sure about this. Your use of OPtr in AI is broken. Fix it and I will have no problem with this. But I am not that good programmer to figure it out by myself...
front() returns reference, not iterator, you are right, I was wrong. BTW: I today merged trunk and my AI, but without object pointer, now I am testing it... Tibor 2014-07-01 6:23 GMT+02:00 Holger Rapp <[email protected]>: > Hi, > On 30.06.2014, at 10:00, Tibor Bamhor <[email protected]> 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 <[email protected]>: > >> (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 <[email protected]>: >> >>> 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 <[email protected]>: >>> > >>> > 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 : [email protected] >>> > Unsubscribe : https://launchpad.net/~widelands-dev >>> > More help : https://help.launchpad.net/ListHelp >>> >> >> >> > >
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