Matias Capeletto said: (by the date of Tue, 17 Jul 2007 14:28:28 -0300)
It was accepted in march :) But your feedback will be great! Really...
Hi Matias, thanks for your faith in... how good my comments might be :) Currently I'm not going to go straight to the C++ coding (aka. testing Bimap "live"). I am preparing grounds for huge refactoring. And I'm looking at how to do it the best way. My codebase of 15k lines already works quite good. Now in fact I want to reorganize everything inside so it will be clean again. Because currently more and more hacks appear to get something done. I plan to stop using my own plugin-loading and serialization library and switch to boost::extension and ::serialization. Propose my own Multimethods lirbary for boost inclusion (after boostifying it ;). And stop using my own containers, but use boost instead. So... in fact I have another question about containers. But I'm afraid that bimap is not an answer here... So I keep [multi_index] in the subject line :-) Imagine that in my scientific simulation software I have bodies that can interact with each other. Any number of bodies can interact. As you already know, bodies are idenfied by id numbers. But interactions are identified by std::set<int> - a group of bodies that are interacting. So I have a class Interaction and it's indexed by sets of numbers like: identifier interaction 1,2,3 class Interaction between boedies 1,2,3 2,3 Interaction 3,4 Interaction 2,4,6 some other Interaction This is 'groups' in fact (the one with which I started this thread). To make stuff easier to manage, I'll use negative numbers for group_id and positive for body_id. So basically I could rewrite above with: identifier interaction -1 class Interaction between boedies 1,2,3 -2 Interaction -3 Interaction -4 some other Interaction What I need here is a *cooperation* between containers (because information about group components is stored in other container). So with the Interaction container above I need to iterate FAST on following things: - all interactions from first to last (easy) - all bodies that take part in interaction -3, answer is: 3,4 - all interactions in which body 3 is involved, answer is: -1,-2,-3 This is convoluted :) And even worse... becasue I need interactions to have groups too! We can call it a group of groups, like this: identifier group interaction -1 -5 class Interaction between boedies 1,2,3 -2 -5 Interaction -3 -6 Interaction -4 -6 some other Interaction You can see that group -5 has two components: -1,-2, and group -6 has -3 and -4. now I need to - iterate over all interactions from group -5, answer is: -1 -2 - iterate over all bodies from group -5, answer is: 1,2,3 - all interactions involving body 3 that are in group -5, answer: -1 -2 - all interactions in which group of bodies 2 and 3 interact, answer: -1 -2 (may be slower) I'm stil not sure if that's all i need. Still working on it ;-) The hardest(??) part is that I will need separate containers (cannot make one huge container for everything). So imagine, I have a class Model, that holds the context of my computations. To simplify a little: I have two classes that describe a single body. Those are BodyState (position, velocity) and BodyShape (vertex positions). They reside in a std::map. So, I say, that body_states[5] and body_shapes[5] describe the same body with body_id=5. And If I need to know to which groups it belongs I look in groups[5]. To see its name (a body could have name too) I see into names[5]. Like this: typedef int id; typedef id body_id; typedef id group_id; class Model { bimap< tagged< int, body_id >, multiset_of< tagged< int, group_id > > > groups; // a bimap between positive body_id <-> negative group_id bimap<id,std::string> names; std::map<body_id , BodyState*> body_states; std::map<body_id , BodyShape*> body_shapes; /* Now I want to throw interactions into the basket. They can (I'm still not sure) use the 'groups' container to index the content. Easiest is to say: */ std::map<group_id, Interaction*> interactions; }; But here, group_id used in 'interactions' is a "group of groups". And (of course) I want to iterate over all interactions involved (or bodies involved) as described above. So I guess that I need multi_index here, since bimap won't be enough? :) PS: actually I have more classes and containers here, this is simplified a bit. This is not the end.... ;) But for the next part I'm almost sure that I'll need a custom container. I'll not describe it now, just to keep you excited a bit. -- Janek Kozicki |