# Tagged Questions

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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### How to increase speed of iterations with nonlinear functions

Let me ask about part of a problem which I have in solving of a nonlinear DE (numerically). I am working with vectors of length $xN$. I have an initial vector $v$, a given $xN\times xN$ matrix $A$ and ...
2answers
212 views

### Speeding up generation of block diagonal matrix

I'm struggling with the following problem. I have $48$ square matrices (full, filled with real machine precision numbers, thus are packed, all different) of size $128$. I wolud like to place them on a ...
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87 views

### Deleting isomorphic graphs efficiently

I'm trying to delete isomorphic graphs from a large list. My solution is as follows: DeleteIsoG1[gl_List]:= Module[{}, DeleteDuplicates[gl,IsomorphicGraphQ]]; ...
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852 views

### Terrifying performance decrease for contour/density plots in v10.1 -> 10.3

Bug introduced in 10.3 and fixed in 10.3.1 I setup for download a test dataset at http://www.inrim.it/~magni/cm.dat.gz (a set of 64800 triplets x,y,z). The behavior can be reproduced with the ...
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### Count degrees of freedom of a polynomial

I want to count the independent degrees of freedom of a polynomial in three variables $(z_0,z_1,z_2)$. Therefore I take the coefficients of $f$ and compute the rank Jacobian with respect to the ...
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109 views

### Manipulate gets stuck when ConvexHullMesh is made transparent

Version 10.3 The followinng Manipulate is a bit slow, but quite OK ...
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### precision and speed inefficiency issues of Nearest function with sqrt expression [closed]

Recently, Nearest has been attacked for many bugs. Some are already fixed. I am going to show some issues when Nearest applied ...
2answers
147 views

### How to be more efficient/faster with this MatrixExp-vector multiplication?

I am looking for expertise that helps to improve speed of the code below. First, a little bit of background: There is some system of differential equations $\dot{\vec{m}}(t)=S(t)\vec{m}(t)$. In order ...
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343 views

### Smallest element distance between two lists

I have a problem, where I generate two lists of points, and I want to see which points are the closest. If I just want to find which ones are exactly the same, I can use ...
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### MySQL insert statement over remote server is extremely slow. How can I speed it up?

I need to insert values to a remote MySQL server. However it is extremely slow compared to a local MySQL server. This is my timing for the local MySQL server ...
2answers
160 views

### Efficient and fastest way to execute 4 nested loops

I have a question regarding the use of ParallelDo. I tried to parallelize the following code involving four nested Do loops by ...
2answers
215 views

### Speeding up code for lattice generation

Below is a lattice point generation code I write ...
1answer
97 views

### Expensive MeshRefinementFunction

I want to discretize a region using DiscretizeRegion. Now, I want the mesh to be more refined, when the curvature of a certain function ...
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62 views

### Can not understand this timing result

I set a=1. tmptmp = Tuples[Range /@ {1000, 100}].{{3 a, 0}, {0, Sqrt[3] a}} And then run ...
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### NMinimize error

I want to use NMinimize in the following way: ...
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### Long delays before showing the result in a notebook

I'm new to Mathematica. I have Version 10.3.0 running under Windows 10, 64-bit. If I open the 10.3.0 kernel and type 2 + 2 Shift Return I get an immediate answer. If I open the main program and ...
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128 views

### Speed matrix multiplications

I am trying to run this function ...
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182 views

### Exceeding time constraint of 300 seconds when taking coefficients of some expressions from schur polynomial [closed]

I have written a code that takes coefficients of some expressions from schur function, but it seems to take a lot of time, and Mathematica will stop after 300 seconds saying that it's over the time ...
1answer
89 views

### Efficiently traversing a list

Suppose I have a large list of algebraic expressions, sorted by their equivalent numerical value (under a certain set of assumptions). Some of these expressions are identical, but commands like ...
4answers
202 views

### Timing problem with ReplaceRepeated

I have the following data: ...
2answers
108 views

### Parallel function evaluation for minimal value

I am asking myself, if the evaluation of a function f looking for a minimal value over a discrete set of values can be parallelize (brute scan for a potential ...
1answer
85 views

### Why does Timing return different times for the same calculation?

I did an experiment in which I calculated the same quantity two different ways to see which method was faster. To my surprise, the kernel time was different in different runs. In fact, which method ...
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124 views

### Efficiently generating plots from lists of differing lengths

I guess this is more of an informatic question. A quite complicated function of mine generates me a list of valid points, depending on a parameter, like this: ...