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.
3
votes
3answers
87 views
Remove linear trend from data
I have a large data set with 150k lines and two data columns. I noticed that there is a linear trend, which I want to remove. So, I do the following:
first fit with a linear model
...
1
vote
2answers
134 views
Improving speed of Exp[]
I'm working on some pretty intense computation in Mathematica; when my code started running slowly, I tracked the source of the problem to Exp[]. I need to ...
3
votes
1answer
103 views
Why is this code in functional style is slower than procedural style?
I know that in Mathematica a functional programming style is often more efficient than procedural style programming using For loops. But the code shown below seems ...
4
votes
0answers
98 views
Parallelizing is much slower than single kernel evaluation?
Starting with a vector of matrices, tVec, I would like to parallelize the multiplication of each element with the same matrix ...
1
vote
1answer
86 views
how to reduce the time to calculate triple integral
i want to evaluate the following integral, but it takes 15 min to do it. i must reduce the time to calculate it, i have to do a table and create a graph, but takes too long.
anyone have an idea ?
...
6
votes
2answers
109 views
How can this AbsoluteTime call be made faster?
I need to convert tons of date strings into absolute times. This generates an example data set of 10,000 strings:
...
5
votes
0answers
74 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 ...
1
vote
0answers
49 views
Significant platform-dependent efficiency when importing data?
I'm curious, as I understand that answer this way:
If you are using a Linux derivative or something like cygwin on
Windows, then this is an efficient solution for reading only the third
field ...
4
votes
2answers
68 views
Efficient drawing of convex polyhedron given a set of points [duplicate]
I have a set of points in the 3D space and I want to draw the bounding convex polyhedron of those points. A very naïve solution would be to draw a triangle between every three points:
...
2
votes
2answers
88 views
Importing several huge files with headers & footers
having here several files in ASCII format
http://ge.tt/91rv0Jf/v/0
I want to import, while removing headers and footers and then join the several lists.
...
13
votes
3answers
322 views
Select performance
I am fairly new to mathematica and working my way thru Paul Wellins book on Mathematica programming so experimenting with various language constructs. I was experimenting with ...
2
votes
1answer
85 views
How can I place gui controls inside Grid? [duplicate]
In all my apps, I am facing a problem about placing the Gui controls inside Grid.
For this purpose, I wrote three functions.
The first function, ...
0
votes
2answers
124 views
Fast Autocorrelation Computation
I want to compute the Autocorrelation Function (ACF) of a data table with $10^6$ entries. I know that there is a built-in function in Mathematica for that, but because I do not know how exactly it is ...
0
votes
0answers
80 views
Speeding up a for loop by removing a Sum command
I am attempting to create an array that has of order 1000 x 1000 entries. In the entry of the last column of each row, I have to carry out a sum that could contains 100s of terms (I only used 40 here ...
10
votes
4answers
279 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 ...
2
votes
0answers
103 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 ...
5
votes
1answer
260 views
Montgomery Modular Exponentiation
I'm trying to write a Montgomery exponentiation based on this which can compete with Mathematica PowerMod. We know that PowerMod ...
13
votes
1answer
238 views
Optimizing a Numerical Laplace Equation Solver
Laplace's Equation is an equation on a scalar in which, given the value of the scalar on the boundaries (the boundary conditions), one can determine the value of the scalar at any point in the region ...
13
votes
2answers
281 views
Fastest way to measure Hamming distance of integers
I am looking for a fast and robust way to calculate the Hamming distance of integers. The Hamming distance of two integers is the number of matching bits in their binary representations. I expect that ...
1
vote
2answers
149 views
What ways are there to convert an Integer to a list of digits?
How can I convert an Integer to list of numbers? For example:
781049 ==> {7, 8, 1, 0, 4, 9}
What are the possible ways of ...
4
votes
0answers
94 views
Speeding up multilinear PRA branch-and-bound algorithm with worst-case exponential time scenario with respect to basic events
The algorithm is a branch-and-bound algorithm that calculates dominances for PRA, probalistic risk assessment. The task was to find faster ways to do it in numerical software such as Matlab but we ...
1
vote
1answer
168 views
-1
votes
1answer
60 views
Integral evaluation taking too long [closed]
When I try to evaluate the following integral, it runs for a much longer time than I think is should without producing a result. What might be the problem? Can anybody please point it out?
...
7
votes
1answer
141 views
Efficiently filling area with disks located at certain points
Starting from a set of points, I want to fill an area using disks. Each disk's center should be one of the points and the disks should not overlap. I've managed to write a function that, given a list ...
4
votes
2answers
119 views
Speed up plot of $\sum_{j\ge1} 2^{-j}(1-2^{-j})^{n-1}$
I'm a beginner at Mathematica. I would like to plot the following function:
$${n\over2} \sum_{j\ge1} 2^{-j}(1-2^{-j})^{n-1}$$
However the following code is just too slow:
...
1
vote
2answers
87 views
Speeding up a simple simulation with random extractions
I wonder if anybody can help, I need a hand with a simple simulation I am writing with Mathematica (I am using version 8). Basically it creates a list (called l) with numbers from 1 to n and a random ...
0
votes
0answers
80 views
Speeding up numerical computations
So, after seeing this and this post, I was thinking whether there were any general rules for speeding up numerical computations (not only NIntegrate or ...
2
votes
0answers
96 views
Is there documentation on the comparative performance of Mathematica functions?
Recently I have been solving some Project Euler problems. I find there are always several ways to do the same thing. For example, one could join two lists like this:
...
5
votes
3answers
152 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:
...
6
votes
4answers
150 views
Why does array packing in Table behave like this?
Consider the following example, which generate two identical arrays. Why sometimes the array is packed and sometimes it doesn't? And why they perform differently?
Here the arrays are packed:
...
5
votes
1answer
120 views
Modular arithmetic - efficiently calculating the remainders of factorials
When working on this question regarding the divisibility of the sum of factorials, I decided to write some code to test "small values" of the problem using the following code.
...
14
votes
4answers
266 views
How to remove duplicates from set of machine precision 2D points?
I have a set of 2D points with machine precision coordinates. I need to remove all duplicates. Performance is important.
This is the most obvious fast solution:
...
12
votes
3answers
448 views
Fastest way to calculate matrix of pairwise distances
It is a very common problem that given a distance function $d(p_1,p_2)$ and a set of points pts, we need to construct a matrix ...
11
votes
5answers
194 views
Faster way to convert triangle list to edge list with no duplicates
I have a list of triangles returned by a Delaunay triangulator, in the following format:
...
10
votes
5answers
488 views
Iterate until condition is met
I want to find the first 5 prime numbers of the form $n^6 + 1091$. I have used this code:
Timing[Select[Table[n^6 + 1091, {n, 10000}], PrimeQ, 5]]
Which gives ...
0
votes
1answer
89 views
PDF on TransformedDistribution of two BinomialDistribution too slow
I'd been doing my own convolutions of distributions for some calculations, decided to use built-ins.
With
...
2
votes
2answers
108 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
...
15
votes
3answers
327 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
...
10
votes
3answers
232 views
Efficient implementation of a linear complexity measure of binary sequences
For a implementation of testing the quality of random number generators I implemented the NIST test suite in Mathematica based on the nice workbook by Ilja Gerhardt.
However I took up the challenge ...
0
votes
0answers
61 views
Complex Integration Optimization
The following code culminates in plots calculated for each value of t as given below.
I have tried compiling one of the functions and adjusting the precision of both the integration and the plotting ...
7
votes
2answers
136 views
Solving variant of the knapsack/money-changing problem
I'm trying to solve a variant of the knapsack/changing money problem where I have a set of a few numbers and I'm trying to find the linear (integer) combinations of them which are close to a given ...
5
votes
1answer
90 views
Does pass-by-value affect the performance of function calls?
I only have a little coding experience in C, and I remember I was told that pass by reference is more efficient than pass by value since the parameters don't need to be copied. Since there is no pass ...
5
votes
2answers
169 views
Variant of the cutting-stock problem in Mathematica
I'm pretty new to Mathematica and am trying to learn to solve problems in a functional way. The problem I was solving was to list the ways in which I could sum elements from a list (with repetitions), ...
6
votes
2answers
200 views
CorrelationFunction for vectors
Mathematica 9 has a new CorrelationFunction. Sadly the joy does not last long, as I can't get it to work with vectors. I would like to make a velocity correlation ...
8
votes
1answer
226 views
Optimizing the performance of an algorithm
First - a bit of an introduction. If you're only interested in the code, you can skip this section.
The following question is drawn from Dennis E. Shasha's Puzzling Adventures, and is listed under ...
2
votes
3answers
134 views
Selecting subsets of a list containing a specific element
I'm trying to generate all the subsets of a set containing a specific element.
For example, for the set {1, 2, 3, 4}, with the specific element I want inside each subset being 4, the required answer ...
2
votes
1answer
93 views
6
votes
2answers
179 views
Fastest way to test if a numerical array has complex elements
I am looking for the fastest way to test whether an n-dimensional numerical (NumericQ) array (in the ArrayQ sense) is complex or ...
9
votes
2answers
195 views
Speed up 4D matrix/array generation
I have to fill a 4D array, whose entries are $\mathrm{sinc}\left[j(a-b)^2+j(c-d)^2-\phi\right]$ for a fixed value of $\phi$ (normally -15) and a fixed value of $j$ (normally about 0.00005). The way ...
0
votes
0answers
106 views
A simple For loop visibly slowing down. Advice to fix?
I have run into a unique problem. I am going to try and describe my code and what is happening as understandably as possible.
I have a For loop that does the same set of calculations over and over ...
