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.

learn more… | top users | synonyms (3)

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
112 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
48 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
116 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
113 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 ...
12
votes
1answer
222 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
67 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 ...
8
votes
0answers
104 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 ...
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 ...
3
votes
2answers
60 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 ...
6
votes
2answers
994 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
57 views

Performance boost for definite integration with symbolic limits

In Mathematica, the symbolic definite integration ...
1
vote
2answers
76 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: ...
2
votes
1answer
85 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 ...
3
votes
2answers
82 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
2answers
63 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: ...
2
votes
0answers
91 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
2answers
172 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 ...
5
votes
1answer
257 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 ...
11
votes
1answer
293 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: ...
2
votes
3answers
85 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 ...
3
votes
3answers
263 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 ...
3
votes
1answer
38 views

Is it possible to generate a message when precision upgrade occur?

I use Mathematica mostly for numerical simulation, so most of the time double precision (or machine precision) is enough for me. Mathematica has this nice feature of automatically upgrade to arbitrary ...
1
vote
1answer
98 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. ...
6
votes
3answers
161 views

How to speed up the plotting of B-spline curve?

Three months ago, I asked a quesion about B-Spline basis function here, Today, I used this function to plot B-spline curve. The definition of $N_{i,p}$ ...
0
votes
0answers
76 views

How to accumulate elements in a list using Reap and Sow [duplicate]

Does anybody know how to rewrite this fragment using Reap and Sow instead of AppendTo. I need to reduce the execution time. Thank you. ...
1
vote
1answer
256 views

How to implement the directed Barabasi-Albert algorithm in Mathematica?

Does anyone know how to implement an efficient version of the [directed Barabasi-Albert algorithm][1] in Mathematica that scales until hundred of thousands nodes? The directed network mechanism is ...
1
vote
0answers
47 views

Complex input for Compile makes it slow

I asked a question here and then tried to use Compile for the solution to gain even more speed. Inside Compile there is a loop ...
3
votes
1answer
107 views

Making table of matrix product and efficiency

I want to make a table in which each element is a matrix product: ...
4
votes
2answers
189 views

Generate lists that satisfy a condition in an efficient way

The following code produces lists of sublists with maximum length 5 that shuffle zeros around an ordered list (here {1,2}). It produces all permutations while ...
15
votes
2answers
403 views

Why is my data 10 times slower than random data when doing matrix multiplication

I have some data generated from some program, and it appears that matrix multiplication on these data are about 10 times slower than on some random data: ...
11
votes
2answers
253 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
1answer
244 views

Lookup construction using data matrix and Reap/Sow versus AppendTo`s

I am a user of MMA9 and made my own kind of Lookup, which is now a standard command in Version 10. In my program there is a section in which by means of a StringReplace[ ]-command containing a lot of ...
4
votes
1answer
96 views

Number of divisors visualized with the QPochhammer function, how improve performance of code?

I have this code that originally is Jeffrey Stopple's code for the Riemann zeta function in the complex plane. Because I discovered yesterday that the number of divisors can be generated with the ...
1
vote
0answers
76 views

Speed up replacement using Rule Dispatch Associtation

I knew that this has asked many times, but I hope there is something more could be done to speed this up. The expression kappa is here. ...
4
votes
1answer
213 views

Fast matrix multiplication in MMA and GPU

Matlab multiplies two 3000by3000 matrix around 0.18s faster than MMA. While for just a few matrix multiplications the speed difference is not important, it becomes crucial when I want to do those ...
10
votes
1answer
218 views

Max element of a list with a custom ordering function

I need a function to find max element of a list according to some custom ordering function, assuming that the function implements a total order (elements being compared might not even be numbers). ...
10
votes
2answers
670 views

Rendering thousands of points

I am trying to render an image with some 120,000 Points. Technically it's just 10,000 points, plus their reflection, plus 5 rotations of both of those sets, but I'm ...
4
votes
1answer
154 views

Ruth-Aaron quadruple challenge

This a computational challenge, to find an efficient algorithm to discover a quadruple $(n,n+1,n+2,n+3)$ with the same sum of prime factors as described in the MO question, "Ruth-Aaron triples, etc." ...
0
votes
1answer
95 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
votes
2answers
290 views

Speed up calculation

First of all thanks to: rm -rf, Mr.Wizard, Simon Woods, Pickett, Piotr Wendykier, Mac, Yves Klett, belisarius, halirutan, bill s, nikie, wxffles, ... Everybody of you helped me (a mathematica ...
2
votes
1answer
99 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
votes
2answers
190 views

Animate skips frames and hard to control speed.

I browsed similar questions related to Animate jerkiness like here, but haven't found the right options to control animation rate while also displaying all frames: ...
0
votes
1answer
69 views

Extend a function to all polynomials ( just 2 variables) when one knows its values on monomials

I need your help to make my code faster. I have a formula for computing a value from any monomial $x^i y^j$, say formular1[i_,j_]:=(Gamma[i]/Gamm[j] ). It is just ...
2
votes
1answer
118 views

How to use slots and patterns to reduce repetitive calculation?

This is kind of complicated... How can we make MMa calculate values of a function before doing multiple pattern or slot substitutions? Answers to similar questions didn't cover the case where the ...
0
votes
0answers
47 views

Order of evaluation when using Solve and Minimize

I have to solve numerically an integral, that ends up being more or less as follows: Solve[f[x]==a*Sum[Sin[x-i]*(f[i]-f[i-1]),{i,1,x}],f[x]] (not actual ...
4
votes
1answer
104 views

Most efficient searching algorithm in a table

I am completely new in Mathematica (and in data analysis in general) and I find it really useful, although I still do not use it properly. I have the following question related to data manipulation: ...
3
votes
3answers
129 views

How to pick the maximum of a list? Improving efficiency

I need to find the element of a list, with the highest weight. Example: ...
1
vote
0answers
136 views

Best way to create symmetric matrices with block structure and additional symmetries of the submatrices

Update: you can now skip the "My attempted solution" part and jump to "My first attempt for improvement" in the end of the question. My question is related to Best way to create symmetric matrices . ...