Le 28/12/2012 19:11, Phil Steitz a écrit : > On 12/28/12 9:58 AM, Luc Maisonobe wrote: >> Le 28/12/2012 17:51, Konstantin Berlin a écrit : >>> Hi, >>> >>> I can understand Dimitri's frustration, it seems the optimization >>> framework gets worse with every iteration. However, we should >>> probably look forward and think about how to design it properly >>> instead. >>> >>> Several times I brought out some problems and ideas about the package >>> and it seems the only person who has an opinion is Gilles. >> Several people contributed to the thread (see >> <http://commons.markmail.org/thread/i6klmc2ytflb6qnt>), but as Gilles >> pointed out in one of the message, we lack an optimization expert. I >> sincerely would not want my opinion to be taken too seriously on this, >> so I only expressed what I could and did not decide anything by myself >> (only proposed to remove the wrong binding with DerivativeStructure, >> which has since been done). >> >>> I will list what I consider to be major problems >>> 1) The OO design is bad, too much inheritance which could be handled >>> better by interfaces, the structure has no relation to the actual way >>> parts of optimizers can be mixed and matched. Input functions should >>> also have clear inheritance structure and should return both the >>> value, gradient, hessian in one function call. >> I strongly agree with Konstantin here. Abstract classes allow to add >> methods without breaking compatibility (which is good), but they also >> have some drawbacks (we have seen one drawback with the parameterized >> classes a few months ago, and this huge hierarchy is another one). So >> there is no silver bullet and we keep trying to find the good balance. >> As far as I am concerned, I would prefer we get fewer abstract classes, >> we remove some intermediate level (I don't know which ones), and we use >> more delegation than inheritance. >> >>> 2) Incorrect handling of constraints. There are only something like 5 >>> possible constraints possible in optimization, with each >>> implementation of the solver handling some but not all. There is no >>> need to this runtime approach, which creates incredible amount of >>> confusion. All the possible constraints should be explicitly given in >>> the parameters to a function call, there are only 5. In addition, >>> constraints should be pre-processed a priori! So they should be an >>> input to the constructor not to the optimization function call. >> Our implementation for constraints is really limited (once again, scarce >> resources). What are the 5 types you consider? Simple/double bounds on >> parameters, linear/non-linear bounds and equality? >> >>> 3) Linear algebra package should be used as an interface and >>> internally to increase performance for larger datasets. Data copying >>> should be avoided as much as possible. >> Yes, but this would require solving another sub-problem first: having a >> decent sparse linear algebra implementation, which we also lack. Our >> implementation for full matrices was also in a sorry state prior to 3.0, >> but now fortunately this has improved at least for systems up to a few >> thousands rows and columns (so at least we do make progress on some points). >> >>> 4) Testing should be done on larger problems. >> Yes. I guess there are some general well known problems for that, so we >> should get a few of them and implement them. We did implement a number >> of tests from Minpack, but they focused on difficult cases rather than >> on problem size. I think optimization has a good testing coverage, but >> clearly large size problems is a needed addition. >> >>> I know the response is that I am free to go implemented, but I think >>> we should at least agree on design principles instead of pushing >>> through your own ideas because the other person is too busy. The only >>> discussion we ever had on this was between me and Gilles, everyone >>> else disappeared. >> Well, we tried to keep up as our skills allowed, and we were also >> concerned with 3.1 being released at the same time. >> >> We have more time now than we had a few weeks ago. This is an >> opportunity to restart the discussion. We can refrain from pushing a new >> release (despite I would like this bug fix to be released officially) >> and take some time to think calmly. We could also push 3.2 with only the >> fix > > What about 3.1.1 with just the fix for this, then possibly 3.2 or > direct to 4.0.
As you want. I don't like adding too many sub-release numbers, just as if someone fears jumping to next version. I remember some Sun products and Perl versions that end up with something like 5 release digits. Well, I don't really care, so it can be 3.1.1 if people prefer that. Luc > > Phil >> and without any revamp and start thinking about 4.0 with a redesign >> of these two main area: optimization and sparse linear algebra. >> >> If you could contribute to this discussion understanding we are not >> experts of this field and we cannot do it by ourselves, it would be great. >> >> best regards, >> Luc >> >>> Thanks, Konstantin >>> >>> On Dec 28, 2012, at 11:27 AM, Phil Steitz <phil.ste...@gmail.com> >>> wrote: >>> >>>> On 12/28/12 8:12 AM, Dimitri Pourbaix wrote: >>>>> Luc, >>>>> >>>>>> So in order to make sure I understand your point, you would be >>>>>> OK if I deprecate the non-diagonal weights, in which case users >>>>>> needing this would have to implement it themselves by >>>>>> premultiplication (as both you and Konstantin seem to >>>>>> propose)? >>>>> Yes, exactly. >>>>> >>>>>> Sure, but for the record the feature was also a last minute >>>>>> change. This was discussed on the list, and the final decision >>>>>> was to add this feature despite the release was close. No >>>>>> wonder we failed to test it thoroughsly. >>>>> Last minute? I have been discussing this with Gilles for >>>>> several months. >>>> Relevant project discussion happens *on this list* >>>>>> We don't expect our releases to be perfect. We do our best, >>>>>> with the resources we have. >>>>> I perfectly understand this but focusing those resources less on >>>>> rules and more on real cases might help. >>>> As stated before, you are more than welcome to *become* one of >>>> these resources. >>>> >>>> Phil >>>>> Regards, Dim. >>>>> ---------------------------------------------------------------------------- >>>>> >>>>> >>>>> >> Dimitri Pourbaix * Don't worry, be happy >>>>> Institut d'Astronomie et d'Astrophysique * and CARPE >>>>> DIEM. CP 226, office 2.N4.211, building NO * Universite Libre >>>>> de Bruxelles * Tel : +32-2-650.35.71 Boulevard du >>>>> Triomphe * Fax : +32-2-650.42.26 B-1050 >>>>> Bruxelles * NAC: HBZSC RG2Z6 >>>>> http://sb9.astro.ulb.ac.be/~pourbaix * >>>>> mailto:pourb...@astro.ulb.ac.be >>>>> >>>>> --------------------------------------------------------------------- >>>>> >>>>> >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >>>>> For additional commands, e-mail: dev-h...@commons.apache.org >>>>> >>>>> >>>> >>>> --------------------------------------------------------------------- >>>> >>>> >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >>>> For additional commands, e-mail: dev-h...@commons.apache.org >>>> >>> >>> --------------------------------------------------------------------- >>> >>> >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >>> For additional commands, e-mail: dev-h...@commons.apache.org >>> >>> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >> For additional commands, e-mail: dev-h...@commons.apache.org >> >> > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > For additional commands, e-mail: dev-h...@commons.apache.org > > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
