Questions on optimizing Mathematica code for higher performance. This may mean faster execution, lower memory usage or both. Not to be confused with mathematical optimization.

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12
votes
2answers
137 views

Better way to test that a matrix is upper-triangular?

Today, I got to thinking about how to test that a matrix was upper-triangular. So I had a try at it. Algorithm $\quad \quad a_{ij}=0 $ Or $i \leq j$ $\Rightarrow$ $True$ My solution is ...
5
votes
1answer
44 views

Export[] performance

Consider this sequence of commands: ...
3
votes
0answers
53 views

Listable on first level

I have some function which take List as input. f[l_List]:=someActions[l] I need apply this function to a list of lists. Now I ...
7
votes
1answer
123 views

Simpler code evaluating Dickman's function?

I've read here that Mathematica 10 can Obtain symbolic solutions to delay differential equations. Would that help in numericaly evaluating Dickman's function $\rho(u)$ ? It is a delay differential ...
7
votes
3answers
195 views

Issue with very large lists in Mathematica

I have a need to work with very large arrays of data in Mathematica. The length of the list is not known upfront. The typical size is a few hundred thousands elements and could easily go beyond a ...
3
votes
1answer
69 views

How to efficiently select elements from a Hash?

How can I write an efficient version of the following selection statement: Keys[Select[hash, # < constant &]]; // AbsoluteTiming hash can be made from: ...
3
votes
0answers
56 views

Fast principal component analysis

I'd like to speed up a principal value value analysis. The data contains a large set of vectors with a large dimension. Both are in the range of 1000. I want to obtain the loadings matrix for further ...
3
votes
1answer
114 views
1
vote
1answer
53 views

Faster way to extract partial data from AdjacencyMatrix

I am dealing with a lot of Graph objects. One task is to obtain an Id for each of them. So I first used ...
2
votes
0answers
68 views

Mathematica 10 loads too long time [duplicate]

After starting Mathematica 10 it hangs for about a minute before becoming operational. Internet connectivity is disabled. Start screen is disabled. What should I do? P.S. Opening any help page ...
5
votes
1answer
119 views

How to efficiently select element in a list of lists?

How can I write an efficient version of the following statement? Cases[list, {_, feature_} /; feature < constant]; // AbsoluteTiming List is of the form, list ...
12
votes
1answer
143 views

A bug in Commonest in version 10

Bug introduced in 10.0.0 m_goldberg demonstrated that in Mathematica 10 Commonest does not behave as the documentation indicates that it will. Concisely: ...
3
votes
1answer
322 views

Using Compile Function Options efficiently

While this gives general pointers, I want inputs on ground rules for improved performance of nested/interdependent compiled functions. sample problem: a, ...
2
votes
3answers
143 views

Alternatives to Append/AppendTo for generating a list in an interactive DynamicModule?

I have a stack of timelapse microscopy images that I am trying to segment frame-by-frame using some of Mathematica's image processing functions. I have created a little interactive DynamicModule with ...
3
votes
0answers
61 views

Efficient processing of Special Ordered Sets with LinearProgramming

I'm playing with integer linear programming, especially problems involving lots of constraints which would appear to be special ordered sets. Below is a toy example, three last rows of the matrix ...
0
votes
1answer
63 views

Unusual Slow Down with LocatorPane/DynamicModule

I have coded up a little interactive DynamicModule to help me with image processing/segmentation of stacks of timelapse microscopy images. I am experiencing a crippling slow down in the ...
4
votes
1answer
101 views

Optimizing a function containing a complex exponential

I've noticed the following significant different in performance for different formulations of the same function: ...
1
vote
1answer
93 views
2
votes
2answers
69 views

Improving the speed/efficiency of multiple (finite range) convolutions for a causal response plot

So I am looking at modelling the response of a system that is excited by multiple pulses over a period of time. The way to find the response at time t is to take the convolution between the impulse ...
1
vote
1answer
70 views

Faster code for solving an equation with parameters

I am new to Mathematica and wanted to solve an equation that depends on parameters. The code is below ...
2
votes
1answer
117 views

How can I reduce computation time while still obtaining a good approximation for my function?

I am new to any CAS (and Mathematica, for that matter) and new to StackExchange too, so forgive me and correct me on any mistakes. I have this function: $J_p=\sum_{m,n=1}^{\infty} ...
21
votes
2answers
437 views

Why is Query so much slower than Part?

Time for another of these(1),(2) as yet another new-in-10 function appears to have poor performance compared to older alternatives. This time: Query appears to be ...
1
vote
1answer
221 views

Performance of compiled functions (Project Euler No14)

I was playing around with the project euler problem 14. The solution I came up with is listed below as cf1. The solution works fine but I get the compiler warning: ...
1
vote
0answers
133 views

Speeding Up Image Processing Functions

I am working with stacks of 1024x1024 timelapse microscopy images that I am performing a series of image processing functions on to help segment each image. These functions include ...
15
votes
1answer
250 views

Speed up adding Poisson noise to an image

I'm simulating some images corrupted with Poisson noise, but I'm encountering a few problems with performance. According to the documentation on ImageEffect, one ...
5
votes
1answer
134 views

Is there a faster way to Map an Association?

Consider mapping an existing Association in a manner such as this: ...
0
votes
0answers
105 views

Improving the speed of evaluating Table with nested functions

I am a Mathematica novice working with a stack of 1024 x 1024 WatershedComponents (or MorphologicalComponents) label matrices ...
8
votes
4answers
291 views

Fast method to select matrix elements based on a vector of positions

There is an operation for which I have long wanted to find a better solution. Let: a be a matrix of dimensions $m\times n$ ...
1
vote
1answer
63 views

A code deal with Lists operation ---Needs optimizion

I have written some code to deal with lists, But the speed of the code is slow, Could Someone help me to speed up it? Probably could rewrite it with Functional Programming! Give me some ideas! The ...
0
votes
0answers
74 views

strange timing behavior

The following code is from a book about Mathematica. ...
2
votes
3answers
110 views

Speeding Up Replacing of Labels in Large Matrix?

I am Mathematica novice and am trying to find a fast way to replace labels in some rather large matrices (512x512 or 1024x1024) that have resulted from segmenting images with WatershedComponents or ...
1
vote
0answers
89 views

Speeding up NDSolve for system of differential equations

I am wondering if there is a way to speed up this function that solves a system of ordinary differential equations with NDSolve? Thus far I've tried specifying a few different methods such as LSODA, ...
0
votes
1answer
36 views

Timing enclosed by Manipulate not working [closed]

Manipulate[Timing[Show[somegraphs[[1 ;; i]]]], {i, 1, 500, 1}] (in Mathematica 8) This is the last line of my function f[x_]:= Module[....]. I am trying to combine a list of graphs into a single ...
6
votes
0answers
51 views

Issuing user-defined messages takes a long time (Message is slow)

Issuing messages takes a very long time in version 9 and version 10. Can others reproduce this? Is there a fix? Update: This is slow only when using the front end, but not when running the kernel ...
1
vote
1answer
51 views

Warning and Errors during Compile

I defined a compiled function cf = Compile[{{x, _Integer}, {n, _Integer}}, z = (n^x); Binomial[n, #]* StirlingS2[x, #] *(#!)/z & /@ Range[x]]; and I ...
2
votes
3answers
73 views

Reduction of repetitive calculations in Table

If I generate two tables inside a function which are function[n_, x_, y_]:=( table1 = Table[i* x/n^x, {i,1,n}]; table2 = Table[i* y/n^y, {i,1,n}]; ) where ...
6
votes
1answer
138 views

Optimizing the front end on the Raspberry Pi

Using Mathematica's Front End on the Raspberry Pi is truly a test of one's patience. The most basic of notebooks become unresponsive after seemingly trivial additions to the notebook. Consider the ...
20
votes
1answer
603 views

Mma 10: Half the parallel power (Macs)?

Here is a comparison of the parallel kernels launched under Mathematica under v9 and v10, on the same identical current 2014 R2-D2 Mac Pro ... [ Update: Valerio has commented that the same issue ...
0
votes
0answers
88 views

Timing: how make a program to work faster using built in functions and tables

I want to improve my code to make it working faster even for very large numbers. ...
12
votes
1answer
244 views

the more effective method to find 21 digits armstrong number

In recreational number theory, a narcissistic number (also known as a pluperfect digital invariant (PPDI), an Armstrong number(after Michael F. Armstrong) or a plus perfect number) is a number that is ...
0
votes
0answers
87 views

Complex Convolution

I am attempting to integrate a convolution variable using the following code. However, the program is taking too long to complete the integration. Does anybody have any coding tips that may make ...
2
votes
2answers
167 views

Alternative for MapThread in listable functions

How can I rewrite this more efficiently taking advantage of flo, dem, and Nsup being ...
6
votes
4answers
219 views

Position of Subsets in a List

I have a particular list of integers and a matrix whose entries are lists. Say I know that my particular list is a subset of at least some of the elements in the matrix. I want to find an efficient ...
1
vote
0answers
77 views

Speeding up the numerical integration of a certain function

I'm using the following function f[t_] := 3/4 t^-3 NIntegrate[(x^4*Csch[x/2]^2), {x, 0, t}, Method -> {Automatic, "SymbolicProcessing" -> 0}]; I ...
5
votes
1answer
224 views

More efficient Omnibus number determination?

Amusing myself with concepts from "Omnibus Sequences, Coupon Collection, and Missing Word Counts", in particular the sequences. To paraphrase the concept, a string is k-Omni over some alphabet a if ...
0
votes
0answers
68 views

Timing Differences

In More efficient implementation for comparing coefficient lists in a Do-loop link, george2079 posts in his first answer a piece of code that takes 352 seconds to compute. When I run this same piece ...
1
vote
0answers
82 views
23
votes
3answers
688 views

Smooth Peter de Jong attractor

Today I was playing with Peter de Jong attractor. At the bottom of the page I've linked there are beautiful examples like: My attempts are not so great: It is around 10^5 points. For more than ...
2
votes
3answers
243 views

Alternative ways to AppendTo and Delete in a While loop

Is there an alternative way to do AppendTo and Delete and also replace k0 during every ...
0
votes
0answers
47 views

Expectation taking unusually long to evaluate

I am trying to evaluate an expectation, but it is taking an extremely long time although the expression itself should not be too complicated. My code is ...