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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0
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1answer
174 views

My Baum-Welch algorithm is very slow. Is it due to Mathematica?

I've also posted this question here, since I'm not sure which community is more adequate for this type of question. I've programmed imperatively the Baum-Welch algorithm for a 2 state hidden Markov ...
5
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1answer
235 views

A more perfect Union[]

I was doing a Project Euler problem with my class, and found the following weird fact: Union[] of a list of some 50 million numbers (of which only around 15000 were ...
14
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6answers
1k views

Integers which are the sum of both two and three consecutive squares

This is a math problem I came across the other day: $365$ can be written as a sum of two and also three consecutive perfect squares: $365=14^2+13^2=12^2+11^2+10^2$ What is the next ...
5
votes
1answer
91 views

Speedup of KL Divergence by Monte Carlo Simulation

I started with Mathematica about just a week, so I don't know how to take all of this environment. What I want to know is if there is a way to speedup my code to compute the KL-Divergence of Gaussian ...
9
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3answers
233 views

Improving selection of elements from large multidimensional array

Frequently in my profession I deal with large arrays of data. Typically these are mixed types including integers, strings, dates, and reals. To recreate a typical data array: ...
1
vote
1answer
137 views

How smart is Solve? Figuring out what tricks I should try

I'm trying to solve a large system (~10000) of linear equations using Solve, but the process keeps failing. As-is, I don't know whether it's failing because it's using too much memory or too much time ...
5
votes
2answers
131 views

Optimizing code containing an infinite sum

I have the following expression. It's based on the negative-log-likelihood of a Poisson-Gaussian noise model, i.e. a convolution of a Poisson & Normal distribution. The value $x_{i}$ is the ...
14
votes
2answers
448 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 ...
9
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2answers
186 views

Export[] performance

Consider this sequence of commands: ...
3
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1answer
103 views

Listable on first level [duplicate]

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
160 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
243 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
112 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
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0answers
235 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
267 views
2
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1answer
75 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
73 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
144 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 ...
15
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2answers
251 views

A bug in Commonest in version 10

Bug introduced in 10.0.0 and fixed in 10.0.2 m_goldberg demonstrated that in Mathematica 10 Commonest does not behave as the documentation indicates that it ...
5
votes
1answer
400 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
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3answers
304 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
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0answers
79 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
95 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
151 views

Optimizing a function containing a complex exponential

I've noticed the following significant different in performance for different formulations of the same function: ...
17
votes
0answers
226 views

Can code optimize code?

Are there functions, programs or packages that deal with optimizing mathematica code i.e. re-writing ineffecive or convoluted code. -This question has haunted me since I joined SE. The background for ...
1
vote
1answer
157 views

Strange behavior of function (memory leaks)

I have some funtion: ...
2
votes
2answers
109 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
78 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
229 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} ...
16
votes
2answers
271 views

Combining images with CUDA

SMALL UPDATE: This question is left as unanswered, because none of the existing answers as of yet actually use CUDA (though, whilst being very useful). 2nd Edition: To make it a bit more clear, and ...
23
votes
2answers
495 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
263 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
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0answers
207 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 ...
16
votes
1answer
435 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 ...
7
votes
1answer
225 views

Is there a faster way to Map an Association?

Consider mapping an existing Association in a manner such as this: ...
0
votes
0answers
141 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
404 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
66 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
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0answers
84 views

strange timing behavior

The following code is from a book about Mathematica. ...
2
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3answers
155 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
228 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
42 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 ...
7
votes
1answer
65 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
101 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
83 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
216 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 ...
28
votes
1answer
990 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
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0answers
101 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
404 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
106 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 ...