2011/1/24 Lui ## <[email protected]>
> First of all: Thank you very much everybody for the vast number of
> replies! I really appreciate your help! I didn't expect so many
> responses!
>
> @ Guillaume Yziquel: Thank you very much for your quick responses and
> keeping track of the answers! I have to admit that I know very little
> about SDPs, so please excuse my stupid question: am I able to solve
> the Markowitz portfolio (at given risk, so w x Cov x w' with target
> function w x E(r)) ? Especially when my covariance matrix is changing
> and I need to have an optimizer that just uses the vektor E(r) and the
> matrix (Cov) as Input. Is that still possible when the my target
> function (maximize) is also in a quadratic form ( e.g. w x MATRIX x w)
> - without having to transform the problem manually? Thanks again for
> your great help!
>
> @ Daniel & Dave: Thank you very much for your links! The paper is
> really great and I have already started implementing the DE
> algorithm...
DEoptim is co-developed by Brian, so he is probably one of the first person
we should send our THX :)
best regards,
daniel
> Do you have any experience with the parameters with
> respect to PF optimization? The portfolio I am looking at is quite
> large (400+ stocks) and the algorithm is converging quite slowly (e.g.
> for the minimum risk portfolio). I tried NP = 6000, iterations at
> 2000.
>
> @Pat: Thank you very much for the link! I will take a look at it after
> "playing around with GAs and DEs a little". The reason is that I
> currently have a quadratic program and quadratic constraints but the
> constraints might become a little bit "ugly" (hold portfolio turnover
> in a certain range, assets from certain asset classes should only have
> a certain weight,...), so I want to be a little bit flexible...
>
> @Brian: I actually had troubles finding a solver for quadratic
> problems and quadratic constraints. I think quadprog was intended for
> quadratic problems with linear constraints or am I mistaken? I tried
> to get Rscop run but had problems installing the library. The solvers
> for linear problems and quadratic constraints as described in the
> fPortfolio package did not work out the way I wanted them either
> (there were some threads in R-Sig-Finance on that topic... But as my
> constraints will probably get more complex, or I will want to try out
> new ideas quickly I think I will go with the GAs/DEs first (unless you
> have a good recommendation for a flexible / easy to modify solver that
> is even aimed a little at portfolio problems
>
> @Ulrich: Thanks for the link! I see that genoud was used here - do you
> have any suggestions in terms of penalty functions for portfolio
> problems?
>
>
> Just to give you an overview on what I am trying to achieve:
>
> I am working on an investment strategy and want to compare it to
> Markowitz (with the risk level being the same...) Therefore I am
> currently trying implement Markowitz with GAs or Deoptim. I found
> going the "dirty" way in solving min w x Cov x w' with a target return
> saves me the pain from quadratic constraints but leaves me with many
> points on the efficient frontier to calculate - if I want to find an
> optimal E(r) for a given sigma (which I currently find most suitable,
> as both portfolios should have the same risk). That approach is not
> very "lean" and nice. My investment strategy leaves me (in the
> simplest form) with a quadratic problem (and the quadratic constraints
> still remain - since I am interested in the Variance).
> As there is lots of "try and try again" I appreciate the flexibility
> of "more general complex problem solvers" as the problem may get more
> complex with the constraints.
>
> I currently face the problem that the target sigma I want to achieve
> is kind of far from what the algorithms give me... I suspect the
> penalty function is the "problem". Do you have suggestions for good
> penalty function?
> I already "cut out" the sum(w) = 1 constraint by adding w <- w /
> sum(w) (see DEoptim paper). Currently, my penalty function looks like
> this:
>
> return <- return(w)
> variance <- variance (w)
>
> penalty_faktor = 20
> penalty <- max((variance - targetvariance)/targetvariance,0)
>
> if (((variance - targetvariance)/targetvariance) < 0.1){
> penalty_faktor = 1
> penalty = 0
> }
>
>
> ret <- (penalty*100)^penalty_faktor - return
>
> I dont care so much if the true variance is little bigger (10%) and
> found if-then routines "spitting" out 99999 values if the constraints
> are not met to be very inefficient... If somebody has suggestions for
> good penalty function - please let me know!
>
> Have a great weekend!
> Lui
> On Sun, Jan 23, 2011 at 5:32 PM, ArdiaD <[email protected]> wrote:
> > This might be of interest:
> > http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1584905
> > Regards
> > Dave
> >
> > On 01/23/2011 11:23 PM, Ulrich Staudinger wrote:
> >> Lui,
> >>
> >> you can also have a look at
> >>
> http://aqr.activequant.org/index.php/2010/08/genetically-optimizing-a-trading-system/for
> >> inspiration on how to genetically optimize a trading system, whether
> >> it's quadratic or not. It's just some snipplet but exemplifies it pretty
> >> well ...
> >>
> >> Regards,
> >> Ulrich
> >>
> >>
> >> On Sun, Jan 23, 2011 at 11:15 PM, Guillaume Yziquel <
> >> [email protected]> wrote:
> >>
> >>> Le Sunday 23 Jan 2011 à 15:56:40 (-0600), Brian G. Peterson a écrit :
> >>>> On Saturday, January 22, 2011 04:33:09 pm Lui ## wrote:
> >>>>> Dear group,
> >>>>>
> >>>>> I was just wondering whether some of you have some experience with
> the
> >>>>> package "rgenoud" which does provide genetic algorithms for complex
> >>>>> optimization problems.
> >>>> <...>
> >>>>
> >>>>> What is your general experience? Did you ever try solving the
> >>>>> Markowitz portfolio with the rgenoud package?
> >>>>> I know that there are good solvers around for the qudratic
> programming
> >>>>> problem of the markowitz portfolio, but I want to go into a different
> >>>>> direction which translates into a quadratic problem with quadratic
> >>>>> constraints (and I havent found a good solver for that...).
> >>>>>
> >>>>> I am interested in your replies! Have a good weekend!
> >>>> As others have already said, for a quadtratic problem with quadratic
> >>>> constraints, there is an exact analytical solution.
> >>> I wouldn't qualify dual interior point methods as an "exact" solution,
> but,
> >>> yes, that's the basic idea: they're better suited for that.
> >>>
> >>>> In these cases, you will be much better off both from a performance
> and
> >>>> accuracy perspective in using a quadratic solver (quadprog is most
> often
> >>>> applied in R, see list archives and many packages for examples).
> >>> Is quadprog a second-order cone programming solver? If that is the
> case,
> >>> yes, it probably solves quadratic objective function with quadratic
> >>> constraints faster and with more accuracy than a full-fledged SDP
> >>> solver.
> >>>
> >>>> Other portfolio problems may be stated in terms of linear solvers,
> which
> >>> will
> >>>> likewise be faster than a global optimizer for finding an exact
> >>> analytical
> >>>> solution.
> >>>>
> >>>> If, however, your portfolio problem is non-convex and non-smooth, then
> a
> >>>> genetic algorithm, a migration algorithm, grid search, or random
> >>> portfolios
> >>>> may be a good option for finding a near-optimal portfolio. If this is
> >>> your
> >>>> true goal, perhaps you can say a little more about your actual
> >>> constraints and
> >>>> objectives (and use assets that are outside of your true area of
> >>> interest,
> >>>> such as the S&P sector indices).
> >>> Yes, the problem structure often gives good insight as to which method
> >>> to apply. It may be noted, however, that quite a lot of non-convex
> >>> problems may be transformed into convex ones. And using some relaxation
> >>> methods, you can often use SDPs to optimise multivariate polynomial
> >>> objective under multivariate polynomial constraints, without too many
> >>> convexity hypothesis.
> >>>
> >>> SDPs are not always easy to manipulate, but they do solve a broad range
> >>> of optimisation problems.
> >>>
> >>>> Regards,
> >>>>
> >>>> - Brian
> >>> Best regards,
> >>>
> >>> --
> >>> Guillaume Yziquel
> >>> http://yziquel.homelinux.org
> >>>
> >>> _______________________________________________
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> >>>
> >>
> >>
> >
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