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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4
votes
1answer
205 views

Very slow mathematica finite differences

I have a simple code which solves an equation by an explicit method (FTCS). It takes mathematica several minutes (mathematica 10.0.2) to finish the calculation while the same code in Fortran runs less ...
24
votes
4answers
5k views

Finding Local Minima / Maxima in Noisy Data

I'm trying to find local minima / maxima in noisy data, consisting of data values taken at certain time intervals. Ideally, the function should take a pair of lists (one containing time values and one ...
1
vote
1answer
177 views

Slow evaluation of NIntegrate when used as a pure function

I asked a perhaps related question here. Here is my code in below. The goal is that to define a function which must be integrated numerically. The function itself first is calculated over different ...
1
vote
0answers
21 views

What is the most efficient method to find a single eigenvector with eigenvalue that is numerically 0?

I need to find an eigenvector of a (numerically calculated) square matrix M corresponding to the eigenvalue 0. The methods I know are ...
5
votes
1answer
166 views

Slow exponential evaluation over lists

This question,which is still unanswered, might be relevant because it involves NIntegrate over lists and it also has Exp. In ...
4
votes
1answer
75 views

How to get probabilities for multinomial & hypergeometric distribution ranges more quickly?

I often need to calculate the probability of a result from a multinomial distribution falling within some range, e.g., the maximum of the categories having an upper bound, or a lower bound for the ...
3
votes
0answers
69 views

Decrease computation time of module [closed]

I need to compute the exponential of a matrix (in this caseR) by the summation method where R is a square matrix with symbolic ...
2
votes
1answer
93 views

Simple-looking Minimize takes for ever

Consider the following: Minimize[{(ξ - x)^2 + (η - y)^2, a ξ + b η == c}, {ξ, η}, Reals] After asking Mathematica to do this yesterday afternoon and forgetting ...
0
votes
1answer
94 views

Animating a Large Graphic Aborts, but Dynamic Works Fine

I'm trying to animate a large Graphics output, and it is returning $Aborted. I'm confused because when I use Dynamic and Slider, the graphics output is exactly what I want, i.e., I can 'animate' the ...
0
votes
0answers
122 views

Run out of memory. How to optimize this code?

I have two sets of data: short with 22 entries, long with 46 entries. I want to take 20 entries from ...
1
vote
1answer
68 views

Performance problem with summation in Mathematica

I was trying to find out why the following function is rather slow. ...
0
votes
0answers
60 views

Improve performance of processing transactions in a large file

I want to work with a table which has 296,705 transactionslines and 172,147 transactions. ...
2
votes
3answers
138 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
votes
1answer
155 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 ...
10
votes
5answers
1k views

Generating an Ulam spiral

An Ulam Spiral is quite an interesting construction, revealing unexpected features in the distribution of primes. Here is a related topic with one answer by Pinguin Dirk, who has provided one ...
1
vote
1answer
52 views

Let's do this list-rearrangement prettier [duplicate]

Suppose that i have a list in this format= $list=\{ \{a,obj1 \} ,\{c,obj2 \}, \{a,obj3 \}, \{b,obj4 \} \dots\}$ I want to construct a new list in this way: $ newlist= \{ \{ \{a,obj1\} , \{a,obj3\} ...
0
votes
0answers
165 views

Is there a way to give Mathematica extra memory?

I am running Mathematica 10 (Student Edition) on Mac OS X 10.7.5 on an old Mac Pro. I have lots of extra RAM that the system isn't touching, and I would like to give some of it to Mathematica in the ...
5
votes
1answer
137 views

Slow-down encountered when using NMinimize with a compiled function

I'm minimizing a large function. Evaluating the function is very slow symbolically but using Compile I can get ~100x speed-up on this step. However, despite this, the NMinimize process is only ...
3
votes
1answer
105 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 ...
11
votes
2answers
262 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 ...
6
votes
1answer
1k views

MathKernel.exe capped to use only 13% of CPU?

I am using a Windows machine with 8 cores. No other process than Mathematica 8 is using CPU time right now - still the MathKernel.exe CPU usage does not go beyond 13%. My current computation takes ...
0
votes
0answers
153 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 ...
20
votes
6answers
2k views
13
votes
3answers
1k views

Can Mathematica's random number generation be improved?

Performance on Random Number generation is intolerable. Whenever you need many deviates from the same distribution but with different parameters it takes forever. Here is a thread on Poisson ...
0
votes
1answer
60 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 ...
12
votes
1answer
230 views

The efficiency compare between Flatten[#, 1] & and Join @@ # &

Err..Often I met the situation to join lists at the first level and I used to just Flatten[#, 1] &@ them. However, I found(when glance over the mathematica.stackexchange.com) someone else prefer ...
3
votes
2answers
70 views

Slow application of `Outer` on a matrix

I have some performance issue with the calculation of a gaussian kernel applied to a not-that-large dataset. I'm not very good with performance tuning in Mma and I have the feeling this one could be ...
0
votes
0answers
33 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. ...
3
votes
2answers
73 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 ...
38
votes
2answers
2k views

Benchmarking Mathematica performance on the Raspberry Pi

It is not surprising that Mathematica on the Raspberry Pi is slow and clunky. In Stephen Wolfram's words, the command line is "quite zippy" but the notebook interface is "a trifle sluggish by modern ...
11
votes
1answer
302 views

Does NRoots own an abstract counterpart? If not, can we write one?

We know when solving linear algebra equations, despite its abstract syntax, LinearSolve is much faster compared to Solve: ...
7
votes
2answers
1k views

Dramatic speed difference of code on Matlab and Mathematica

Background: I was trying to convert a Matlab code (fluid simulation, SPH method) into a Mathematica one, but the speed difference is huge. Matlab code: ...
1
vote
1answer
66 views
2
votes
1answer
108 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 ...
1
vote
2answers
88 views

Performance in calculating maximum-likelihood- based estimates

My probability density function is a complicated one for which numerical estimation is necessary. Here my pdf: ...
4
votes
2answers
195 views

How can I speed up my compiled RBF interpolating function?

Overview I have a function that acts like the Interpolation on sparse $n$-dimensional data using a simple implementation of RBF interpolation method. I want my ...
0
votes
0answers
49 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 ...
3
votes
2answers
86 views

Most efficient way of splitting a file into length-prefixed blocks

Let's say I have a really big file (>100MB) that consists of length-prefixed blocks, i.e. the first byte of each byte block indicates the length of the rest of the block. This is a simplified example ...
2
votes
0answers
95 views

How to efficiently find parts of a string with beginning and ending specified?

I'm trying to find specific URL addresses from a html document. The addresses can be found between the strings "href=\"" and "\" class=\"listing". The problem is not including strings like this: ...
6
votes
0answers
112 views

Slow NIntegrate over complicated domains (sometimes)

This is no longer a problem with Mathematica 10.* where I can use regions to do the integrations Overview I have a very large matrix I need to calculate where each element requires the integration ...
9
votes
1answer
147 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 ...
6
votes
2answers
191 views

Efficient Lloyd Sampling of Images

I want to sample a grayscale image so that every voronoi cell contains approximately the same total intensity using lloyd sampling. My current code is kind of slow and I was hoping for some advice to ...
9
votes
3answers
404 views

Slow work of SQLInsert with SQLite

I want to store my data in SQLite database, but writing large numbers of data its too slow. For example: ...
5
votes
1answer
259 views

Function takes hugely different times to evaluate on sets of virtually (but also literally) identical data

I'm experiencing something which I believe to be weird with a function that I wrote. Briefly: what happens is that I generate random data to feed my function in two different but equivalent ways ...
8
votes
0answers
109 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 ...
3
votes
3answers
284 views

fastest way to perform the following summation

I have a vector $A$ with components $A_{i}$, and two matrices $X$ and $Y$ with components $X_{ij}$, and $Y_{ij}$ respectively. What is the fastest way of performing the following summation ...
2
votes
3answers
88 views

Efficiently plotting a function with its translates?

How does one efficiently produce a plot of {f[x], f[x]+1}? Assume that f[x] is a long computation, which I would like to avoid ...
1
vote
1answer
58 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 ...
4
votes
1answer
275 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: ...
1
vote
1answer
121 views

How to rewrite a nested loop with Reap and Sow [closed]

I was wondering if anyone know how to rewrite the following nested loop but using Reap and Sow. I need to reduce the execution time. Thank you. ...