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Jul
29
comment What is the difference between Set and SetDelayed?
@FaysalAberkane I am not sure I understood, but y[x_]=Sin[x] re-evaluates (say) Sin[5.] no matter how many times you say y[5.]. It doesn't cache values at all in this sense, while y[x_]:=y[x]=Sin[x] remembers that y[5.] is whatever it is (ie it only evaluates Sin[5.] once).
Jul
29
revised What is the difference between Set and SetDelayed?
added 290 characters in body
Jul
29
comment What is the difference between Set and SetDelayed?
@Mr.Wizard good point, will fix it
Jul
29
answered What is the difference between Set and SetDelayed?
Jul
28
comment Image Processing: Isolating areas of an image with internal irregularity
Both belisarius and Vitaliy have answered your original question; if you feel they haven't, please try to clarify why. Your update is a different question (and probably way too general; is the white balance going to be correct? the colour of the nails always the same? their size always constant?). it's underspecified
Jul
28
comment Find subexpression to minimize leafcount after replacment with temporary variable
you could also use Experimental`OptimizeExpression[$expr]
Jul
27
comment Efficient Langevin Equation Solver
@Gabriel I suppose it can be guessed by analogy to Kibble-Zurek type arguments (well, they don't really apply since there's not actual transition, but maybe one could estimate the domain size like this--but maybe not).
Jul
27
comment Efficient Langevin Equation Solver
if I start at a high temperature and decrease it at a fixed rate, can I predict the characteristic size of the domains? is it related to the rate?
Jul
27
comment Efficient Langevin Equation Solver
@LeonidShifrin Yes, I think you pointed this out to me once before. I find it more readable though (small brain) so I'll leave it. thanks
Jul
26
comment Efficient Langevin Equation Solver
You mention that "A follow up would be to extend all this to systems of Langevin equations". What would you like that to look like? Clearly you know that you could just use vectors to obtain a solution for a single realization of the noise in the same way you are doing it now. What more would you want? To do it for many realizations with a single NestList?
Jul
26
revised Efficient Langevin Equation Solver
added 1255 characters in body
Jul
26
revised Efficient Langevin Equation Solver
added 80 characters in body; added 110 characters in body
Jul
26
comment Efficient Langevin Equation Solver
@sebhofer a copy of the package :)
Jul
26
comment Efficient Langevin Equation Solver
Yes you're right, I screwed up. Let me fix it later. The only advantage is that it is trivially parallelizable and it scales much easier (at least, for me). Try to solve the discretised KPZ equation (which is notorious for slow convergence) for large systems and thousands of runs and you will see what I mean. For obtaining intuition, though, I agree that the Nest approach is neater. In practice, anyway, for something as simple algorithmically as this, C is much faster and not very hard to code if performance is needed.
Jul
26
comment Efficient Langevin Equation Solver
quizz: what package was used for figs 2 and 3 of this?
Jul
26
answered Efficient Langevin Equation Solver
Jul
26
comment Efficient Langevin Equation Solver
@R.M it can be parallelized if you calculate each realization independently (I ended up doing this when I was working on stochastic processes a few years back)
Jul
24
answered Sharp ListDensityPlot
Jul
23
answered How to generate table without comma and bracket or get rid of those?
Jul
19
comment How can I access documentation from the Workbench?
apparently, we can't. would be nice if someone has a way though, that's the main problem I have with workbench.