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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1
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1answer
58 views

Apply NonlinearModelFit to an image

I have several images (in FITS format), which I want to fit with a 2D-Gaussian distribution. The problem is that NonlinearModelFit expects data in the form of a ...
6
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0answers
59 views

Using a Mathematica index as a DiscreteVariable in NDSolve when solving a coupled set of ordinary differential equations

Context Since the explanation below of the problem to be solved is lengthy, let me preamble this by saying that I have code that works to solve the problem, but I don't know whether (1) it's ...
8
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2answers
208 views

How to read off coefficients of tensor-like expression in a speedy way?

I am considering identities involving t[a, b, c, d, ...], where number of indices is fixed. t has the cyclic property so that ...
4
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1answer
75 views

Reap, Sow with Parallelize: bad performance, why?

I have a question about the performance of Reap and Sow with Parallelize. I am aware of the following questions How to collect result continuously (interruptible calculation) when running parallel ...
3
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0answers
46 views

How to perform Bayesian optimization with Mathematica?

Does Mathematica have any Bayesian optimization methods for learning hyper-parameters? Practical Bayesian Optimization of Machine Learning Algorithms Jasper Snoek, Hugo Larochelle and Ryan P. ...
0
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0answers
27 views

Manipulate function as a form of human input [on hold]

I need to streamline a program where one of the lines is essentially Manipulate[f[dataset[a]], {a, min, max}]. I need ...
5
votes
1answer
102 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 ...
6
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3answers
149 views

Speed up derivative evaluation

I'm trying to calculate the normal vectors and the tangent vectors at the discrete points of a suface. For example: ...
16
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1answer
415 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 ...
6
votes
1answer
316 views

Speeding up the non-negativity algorithm for multilinear function with interval probabilities?

The algorithm is a branch-and-bound algorithm that calculates the non-negativity of a multilinear function with interval probabilities. The lines 9-11 has an optimization that is explained on the ...
4
votes
2answers
227 views

Why does having many Print statements slow down my code?

I have a code that I need to debug. I have put a Print[] into it that should give about 10^4 prints for table entries. I know that 10^4 is large, and this exposes ...
1
vote
1answer
122 views

Making ReplaceAll faster

I have a list of functions ncalc that is calculated by ...
10
votes
1answer
275 views

Drop selection of columns from a ragged array

I have an application where I need to drop some arbitrary list of columns from a ragged array (where of course the shortest array rows have at least all the specified columns). E.g., given a ragged ...
5
votes
1answer
147 views

Force Dispatch to generate dispatch tables

Dispatch creates hash tables only for lists of length larger than 3. Is there any way to force MMA to create hash tables even for lists of length smaller than 4? ...
16
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0answers
212 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
0answers
45 views

Fast construction and reshaping of large tensors

I'm trying to construct a large matrix which is derived from some higher rank tensor (the rank of interest to me changes case by case, so it needs to be a general method). Currently, the process of ...
11
votes
2answers
417 views

How to speed up Colorize

I have a list of about 500 images similar to the following: A = Import["http://i.stack.imgur.com/1bV4O.png"] ...
7
votes
2answers
307 views

Using a given colour table with Image?

Context I would like to represent large images with a given colour table. Now, if I use Image ...
14
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1answer
188 views

Major slowdown when using a ColorFunction with more than one named scheme

Problem remains in 10.1 Earlier Kuba noted a major slowdown with code Simon Woods posted. Here is a simplified example. First a color function using two different named gradient schemes: ...
1
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0answers
57 views

Optimizing orthogonal nonlinear regression code

I'm doing a simulation problem on the Langmuir adsorption model, where I need to obtain the model parameters from simulated data using the orthogonal nonlinear least-squares regression method. Here is ...
8
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1answer
198 views

Why is `Block` significantly faster than `ReplaceAll` for inputting variable values

Given that the documentation for FindMinimum uses ReplaceAll for its various examples of what to do with the found solution to ...
23
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0answers
361 views

What Mathematica features and idioms have $n^2$ complexity or worse

Here are a few: AppendTo[data, elem], Sort[data, test], in some cases use of ___ (as ...
4
votes
1answer
73 views

How to create fast functions based on units?

Using units is a good means for rapidly developing code, since it provides some error control. Hovewer, using Mathamatica functions containing units appears to be copmutationally inefficient. ...
10
votes
6answers
530 views

How to find all the positions of max value of a list efficiently?

For Example, list=RandomInteger[{1,100},2000]. Yes,I know Position[list,Max[list]] can do. But it's based on pattern ...
0
votes
0answers
71 views

NIntegrate gives message NIntegrate::vars:

As seen in the code below, I initially constructed a list of functions of two variables ζ and t0. These functions are pure ...
1
vote
0answers
54 views

Orthogonality relations of Hermite polynomials

The Hermite polynomials are orthogonal. $$ \int_{-\infty}^\infty H_m(x) H_n(x) e^{-x^2}\, \mathrm{d}x = \sqrt{ \pi} 2^n n! \delta_{nm} $$ Does Mathematica not use this relationship? Because running ...
11
votes
2answers
182 views

Faster trimming of leading/trailing zeroes in rectangular array

Given a (large) rectangular array, e.g. (small for example case): ...
8
votes
3answers
401 views

Benchmarking expressions

It often happens that I'd like to know which of two or more alternative expressions (that should evaluate to the same value) is fastest. For example, below are three ways to define a function: ...
12
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0answers
169 views

Performance problems in new Sequence functions

The new-in-10.1 Sequence* family of functions should provide newly optimized methods for handling sequence problems. Happily in some cases they do! For example ...
4
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2answers
44 views

NaNs in tabular data and import performance

I'm working with some data files that are just too large for Import. I tried using ReadList, specifying either ...
3
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1answer
114 views

Constructing lists in an efficient way

I have a list of functions and I want to separate them into two lists: a list that contains the functions that have at least one zero and a list that contains the functions that do not have ...
0
votes
1answer
53 views

Returning functions that are partly evaluated

I have some performance issues when calling Table[{h, Slow1[h, n]}, {n, nlist}, {h, 0.1, 10, 0.5}]; for a given list ...
0
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0answers
37 views

What is the right way to remove head of a number? [duplicate]

I often have a number for which I want to remove its head, e.g. {1}. I know of two ways to remove the head: {1}[[1]] # & @@ {1} Neither of these methods seem ...
1
vote
1answer
72 views

Slow program- Mathematica shuts down

I've been trying to draw dynamic pictures of level sets of certain polynomials. The code right now looks like that : ...
5
votes
2answers
144 views

Combinatorics: Placed errors

Consider a vector of length n where each element can take one of the values U, X, ...
7
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1answer
137 views

Compiled function crashes kernel when trying to list over different length arguments

I'm trying to speed up a tally/binning operation that I have to run many times. I have many lists of between 1 and 10 numbers from the range [1,5] and I want to ...
4
votes
1answer
67 views

Speed up the auxiliary function magicSquare when $n$ is doubly-even

Today, I saw a question about magic square. Please see here When $n$ is doubly-even.Namely, Mod[n,4]==0 ...
0
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0answers
23 views

Timing of an Evaluation is not correctly displayed

From: http://reference.wolfram.com/language/howto/DisplayTheTimingOfAnEvaluationInANotebookWindow.html I ran a process that took about two minutes to finish. But the time recorded is only 0.18 ...
26
votes
1answer
853 views

Fast Spherical Harmonics radiative transfer

This is a rather specific question and I apologize for spamming you with some lengthy code. But it could be interesting for some reader and maybe you can help out, so please bear with me. I am using ...
2
votes
1answer
68 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. ...
2
votes
2answers
135 views

NIntegrate over a list of functions

This question is the result of these other two questions. Question 1 and 2. I thought it would be better to ask a new question rather than deleting previous one. I think When ...
0
votes
2answers
84 views

Is it possible to sum the results of a Map - Apply?

I am fairly new to functional programming and would like to replace a For[] loop that sums the results over a Dataset. This may be a bit different since the ...
6
votes
1answer
183 views

Speed up MinimalPolynomial

My Mathematica code runs slowly MinimalPolynomial[Sqrt[2] + Sqrt[3]+ Sqrt[5]+ Sqrt[7]+ Sqrt[11]+ Sqrt[13], x] runs slowly, but the Maple version ...
2
votes
1answer
94 views

Efficient way to perform local Otsu thresholding on image

I have images of cell nuclei that have locally varying intensity distributions. Therefore, I need a robust local threshold algorithm. LocalAdaptiveBinarize works ...
31
votes
5answers
2k views

How to efficiently find positions of duplicates?

Is there an efficient way to find the positions of the duplicates in a list? I would like the positions grouped according to duplicated elements. For instance, given ...
8
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2answers
141 views

why MeanFilter is nearly 100 times slower than MovingAverage for 1D array?

I used to average over my data with MeanFilter before I learn about MovingAverage and thought that these two functions are similar except that MeanFilter is more powerful for its ability to deal with ...