Skip to main content

performance tuning - Manipulate executes expressions multiple times


I am using Manipulate for a rather intricate front end for data visualization. I was getting very sluggish performance and was able to boil the problem down to a very similar question (Why does Manipulate execute the expression twice?). The suggestions of using ContinuousAction->False and TrackedSymbols does not seem to work in this case.



Let's simplify the problem by producing a simple array of numbers and mapping a simple function through them. The array of numbers needs to change dynamically, here we just change the length based on a manipulation parameter, i:


manipulateSlow[] := Module[{data, updated},
  Manipulate[
    Print[i];
    data = RandomReal[{0, 1}, 100*i];
    updated = Map[Sin, data];
  , {i, {1, 2, 3}}]]

manipulateFast[] := Module[{updated},
  Manipulate[

    Print[i];
    updated = Map[Sin, RandomReal[{0, 1}, 100*i]];
  , {i, {1, 2, 3}}]]

When one plays with the parameter i in manipulateSlow


manipulateSlow[]

the code internal to Manipulate is called multiple times. This is in contrast to manipulateFast


manipulateFast[]


where when fiddling with the parameter i the code internal to Manipulate is only called once per manipulation.


This example is, of course, just a toy. In my real application the process of RamdomReal is replaced by a much slower data reading function. Calling it multiple times is not an option.


EDIT:


I lied when previously saying that TrackedSymbols does not work. The follow fixes the issue of multiple Print evaluations.


manipulateFixed[] := Module[{data, updated},
  Manipulate[
    Print[i];
    data = RandomReal[{0, 1}, 100*i];
    updated = Map[Sin, data];
  , {i, {1, 2, 3}},TrackedSymbols :> {i}]]


I must be confused about how TrackedSymbols changes the evaluation process. What is happening inside of manipulateFast that does not cause the evaluation to occur twice?




Comments

Post a Comment

Popular posts from this blog

functions - Get leading series expansion term?

Given a function f[x] , I would like to have a function leadingSeries that returns just the leading term in the series around x=0 . For example: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x)] x and leadingSeries[(1/x + 2 + (1 - 1/x^3)/4)/(4 + x)] -(1/(16 x^3)) Is there such a function in Mathematica? Or maybe one can implement it efficiently? EDIT I finally went with the following implementation, based on Carl Woll 's answer: lds[ex_,x_]:=( (ex/.x->(x+O[x]^2))/.SeriesData[U_,Z_,L_List,Mi_,Ma_,De_]:>SeriesData[U,Z,{L[[1]]},Mi,Mi+1,De]//Quiet//Normal) The advantage is, that this one also properly works with functions whose leading term is a constant: lds[Exp[x],x] 1 Answer Update 1 Updated to eliminate SeriesData and to not return additional terms Perhaps you could use: leadingSeries[expr_, x_] := Normal[expr /. x->(x+O[x]^2) /. a_List :> Take[a, 1]] Then for your examples: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x), x] leadingSeries[Exp[x], x] leadingSeries[(1/x + 2 + (1 - 1/x...
Post a Comment
Read more

mathematical optimization - Minimizing using indices, error: Part::pkspec1: The expression cannot be used as a part specification

I want to use Minimize where the variables to minimize are indices pointing into an array. Here a MWE that hopefully shows what my problem is. vars = u@# & /@ Range[3]; cons = Flatten@ { Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; Minimize[{Total@((vec1[[#]] - vec2[[u[#]]])^2 & /@ Range[1, 3]), cons}, vars, Integers] The error I get: Part::pkspec1: The expression u[1] cannot be used as a part specification. >> Answer Ok, it seems that one can get around Mathematica trying to evaluate vec2[[u[1]]] too early by using the function Indexed[vec2,u[1]] . The working MWE would then look like the following: vars = u@# & /@ Range[3]; cons = Flatten@{ Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; NMinimize[ {Total@((vec1[[#]] - Indexed[vec2, u[#]])^2 & /@ R...
Post a Comment
Read more

How to remap graph properties?

Graph objects support both custom properties, which do not have special meanings, and standard properties, which may be used by some functions. When importing from formats such as GraphML, we usually get a result with custom properties. What is the simplest way to remap one property to another, e.g. to remap a custom property to a standard one so it can be used with various functions? Example: Let's get Zachary's karate club network with edge weights and vertex names from here: http://nexus.igraph.org/api/dataset_info?id=1&format=html g = Import[ "http://nexus.igraph.org/api/dataset?id=1&format=GraphML", {"ZIP", "karate.GraphML"}] I can remap "name" to VertexLabels and "weights" to EdgeWeight like this: sp[prop_][g_] := SetProperty[g, prop] g2 = g // sp[EdgeWeight -> (PropertyValue[{g, #}, "weight"] & /@ EdgeList[g])] // sp[VertexLabels -> (# -> PropertyValue[{g, #}, "name"]...
Post a Comment
Read more