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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2
votes
1answer
153 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
101 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
77 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: ...
1
vote
0answers
132 views

Autocorrelation of 3D Points

I'm trying to compute the autocorrelation of a list of points $(x,y,z)$ in 3D. Can the CorrelationFunction or maybe ...
2
votes
0answers
101 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: ...
11
votes
1answer
296 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 ...
7
votes
2answers
229 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
273 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
349 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: ...
4
votes
4answers
466 views

Creating a fast random array generator

I want to create N x N array of random numbers. (N is an integer). The constraints are, each element should be between 0 to l(integer) ( here 0<= l <= N) and the sum of elements in each row ...
2
votes
3answers
94 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
303 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 ...
1
vote
1answer
63 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
votes
0answers
98 views

Applying the square root of operator on polynomial functions

I am trying to apply an "operation" on polynomial functions: apply the operator $(\frac{\partial f}{\partial x}-y\frac{\partial f}{\partial z})^2+(\frac{\partial f}{\partial y}+x\frac{\partial ...
0
votes
0answers
124 views

Random generation of three-non-collinear and four-non-coplanar points in 3D space

Please, take a look to this code. How it can be improved so that the time execution becomes smaller? ...
3
votes
1answer
41 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
207 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. ...
13
votes
2answers
376 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
84 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. ...
2
votes
1answer
613 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 ...
9
votes
3answers
394 views

Generalization to AllTrue, AnyTrue and NoneTrue

I am wondering if there is a natural Mathematica way to generalize those functions. To be specific, All three functions AllTrue, ...
4
votes
5answers
321 views

Check whether array has only constant entries?

I have an array arr with n entries. Now I want to check whether ...
1
vote
0answers
56 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
136 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
200 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 ...
16
votes
2answers
454 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: ...
2
votes
1answer
160 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
votes
2answers
324 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
320 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 ...
8
votes
2answers
231 views

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

I have this code that is originally 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
3answers
254 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 ...
1
vote
0answers
135 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
465 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
270 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). ...
13
votes
3answers
489 views

Collatz optimization

I'm VERY new to Mathematica programming (and by new I mean two days), and was solving Project Euler question 12, which states: Which starting number, under one million, produces the longest ...
11
votes
2answers
725 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 ...
5
votes
1answer
172 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
105 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
378 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 ...
6
votes
1answer
134 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
votes
1answer
137 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
233 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: ...
4
votes
1answer
113 views

How do I understand this big difference in speed:

A friend of mine found a huge difference in runtime speed between these two ...
0
votes
1answer
70 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
131 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 ...
4
votes
1answer
342 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: ...
4
votes
1answer
129 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
2answers
360 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 ...
3
votes
3answers
142 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: ...