C++ Programming :: Can there be problems when a class is multiply inherited from 1000s of classes


	Can there be problems when a class is multiply inherited from 1000s of classes Hi All, We have done a object oriented design for a system which will create a class multiply inherited by around 1000 small and medium sized classes. I would be greatful if you can help me with the following: Can this create any problems with GNU g++ compilation, linking etc? What would be the impact to the performance of the system? Anything else we have to consider? Thanks Janaka Janaka Perera wrote: > Hi All, > We have done a object oriented design for a system which will create a > class multiply inherited by around 1000 small and medium sized > classes. > I would be greatful if you can help me with the following: > Can this create any problems with GNU g++ compilation, linking etc? > What would be the impact to the performance of the system? > Anything else we have to consider? > Thanks > Janaka 'class is multiply inherited from 1000s of classes' 'class multiply inherited by around 1000 small and medium sized classes' Which one do you mean? It makes quite a big difference. john Sorry.. it should be around 1000 classes, not 1000s On 28 Maj, 11:06, Janaka Perera <janaka@gmail.com> wrote: >>> Janaka Perera wrote: >>> We have done a object oriented design for a system which will create a >>> class multiply inherited by around 1000 small and medium sized >>> classes. >>> I would be greatful if you can help me with the following: >>> Can this create any problems with GNU g++ compilation, linking etc? >>> What would be the impact to the performance of the system? >>> Anything else we have to consider? >>'class is multiply inherited from 1000s of classes' >>'class multiply inherited by around 1000 small and medium sized classes' >>Which one do you mean? It makes quite a big difference. > Sorry.. it should be around 1000 classes, not 1000s First of all, please quote the text you are replying to (fixed above). What John asked was if the object you are talking about will inherit from 1000 classes or if 1000 different classes will inherit from the object. In the later case there should be no problems. In the first case there might be some problems with the compiler (though I doubt it) and there might be an impact on performance. However that would probably be the least of your problem since trying to maintain such a monster would be a nightmare. -- Erik Wikstrm On 28 May, 10:06, Janaka Perera <janaka@gmail.com> wrote: > Sorry.. it should be around 1000 classes, not 1000s What should be 1000 not 1000s? You didn't quote any context and your message makes no sense on its own. Please see http://cfaj.freeshell.org/google/ Thanks. Context added back in - but look how much manual cutting and pasting I've had to do to put the context back in. Don't expect me (or, I imagine, most other people) to do that for you very often. [Janaka Perera] [Subject: Can there be problems when a class is multiply inherited from 1000s of classes] We have done a object oriented design for a system which will create a class multiply inherited by around 1000 small and medium sized classes. I would be greatful if you can help me with the following: Can this create any problems with GNU g++ compilation, linking etc? What would be the impact to the performance of the system? Anything else we have to consider? [John Harrison] 'class is multiply inherited from 1000s of classes' 'class multiply inherited by around 1000 small and medium sized classes' Which one do you mean? It makes quite a big difference. [Janaka Perera] Sorry.. it should be around 1000 classes, not 1000s [Me] I don't think John Harrison is worried about the difference between the number of classes being 1000 or 1000s. The distinction between one thousand and many thousands is unlikely to be significant. One thousand may well be quite enough to introduce problems if there are going to be any. The important distinction is (my emphasis): 'class is multiply inherited FROM 1000s of classes' 'class multiply inherited BY around 1000 small and medium sized classes' Which is it? Gavin Deane On May 28, 9:47 am, Janaka Perera <janaka@gmail.com> wrote: > Hi All, > We have done a object oriented design for a system which will create a > class multiply inherited by around 1000 small and medium sized > classes. > I would be greatful if you can help me with the following: > Can this create any problems with GNU g++ compilation, linking etc? > What would be the impact to the performance of the system? > Anything else we have to consider? > Thanks > Janaka Although there are some cases, when its intended, both might be a sign of novice design/design misuse. None of those should pose any significant compilation problems under gnu. But, the class inheriting from 1k others will compile slowly, very slowly imho. regards, pawel On May 28, 2:40 pm, Gavin Deane <deane_ga@hotmail.com> wrote: - Hide quoted text - > On 28 May, 10:06, Janaka Perera <janaka@gmail.com> wrote: > > Sorry.. it should be around 1000 classes, not 1000s > What should be 1000 not 1000s? You didn't quote any context and your > message makes no sense on its own. Please see > http://cfaj.freeshell.org/google/ > Thanks. Context added back in - but look how much manual cutting and > pasting I've had to do to put the context back in. Don't expect me > (or, I imagine, most other people) to do that for you very often. > [Janaka Perera] > [Subject: Can there be problems when a class is multiply inherited > from 1000s of classes] > We have done a object oriented design for a system which will create a > class multiply inherited by around 1000 small and medium sized > classes. > I would be greatful if you can help me with the following: > Can this create any problems with GNU g++ compilation, linking etc? > What would be the impact to the performance of the system? > Anything else we have to consider? > [John Harrison] > 'class is multiply inherited from 1000s of classes' > 'class multiply inherited by around 1000 small and medium sized > classes' > Which one do you mean? It makes quite a big difference. > [Janaka Perera] > Sorry.. it should be around 1000 classes, not 1000s > [Me] > I don't think John Harrison is worried about the difference between > the number of classes being 1000 or 1000s. The distinction between one > thousand and many thousands is unlikely to be significant. One > thousand may well be quite enough to introduce problems if there are > going to be any. The important distinction is (my emphasis): > 'class is multiply inherited FROM 1000s of classes' > 'class multiply inherited BY around 1000 small and medium sized > classes' > Which is it? > Gavin Deane It's FROM 1000s of classes.. Sorry for the inconvenience caused. I am new to this posting thing. Actually this is my first post. Thanks a lot for the instructions. I'll refer http://cfaj.freeshell.org/google/ On May 28, 2:31 pm, Erik Wikstrm <eri@student.chalmers.se wrote: On 28 Maj, 11:06, Janaka Perera <janaka@gmail.com wrote: [Janaka Perera] We have done a object oriented design for a system which will create a class multiply inherited by around 1000 small and medium sized classes.<snip> [Erik Wikstrm] What John asked was if the object you are talking about will inherit from 1000 classes or if 1000 different classes will inherit from the object. In the later case there should be no problems. In the first case there might be some problems with the compiler (though I doubt it) and there might be an impact on performance. However that would probably be the least of your problem since trying to maintain such a monster would be a nightmare. [Me] It's the first case. If there is a performance impact, it definitely going to be a problem for us. But maintaining the code will not be a much problem since we are developing a code generator which will generate code using a meta-base. Thanks Janaka - Hide quoted text - Janaka Perera wrote: > On May 28, 2:40 pm, Gavin Deane <deane_ga@hotmail.com> wrote: >> On 28 May, 10:06, Janaka Perera <janaka@gmail.com> wrote: >>> Sorry.. it should be around 1000 classes, not 1000s >> What should be 1000 not 1000s? You didn't quote any context and your >> message makes no sense on its own. Please see >> http://cfaj.freeshell.org/google/ >> Thanks. Context added back in - but look how much manual cutting and >> pasting I've had to do to put the context back in. Don't expect me >> (or, I imagine, most other people) to do that for you very often. >> [Janaka Perera] >> [Subject: Can there be problems when a class is multiply inherited >> from 1000s of classes] >> We have done a object oriented design for a system which will create a >> class multiply inherited by around 1000 small and medium sized >> classes. >> I would be greatful if you can help me with the following: >> Can this create any problems with GNU g++ compilation, linking etc? >> What would be the impact to the performance of the system? >> Anything else we have to consider? >> [John Harrison] >> 'class is multiply inherited from 1000s of classes' >> 'class multiply inherited by around 1000 small and medium sized >> classes' >> Which one do you mean? It makes quite a big difference. >> [Janaka Perera] >> Sorry.. it should be around 1000 classes, not 1000s >> [Me] >> I don't think John Harrison is worried about the difference between >> the number of classes being 1000 or 1000s. The distinction between one >> thousand and many thousands is unlikely to be significant. One >> thousand may well be quite enough to introduce problems if there are >> going to be any. The important distinction is (my emphasis): >> 'class is multiply inherited FROM 1000s of classes' >> 'class multiply inherited BY around 1000 small and medium sized >> classes' >> Which is it? >> Gavin Deane > It's FROM 1000s of classes.. > Sorry for the inconvenience caused. I am new to this posting thing. > Actually this is my first post. Thanks a lot for the instructions. > I'll refer http://cfaj.freeshell.org/google/ Right, that is a strange design. I have no experience with similar designs, nor I suspect do many people. I think you are just going to have to try it and find out. Is this some kind of template meta-programming exercise? If find it hard to believe that you've written class Strange : public <huge list of 1000 classes here> { }; but with TMP you could achieve something similar. My guess would be that you can expect problems, as you should examine carefully the benefits of such a design. But as I said I have no experience. john On 28 Maj, 13:05, Janaka Perera <janaka@gmail.com> wrote: - Hide quoted text - > On May 28, 2:31 pm, Erik Wikstrm <eri@student.chalmers.se wrote: > On 28 Maj, 11:06, Janaka Perera <janaka@gmail.com wrote: > [Janaka Perera] > We have done a object oriented design for a system which will create a > class multiply inherited by around 1000 small and medium sized > classes.<snip> > [Erik Wikstrm] > What John asked was if the object you are talking about will inherit > from 1000 classes or if 1000 different classes will inherit from the > object. > In the later case there should be no problems. In the first case there > might be some problems with the compiler (though I doubt it) and there > might be an impact on performance. However that would probably be the > least of your problem since trying to maintain such a monster would be > a nightmare. > [Me] > It's the first case. If there is a performance impact, it definitely > going to be a problem for us. But maintaining the code will not be a > much problem since we are developing a code generator which will > generate code using a meta-base. If one might ask, how did you come up with that design. I can't think of any good reason to inherit from so many classes. You can't possibly have that many interfaces so you are most probably inheriting to get functionality, but if you use generation why not just put it straight in the class? -- Erik Wikstrm On May 28, 4:57 pm, Erik Wikstrm <eri@student.chalmers.se> wrote: - Hide quoted text - > On 28 Maj, 13:05, Janaka Perera <janaka@gmail.com> wrote: > > On May 28, 2:31 pm, Erik Wikstrm <eri@student.chalmers.se wrote: > > On 28 Maj, 11:06, Janaka Perera <janaka@gmail.com wrote: > > [Janaka Perera] > > We have done a object oriented design for a system which will create a > > class multiply inherited by around 1000 small and medium sized > > classes.<snip> > > [Erik Wikstrm] > > What John asked was if the object you are talking about will inherit > > from 1000 classes or if 1000 different classes will inherit from the > > object. > > In the later case there should be no problems. In the first case there > > might be some problems with the compiler (though I doubt it) and there > > might be an impact on performance. However that would probably be the > > least of your problem since trying to maintain such a monster would be > > a nightmare. > > [Me] > > It's the first case. If there is a performance impact, it definitely > > going to be a problem for us. But maintaining the code will not be a > > much problem since we are developing a code generator which will > > generate code using a meta-base. > If one might ask, how did you come up with that design. I can't think > of any good reason to inherit from so many classes. You can't possibly > have that many interfaces so you are most probably inheriting to get > functionality, but if you use generation why not just put it straight > in the class? > -- > Erik Wikstrm To make it better understandable, we are talking about a shared library in Solaris platform generated by a code generator using Meta - information. The reasons behind the design are 1. We can't generate the whole code set in to a single file because GNU g++ cannot compile it even using a server with 16GB RAM in it for the reason that code is too large. 2. We have a set of common functions in the API which every program uses this library wants. There are also another set of functionalities requires by other modules (executables/libraries) depending its requirement (lets say classes that represents entities). Some classes are shared by multiple modules. By using this design we can inherit the classes that we want and create similar interfaces(header files) for each module which uses the API and still use the same shared library since the symbols are same( We need all the interfaces inherited only for a one module which uses this module) 3. If we include the whole header information in to a single file without separating and including only necessary ones, compilation of the modules which uses this API take hours to compile.(true, it will take a lot of time for this module to compile but it's a one time compilation) On May 28, 11:47 am, Janaka Perera <janaka@gmail.com> wrote: > Hi All, > We have done a object oriented design for a system which will create a > class multiply inherited by around 1000 small and medium sized > classes. > I would be greatful if you can help me with the following: > Can this create any problems with GNU g++ compilation, linking etc? > What would be the impact to the performance of the system? > Anything else we have to consider? > Thanks > Janaka Depends on "how does it multiply inherited"(there is virtual inheritance, for example) and "what is classes it multiply inherited form"(have they base classes too? have they vtable(any virtual functions, declared in those or those bases)?) and some other things... On May 28, 2:02 pm, Janaka Perera <janaka@gmail.com> wrote: - Hide quoted text - > On May 28, 4:57 pm, Erik Wikstrm <eri@student.chalmers.se> wrote: > > On 28 Maj, 13:05, Janaka Perera <janaka@gmail.com> wrote: > > > On May 28, 2:31 pm, Erik Wikstrm <eri@student.chalmers.se wrote: > > > On 28 Maj, 11:06, Janaka Perera <janaka@gmail.com wrote: > > > [Janaka Perera] > > > We have done a object oriented design for a system which will create a > > > class multiply inherited by around 1000 small and medium sized > > > classes.<snip> > > > [Erik Wikstrm] > > > What John asked was if the object you are talking about will inherit > > > from 1000 classes or if 1000 different classes will inherit from the > > > object. > > > In the later case there should be no problems. In the first case there > > > might be some problems with the compiler (though I doubt it) and there > > > might be an impact on performance. However that would probably be the > > > least of your problem since trying to maintain such a monster would be > > > a nightmare. > > > [Me] > > > It's the first case. If there is a performance impact, it definitely > > > going to be a problem for us. But maintaining the code will not be a > > > much problem since we are developing a code generator which will > > > generate code using a meta-base. > > If one might ask, how did you come up with that design. I can't think > > of any good reason to inherit from so many classes. You can't possibly > > have that many interfaces so you are most probably inheriting to get > > functionality, but if you use generation why not just put it straight > > in the class? > > -- > > Erik Wikstrm > To make it better understandable, we are talking about a shared > library in Solaris platform generated by a code generator using Meta - > information. > The reasons behind the design are > 1. We can't generate the whole code set in to a single file because > GNU g++ cannot compile it even using a server with 16GB RAM in it for > the reason that code is too large. > 2. We have a set of common functions in the API which every program > uses this library wants. There are also another set of functionalities > requires by other modules (executables/libraries) depending its > requirement (lets say classes that represents entities). Some classes > are shared by multiple modules. By using this design we can inherit > the classes that we want and create similar interfaces(header files) > for each module which uses the API and still use the same shared > library since the symbols are same( We need all the interfaces > inherited only for a one module which uses this module) > 3. If we include the whole header information in to a single file > without separating and including only necessary ones, compilation of > the modules which uses this API take hours to compile.(true, it will > take a lot of time for this module to compile but it's a one time > compilation) I did a POC, created a class multiply inherited from 1500 classes. Everything is successfully working without a problem. Wanted let you all know. Thanks for all who replied.