Questions about optimizing code for faster results, or how to do faster computations.

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1answer
31 views

Speeding up EPS exporting ?

I'm using Mathematica 10 to render some figures, and I'm noticing some strange behaviour with EPS figures. I'm making figures like the one below in EPS format. And to do so, I use some code like ...
-1
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0answers
23 views

How could I speed up a code including a Module with many functions

I have implemented a big formula through the mathematica function Module. Within this module a lot of definitions are made (i.e. function[x_]:=). The code are working well but it is too slow. I am ...
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0answers
93 views

How can I speed up this NM optimization? Most delay seems to be due to long analytic expression

I am struggling with computational speed of a NelderMead optimization. Nevertheless my impression is that I lose lots of speed not only due to the NM optimization itself but rather to for instance ...
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0answers
57 views

Optimising prime number test code

Is it possible to speed-up this code ? Also, It would be great if people could test this algorithm. I only have a Raspberry Pi to test it on, so I can't be certain it's not a strong probable prime ...
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0answers
42 views

Broad Phase Collision Detection with Mathematica and using CUDA

In this and this post, I asked the question about a fast sweep and prune algorithm implementation for broad phase collision detection. To further speed up things a CUDA implementation would be even ...
2
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0answers
67 views

StreamPlot slow in version 10

In version, 10 StreamPlot seems to calculate many more points along each streamline than necessary, compared to version 7. For example, from Mathematica ...
2
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1answer
81 views

speeding up creation of SparseArray

I have to create the following sparse arrays, which are reshaped in a two dimensional matrix, so that i can use the build in Dot[] function to do a kind of ...
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0answers
32 views

Speeding Up the Numerical Integration of a Product of Numerical Integrands with NIntegrate

I need to solve a set of coupled integral equations within a self-consistent cycle. The final result will be functions, say $A(x)$ and $B(x)$, which are related to each other by some integrals which ...
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0answers
24 views

FindMaximum slow for fixed parameters

I hope my problem can be solved by just showing you this tiny part of my code which does not run on its own. I have an optimization problem and want these functions to work on various data sets. ...
7
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1answer
132 views

Relaxation of Mass-Spring System with Pinned Masses

Problem Assume that four masses are connected to each other by springs while two of them are pinned down at their initial positions. Find the position of masses when system is at its minimum ...
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0answers
74 views

Collision detection algorithm (discrete) with sweep and prune algorithm for periodic boundary conditions

EDIT: Question Updated with solution approach, but solution much slower than original implementation. Any ideas to speed up implementation? In the discussion on collision detection (see here) I asked ...
2
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3answers
98 views

Finding minimum of a list of pairs

Sometimes I need to find the Min of a list, whose elements are lists (say of two elements, a pair). Given that Min does not have the option to indicate a sorting function like Sort, I elaborated the ...
5
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1answer
139 views

Functional-programming virus infection

Update: The question may seem too broad, but the answer provided by belisarius responds perfectly to the question, as the use of $ListConvolve$ and $NestList$ meets the desired criteria in in addition ...
0
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0answers
86 views

Low CPU usage. How to increase it? Should I?

I'm running a programme, and below are some graphics from the resources monitor from windows 8, while running my programme in version 9 of mathematica. Sorry for the foreign writings in the pics, but ...
0
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1answer
49 views

How to speed up ReplaceAll in Table?

I am writing a code which solve a list of equations and then create a Table with resulst of equation solving. In applications where I use this code, I create a bunch of equations and my computations ...
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0answers
24 views

Tricks to speeding up optimisation of a function involving a heavy integration

This is the code, and energycoeffs[] is the function that takes in a dxd matrix and spits out a scalar value. ...
6
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0answers
95 views

Efficient image stacking

I have a list of lists of images that I would like to stack and create mean images for each list of images. Images are .jpg files 2592x1944 pixels large. Each list ...
3
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2answers
57 views

How do I apply a ColorDataFunction[] to a grayscale image? [duplicate]

Suppose I have a 2D array im of real values between 0 and 1, representing a grayscale image. I can turn im into an image very ...
0
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0answers
38 views

Retrieving a Portion of Webpage Code using URLFetch

The URLFetch command is very useful for pulling the entire html source of a given webpage, however, if one wanted to speed up the process, by only requesting a ...
2
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2answers
60 views

What is the fastest way to get notebook CellGroups / Cells structure?

So the question is how to get this kind of information: from This is one of my ideas: ...
9
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1answer
120 views

Slow work of SQLInsert with MS SQL Server in V10

This question is very similar to: Slow work of SQLInsert with SQLite, but for MS SQL Server. Unfortunately the use of SQLBeginTransaction and ...
1
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1answer
55 views

Is this caused by meomory usage ? (Something odd/hard to describe)

I really can't make a "smaller" example, but the files are here, for the data and for the notebook. It will cost a LOT of memory, up to 30G of RAM (maybe more). Here is the problem, (from a Linux ...
0
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0answers
115 views

CPU usage ~18%, but Mathematica is fully running

I run some very long Mathematica code, and the CPU usage of the kernel is 18% only. Why is not all of the CPU used, can I find the reason easily? Are there known ways to tell Mathematica to use more ...
4
votes
5answers
291 views

Check whether array has only constant entries?

I have an array arr with n entries. Now I want to check whether ...
2
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1answer
126 views

How to speed up my code about Divisors?

This code is about PE496 In[21]:= ParallelSum[n*Count[Divisors[n^2], a_ /; n < a < 2 n], {n, 1, 10^5}] // AbsoluteTiming Out[21]= {5.987342,10724527832} I ...
11
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2answers
249 views

Choose between `Apply` and `Map`

Even though this might be too general question(or not answerable), I want to get some advice here. I apologize in advance if it is not a relevant question. I frequently have to process large list of ...
1
vote
3answers
100 views

Speed up NIntegrate, which takes eigenvalues from another function

I have simplified my problem here, in my actual problem the matrix is much bigger which makes it impossible to find eigenvalues analytically. So, I chose standard BCS problem (2x2 matrix) to ...
0
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1answer
90 views

How to speed up execution of this function?

How can I speed up the execution of following function, specifically for larger values of n? ...
4
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1answer
95 views

Why is C-compiled (but not WVM-compiled) code so slow in Manipulate?

Here is a small section of code from this SE question which computes the real part of the dilogarithm (the upper limit of the sum is increased for demonstration purposes): ...
2
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1answer
93 views

Optimizing alphametrics code

First of all, thank you all in this great community. I have been reading a lot of threads about Mathematica optimization learning things like using Compile ...
4
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1answer
112 views

How do I understand this big difference in speed:

A friend of mine found a huge difference in runtime speed between these two ...
4
votes
1answer
231 views

Mathematica 10 issue: working with Entities slows down recurrence equations [duplicate]

I was looking at the Mathematica code given at http://community.wolfram.com/groups/-/m/t/326240 where example code is given to simulate the spreading of a supposed Ebola outbreak in Nigeria: ...
3
votes
2answers
204 views

Help at speeding up simplification/nested symbolic integration

I have the following problem: I want to compute an integral of the form $$\int\limits_0^{t_g}\mathrm{d}t_2\int\limits_0^{t_2}\mathrm{d}t_1\left[A(t_1),A(t_2)\right],$$where $\left[B,C\right]=BC-CB$ is ...
7
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0answers
94 views

How to make Graphics3D with multiple lighting sources being rendered faster

I have a very "precise"(through setting "SpherePoints") Sphere illuminated by hundreds of random color lighting sources. The ...
0
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1answer
67 views

Duplicate values n-times [closed]

I already asked how I can take the list {1,2,3} and get {1,1,1,2,2,2,3,3,3} out of it, adding degeneracy to the problem. So far ...
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0answers
49 views

More on performance of Sum[]

There is an interesting discussion on performance of Sum[] in this question. I actually wanted to reproduce findings from this answer. So, I entered: ...
1
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1answer
51 views

Speed optimization of Mean calculation in a previous calculated data range

I have following problem: My calculations work quite well with the shown testdata, the only problem is the speed of it. My original dataset is about 64000 datapoints, and it takes several minutes to ...
5
votes
3answers
253 views

The speed of Sum[] varies strangely

I was curious about the difference in speed between Total and Sum. I found out Total was ...
2
votes
1answer
62 views

How to handle Indeterminate TimeConstrain

I have to use Timeconstrained[aux] first for avoid some bigs calculation that dont need and it use a lot of time of calculate, so i can't do this. ...
5
votes
1answer
473 views

Over 30mins to generate the first eigenvector?

Is it normal for Mathematica to take over 30mins to try to compute the first eigenvector of a 100x100 matrix? The matrix is reasonably sparse - about 90% of the cells are 0s and each column sums to ...
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0answers
67 views

Improve on timing of NMinimize

I got a little performance problem with the function NMinimize (it takes mathematica approximately 10 minutes to compute the results). Here i s my sample code: ...
2
votes
1answer
134 views

Neighbourhood - Calculations

SeedRandom[0]; n = 5; (m = N @ RandomInteger[{1, 3}, {n, n}]) // MatrixForm result1 = MeanFilter[m, 1] // MatrixForm ...
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0answers
58 views

Speed up numerical optimization (for plotting and solving)?

Briefly speaking, I want to plot a function PIfun[], which its value is based on numerical optimization using NMaximize. It ...
17
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1answer
301 views

Why some built-in functions are slow

I just wonder why some built-in functions are slower compared to some other ways using more than one built-in functions for doing same job. consider this example: ...
4
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2answers
423 views

Colorize Grayscale Image

I have a grayscale image that contains two objects. The grayscale pixel values can be divided into three intervals where two of them represent objects and the third represents the background. The ...
21
votes
1answer
443 views

Total much slower in version 10

Issue introduced in version 10, fixed in 10.0.2 Compilation nowadays may give very fast functions. Here is an example for finding the sum of a list of machine numbers, just as the built-in function ...
2
votes
1answer
140 views

2D Fourier transform of a few (4) disjoint discs on a plane

I'd really appreciate some advice. Short Version I'm trying to calculate the following $$ ...
6
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1answer
309 views

Collision detection algorithm (discrete) with sweep and prune algorithm

For a more complex collision detection approach, I need an efficient (aka fast) algorithm to prune the elements by using boundary boxes. A classical algorithm is the so called sweep and prune (SAP) ...
3
votes
3answers
325 views

Faster Integer Approximation of pi

I'd like to speed up this calculation: First[Sort[Table[{k,Abs[Round[k/Pi]Pi - k]1.{k,1,100000}],#1[[2]]<#2[[2]] &]] The code above generates a list of ...
25
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3answers
3k views

Understanding differences between Maple and Mathematica in examples picked by Maplesoft

I am reading the document "How Maple Compares to Mathematica" found at http://www.maplesoft.com/products/maple/compare/HowMapleComparestoMathematica.pdf. On page 15 there is an example where ...