Questions about optimizing code for faster results, or how to do faster computations.

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3
votes
2answers
113 views

Time-efficient manipulation (zeroing) of expression

I have huge matrices in the form of ...
2
votes
1answer
133 views

How can I reduce computation time while still obtaining a good approximation for my function?

I am new to any CAS (and Mathematica, for that matter) and new to StackExchange too, so forgive me and correct me on any mistakes. I have this function: $J_p=\sum_{m,n=1}^{\infty} ...
22
votes
2answers
464 views

Why is Query so much slower than Part?

Time for another of these(1),(2) as yet another new-in-10 function appears to have poor performance compared to older alternatives. This time: Query appears to be ...
3
votes
1answer
137 views

Why is my compiled code slower?

I am trying to make a Mathematica program run faster. Here is part of the original version. It takes as input the integers X (of order 100), J (of order 10000), and n (of order 100), the real number p ...
15
votes
1answer
369 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 ...
7
votes
1answer
190 views

Is there a faster way to Map an Association?

Consider mapping an existing Association in a manner such as this: ...
8
votes
4answers
342 views

Fast method to select matrix elements based on a vector of positions

There is an operation for which I have long wanted to find a better solution. Let: a be a matrix of dimensions $m\times n$ ...
7
votes
1answer
256 views

Porting code from MATLAB

I'd like to switch from MATLAB to Mathematica for my research in digital signal processing. I used Mathematica a lot during the '90s but I haven't used it since then, so I might as well be a complete ...
2
votes
0answers
105 views

Mathlink program with low cpu usage on linux machines only

Question I am incorporating some c++ code via Mathlink into my simulations in Mathematica. My questions involves the execution efficiency of the c++ code on different machines. For example, on my ...
6
votes
1answer
184 views

Why is AllTrue much slower than VectorQ?

This seems to be a theme with V10, a new function dedicated to a specific task doesn't live up to expectation performance-wise. Mr. Wizard has already uncovered 2 such functions here and here. So how ...
20
votes
3answers
742 views

DeleteDuplicatesBy is not performing as I'd hoped. Am I missing something?

Déjà vu: a new-in-v10 function should provide a better solution to an old problem, but my enthusiasm is curbed when I run timings. This time the function is ...
34
votes
2answers
852 views

Why is the new PositionIndex horribly slow?

This issue has largely been mitigated in 10.0.1. New timings for the final test below are: ...
0
votes
0answers
94 views

Timing: how make a program to work faster using built in functions and tables

I want to improve my code to make it working faster even for very large numbers. ...
5
votes
0answers
218 views

Problems extending NelderMeadMinimize into 2D

Update The eventual route I followed was to adapt a version of the NM-simplex written in C and link to it with MathLink. Once I've tested this out fully I'll post it here. I've been playing around ...
0
votes
1answer
91 views

How can I speed up this multi-equation Solve problem?

I'm trying to solve a set of equations (chemical kinetics for a complex system, but don't worry about that). I ran it for 24 hours and I got no output. Here is the relatively simple code (I want to ...
0
votes
0answers
29 views

Speed up series expansion [duplicate]

I have a rather complicated function that I need to expand it in series, which is quite straightforward but takes a long time. I was wondering if there is a way to speed up such a calculation: ...
-3
votes
1answer
89 views

Why does the function Evaluate speed up one function by orders of magnitude and another function not at all?

I've got two functions, one sample function (function 1) i've created for demonstartion purposes here, and my actual function. The function Evaluate speeds up the sample function by orders of ...
0
votes
1answer
116 views

Why does Evaluate fail? [closed]

If i use this code: ...
1
vote
0answers
44 views

Understanding Mathematica: How to write fast code? [duplicate]

I'm relatively new to Mathematica but have done a few projects using it so I'm quite comfortable with the syntax and the basic functions available. Since I've had programming experience in the past I ...
3
votes
2answers
309 views

How to speed up minimization of function

I have the fallowing code (the functions within that code are replaced by simpler ones, but the code structure is identical): $$$$ ...
1
vote
0answers
93 views

Speeding up the numerical integration of a certain function

I'm using the following function f[t_] := 3/4 t^-3 NIntegrate[(x^4*Csch[x/2]^2), {x, 0, t}, Method -> {Automatic, "SymbolicProcessing" -> 0}]; I ...
0
votes
0answers
77 views

Timing Differences

In More efficient implementation for comparing coefficient lists in a Do-loop link, george2079 posts in his first answer a piece of code that takes 352 seconds to compute. When I run this same piece ...
1
vote
2answers
197 views

More efficient implementation for comparing coefficient lists in a Do-loop

I'm wondering how to speed up the following code so it actually computes for $n=2$: ...
8
votes
5answers
812 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 ...
7
votes
3answers
431 views

Speed up ContourPlot3D

I have two issues with the following code. (1) It executes too slowly. If I use "Speed" instead of "Quality" for PerformanceGoal, I get the speed but an undesirable delay in proper rendering of the ...
2
votes
4answers
175 views

Replacing High Densities of 1.s in Very Large Binary Arrays

I am working with very large binary arrays on the order of {100,100000}. It may look something like this. ...
10
votes
0answers
123 views

Exp is slower for some number ranges

I get a hit on performance with the Exp function depending on the range of my inputs. for example, with: ...
3
votes
0answers
177 views

Module in numerical model for NonlinearModelFit is slow and leaks memory

I am trying to make a NonlinearModelFit where the model is the result of a numerical calculation. My code works, but it is very slow and also seems to have a memory ...
1
vote
1answer
147 views

Speeding up a function

This is un updated version of a previous (now deleted) post of mine. I need to marginalize a distribution. I was suggested to use the code in this thread. This works just fine, but the problem is ...
3
votes
1answer
278 views

How to efficiently drag points on a curve within a Manipulate

My intention is to demonstrate on any conic various metrics properties on points belonging to the conic and connected by lines. I want the points to be dynamically moved not the usual way, ...
5
votes
3answers
233 views

Split list of states by run lengths and discontinuous changes in state

I was asked to look into writing some simulation code for a user, where the simulation output (x) would oscillate between three possible states: ...
0
votes
0answers
88 views

How to save the results in an identical Excel file (.xls) in each iteration of a Do loop

Assume the following code (Below code is just an example to clearly illustrate my problem): ...
6
votes
1answer
123 views

Garbage collection for memoized functions on subkernels

I have a top-level function which operates on some data: findBestIntegers[data_]:=ParallelMap[optimize,data] which makes parallelized calls to an optimization ...
15
votes
2answers
393 views

Is there a better way to add elements to a Graphics expression repeatedly?

Consider simple example where a set of points is generated and some are displayed. ...
3
votes
1answer
212 views

Surface area of intersecting spheres

Given a sphere of radius 1 centered at the origin and $n$ spheres with radii $r_i$ centered at predefined coordinates, $c_i$, in space, I am after the surface area of the unit sphere that is not ...
5
votes
1answer
534 views

Bresenham's line algorithm

Bresenham's line algorithm is producing discretized line for given two points for purpose of plotting for example. Like that: I have to stress that I'm interested in positions, not a plot. ...
3
votes
2answers
250 views

DynamicModule/Dynamic CheckboxBar Slow for Large Lists

I am trying to create a dynamic construct that takes a large list of expressions and allows the user to interactively select any number of entries for further manipulation. This is what I have ...
0
votes
0answers
155 views

Speeding up inversion of symbolic matrices by invoking caching

Is it possible to reduce the computation time taken to find inverse of symbolic matrices USING CACHING TECHNIQUES accessible (if any)? I am trying to compute inverse of symbolic matrices of size ...
0
votes
0answers
66 views

Is there a faster way to do Normal[SparseArray[{{1,1,1}→1.2, {1,1,2}→20.2, …, {m,n,p}→0.3}]]?

I have a list of the form {{1,1,1}→1.2, {1,1,2}→20.2, ..., {m,n,p}→0.3} and I want to create an $m \times n \times p$ array, $A$, where the value of $A[[i,j,k]]$ is ...
9
votes
5answers
630 views

Fast way of finding position of Interval containing an Integer

I have a large list (about 2.2 million) of pairs of integers. Each pair defines an Interval[{}]. Given some integer x, I need to ...
1
vote
1answer
137 views

Simulation code performance tuning

The following simulation takes over 20 seconds for evaluation. I have difficulty re-coding it with Nest and Map or Compile functions to make it more efficient. Can some one help with this? The ...
7
votes
4answers
528 views

Suppress connection to Wolfram|Alpha when making unit conversions

I want to speed up calculations with unit conversions. I suspect primarily that some units evaluate from Wolfram|Alpha. Any way to prevent this automatically, so that Mathematica throws ...
4
votes
3answers
516 views

Why is my solution to PE #5 so slow

I'm new to Mathematica and it was suggested to me to go through the Project Euler problems in order to learn it. However, I can't quite figure out why my solution to #5 is so slow. The problem: ...
1
vote
0answers
92 views

Increase optimization processing speed

As you know, sometimes numerically solving of optimization problems takes several minutes. For this reason 2 question came up to me: 1 - When one is abort the optimization procedure, how it is ...
0
votes
0answers
77 views

Speeding up Integrate and the numerical solution

I want to compute the drag of a plate Below is the code I am using to integrate the function ...
0
votes
1answer
109 views

How I can control the speed with which the cone is filled? [closed]

My idea is: By calculating the speed ie VelVol = v2 * t; where v2 is the volume of the second cone (the amount of "water" that is inserted into the cone) You can see that I have 4 slider (The first ...
0
votes
0answers
38 views

Faster evaluation of an expression for brute force optimization [duplicate]

I'm trying to bruteforce an optimization problem and I want to generate roughly a million function evaluations. I was wondering what would be the best for me to do in terms of having the expressions ...
5
votes
2answers
176 views

How does the speed of WriteString compare to other languages?

I'm doing something where the most sensible approach seems to be to open a file and write to it as I process data from some large tables. Old school. While testing the program, I remembered the low ...
11
votes
3answers
2k views

Speed up ordering digit code?

My goal is given an integer number to deduce if its digits increase (or remain the same) from left to right or not. Example: $1236, 123336$ are both considered numbers with increasing digits, but ...
0
votes
0answers
147 views

Code performance problem

Could anyone help me with the attached code? How would you speed up my attached code in some degree? Your comments are highly welcome. ...