Questions tagged [software]
Questions about libraries and standalone software designed or well-suited for scientific or numerical calculations.
176
questions
0
votes
0answers
11 views
How to solve nonlinear second order ODE in Matlab? [duplicate]
I am working on simulating a car suspension system using Matlab.
Specifically, I have to derive equation of motion using the Lagrange method and then use ode 45 to solve it. However, while using ...
2
votes
0answers
49 views
Continuum solutions for the Dirac equation in Coulomb potential - numerical codes
Following the representation used in [1, pag. 11] the solution of the Dirac equation in polar coordinates for energy $E$ is of the type:
$$ \psi_{E\kappa m}(\bf{r})= \dfrac{1}{r} \Bigg( \begin{matrix}
...
2
votes
1answer
248 views
Reference request: C++ and numerical analysis book
I'm a master student with a good Numerical analysis background. I'm going to do a master thesis in the same subject, but I need to use C++ since my advisor loves it, and I also believe it's the best ...
1
vote
2answers
141 views
Diagonalization using LAPACK
Say, we have a Hamiltonian which for simplicity does not mix particle hole sectors. It is just a simple Hamiltonian in real space as shown,
$H=\sum_{ij,\sigma} A(i,j)(c_{i\sigma}^{\dagger}c_{j\sigma} +...
1
vote
2answers
85 views
Numerical minimization of the action in python
I want to find the trajectory $x(t)$ which minimizes the action $S = \int_{t_i}^{t_f} L(x(t), \dot{x}(t)) \mathrm{d}t$ numerically.
I am trying to do it by discretizing the action so it is more of a ...
0
votes
3answers
518 views
Draw magnetic field lines or vector field of a magnetic dipole - Python/Matplotlib
In the Wikipedia article on magnetic moments, subsection "Effects on environment" defines the magnetic field H of a magnetic dipole moment. Additionally the magnetic field lines of this ...
0
votes
0answers
24 views
How to define "Characteristic length in Ansys CFX Power Syntax script?
I am trying to evaluate Reynolds number in Ansys CFX 2020 R2 using CCL/Perl script on different domains in a radial turbine. But for that, I need to define the Characteristic length. So I define the ...
1
vote
0answers
106 views
Open-source Hexahedral meshing tools
I'm looking for an open-source automatic meshing tool or library able to generate full or dominant hexahedral mesh starting from a provided arbitrary model i.e. a surface triangular mesh stored in STL ...
-1
votes
1answer
38 views
Trouble Estimating Motor Parameters with Least Squares in MATLAB
Basically, I'm trying to use Least-Squares to estimate the parameters of a DC motor.
My system can be modeled by the following matrix equation:
$$\begin{bmatrix}V_{input}(t)\\0\end{bmatrix}=\begin{...
1
vote
1answer
95 views
Solution of Coupled Differential equation for a 2d linear flow using RK4 method in python 3
I want to study the dynamics of a 2d linear flow, whose dynamical equation is- $\begin{pmatrix} \dot{x_1}\\ \dot{x_2}\\ \end{pmatrix}=\begin{pmatrix} 1 & 1\\ 4 & -2\\ \end{pmatrix}\begin{...
6
votes
2answers
6k views
How to properly calculate CPU and GPU FLOPS performance?
Problem
I'm trying to calculate CPU / GPU FLOPS performance but I'm not sure if I'm doing it correctly.
Let's say we have:
A Kaby Lake CPU (clock: 2.8 GHz, cores: 4, threads: 8)
A Pascal GPU (clock: ...
1
vote
0answers
32 views
I'm trying to add a colour to the LogicalVolume in Geant4. I get the error that fVisAttributes and visAttributes are undefined. How can I fix this?
I'm trying to add a colour to the LogicalVolume which has been renamed to TrackerLogical in Geant4. I get the error that fVisAttributes and visAttributes are undefined although I have defined them in ...
6
votes
3answers
136 views
Coroutines for ODE solvers
Are there any ODE solver packages that use coroutines and yield their results instead of functions and returning?
Briefly, a subroutine in a programming language does some computations, returns a ...
1
vote
2answers
135 views
Writing code on the CPU while developing, running it on the GPU when live - which approach?
In my simulations I am using dense matrix-vector multiplications and 2D-fft transformations quite often, for matrix sizes of 8kx8k and up. Hence, I assume that using a GPU is beneficial for speeding ...
0
votes
0answers
54 views
Is it possble to do this complex symbolic calculation with Matlab?
Sorry it's bit abrupt, but recently I am caught up in some symbolic calcualtion which is tedious and almost impossible with mere human hands, so just wondering is it possible to solve the double ...
14
votes
3answers
535 views
What guidelines should I follow for simulation software projects?
I am not sure whether this question belongs here, but I would like to give it a try and benefit from the experience of the people at scicomp.SE.
From my experience, the software quality in ...
1
vote
1answer
91 views
Manual for library Libxc
Where can I find the manual for software library Libxc for exchange-correlation functionals? Links with domain www.tddft.org don't work.
11
votes
1answer
429 views
How should errors be reported in scientific libraries?
There are many philosophies in different software engineering disciplines about how libraries should cope with errors or other exceptional conditions.
A few of the ones I've seen:
Return an error ...
1
vote
1answer
69 views
Best way of storing numerical data in a compact manner, while leaving it accessible for tools like GnuPlot?
My simulation, written in C++, generates a large amount (roughly ~500) of text files for each set of parameters I try to simulate, with four columns of ~5k double values in each file. Furthermore, to ...
1
vote
1answer
103 views
Software for parallel incomplete LU factorisation
I am looking for a software package to compute incomplete LU factorisations in parallel. Further considerations are:
The package must allow for arbitrary level-of-fill or threshold-based truncation. ...
0
votes
1answer
34 views
Software for cellular automota
I would like to do simulations using cellular automata to describe the behavior of influenza. What software do you recommend?
4
votes
3answers
645 views
Best software to do big number calculations quickly
I am trying to do some work on some math conjecture. I am testing the conjecture numbers using very large math numbers (100+ digits ). I am currently using python to test these numbers.
In the ...
5
votes
1answer
294 views
Integrating/Implementing NURBS-related calculations
Recently, I started to develop some codes that use NURBS (general things I intend to use/already using: spline generation, interpolation, grids, isolines, closest-point find, and many others), both ...
0
votes
1answer
112 views
Which free library should I use to perform cutting/clipping operation?
I have a set of points which forms a closed loop, and I want to perform cutting/clipping a 3D model using this loop. I have used VTK but in some cases, it has a "Cannot follow edges" problem.
Is ...
1
vote
0answers
58 views
Magnetostatic modelling Radia: Increasing distance between magnets a produces positive force until a certain point, beyond which force goes haywire
I have two sets of magnets. One set consists of two electromagnets (Shown below: Blue) and the other set consists of two NdFeB N40 permanent magnets. Both sets of magnets lie on the same plane. I want ...
0
votes
1answer
84 views
Help understanding this numerical surface integration technique?
I'm attempting to write a FORTRAN program that calculates the magnetic field, B, at any point outside of a bar magnet.
I'm going to use a first order euler scheme, where each side of the bar magnet ...
0
votes
1answer
663 views
Finite volume software packages
There are many software packages for the finite element method, of which the most popular are listed e.g. on Wikipedia. When it comes to the finite volume method, I'm not aware of any similarly ...
0
votes
1answer
89 views
Converting acceleration over time to velocity or speed in code
I have acceleration data from a sensor. X Y & Z.
I move the senor in the Y axis. Mostly in a straight line. So I ignore x & z.
From the sensor documentation
5.2.1 Acceleration output：
ax=((...
1
vote
0answers
215 views
Solving complicated coupled ODE using RK4/ODE45 in Matlab
I have the following coupled differential equations also known as Guiding Center Approximation. It is used to explain the position- and velocity change of particles (electrons and protons, N = 1000) ...
0
votes
2answers
80 views
Software that does naïve or formal simplification of mathematical expressions
Devil-may-care that I am, suppose that I wanted to 'simplify' the following expression, utterly ignoring the fact that it's very naughty to raise various kinds of numbers to arbitrary powers or to ...
3
votes
1answer
795 views
Numerical propagation of a density matrix using Liouville von Neumann equation
I want to look at time evolution of the density matrices of some, very simple, spin systems, but I am having trouble with my approach.
I want to use a simple for-...
0
votes
1answer
40 views
What software packages are designed towards modelling the radiation from accelerated charges?
I'm interested in modeling the electromagnetic fields radiated from an accelerated charge, but do not want to reinvent stuff if possible. I suspect there are software packages already out there which ...
0
votes
2answers
246 views
Is there any scalable machine learning tool like molecular dynamics software NAMD?
I work in Molecular dynamics of biomolecules. I am familiar with the software NAMD. We use NAMD in our CPU cluster with the aid of mpirun.
Without GPUs can I implement large scale deep learning?
...
4
votes
3answers
3k views
How to solve the transcendental equation: $\tan(x) = \frac{2x}{x^2-1}$
I'm interested in finding the roots of the following equation:
$\tan(x) = \frac{2x}{x^2-1}$.
It is easily seen that 0 is a root and the roots are symmetric w.r.t. 0.
I wonder if an analytical ...
0
votes
1answer
156 views
Find hidden sequence $a_n = a_{n-1} + T $ , with period $T$, given some “random” numbers
I have this data plotted on a graph in which all points have the same value on the y-axis, e.g a constant integer "c", while the x-axis is the time in seconds.
So, for a c = 25 on the y-axis, there ...
0
votes
1answer
101 views
Most suitable particle-tracking software
I have a problem for which I am trying to determine the most suitable software to use. Here is a brief description of the problem.
I have a mixture of inertial particles A and B with different ...
4
votes
3answers
952 views
Pre/Post-processor for an academic finite element solver
I'm currently developing a finite element solver for academic/research purposes. Therefore I'm searching for a pre- and postprocessor in my toolchain.
For a previous project I have used gmsh as a ...
5
votes
3answers
466 views
Visualizing the solutions of the Differential equations by varying different parameters
Actually I am interested in analyzing the soution to the ODE given as $\frac{dy}{dx} = A + By + C\sin(y) , y(l) = m$ and check how the solution gets affected like whether they exist or not depending ...
5
votes
2answers
517 views
Speeding up a linear transform using Python
In an optical wavefront propagation problem, I need to do excessive Fourier-type computations:
...
3
votes
1answer
142 views
Extracting system matrices from FEM software
I work in the field of Finite Element Methods, specifically, developing algorithms to speed up the computational time in structural mechanics problems. Till now I have been developing my code in ...
1
vote
1answer
314 views
Any FOSS MATLAB/Octave toolbox for high-speed variable precision arithmetic?
I need to use variable precision arithmetic in MATLAB for an expensive set of computation.
The vpa function provided by the symbolic math toolbox is very slow. I found a non-free alternative toolbox ...
3
votes
1answer
252 views
Software/code to extract a solenoidal (a.k.a. divergence-free) field from a 2D vector field numerically
Can somebody point me to software/code to extract a solenoidal (a.k.a. divergence-free) field from a 2D vector field numerically?
There are a plethora of papers and documents describing how to do ...
0
votes
2answers
881 views
2D mesh generator with geometric primitives
The question is exactly as the title:
Which 2D (triangular) mesh generator software can be used which has a set of geometric primitives, controlled mesh size and standard output (.vtk or something ...
1
vote
0answers
43 views
Software suggestion for simulating the stacking of sedimenting rods
I'd like to simulate the following problem:
Define some square, horizontal and hard area onto which cylinders
(aspect ratio R) sediment.
Preferably, the source of cylinders
sequentially generates N ...
1
vote
1answer
145 views
Finding the lowest $n$ eigenvalues of a band-diagonal Matrix
I have a real sparse matrix of the form
$$
\left( \begin{array}{ccc}
h_{11} & h_{12} & 0 & h_{14} & & & \\
h_{21} & h_{22} & h_{23} & 0 & h_{25} & & ...
1
vote
0answers
82 views
Spherical Harmonics: band-limited representations of a vector field on a sphere
I have used pyShtools in the past to expand scalar functions to spherical harmonics and to synthesize band-limited representations of them. However, I am not too sure how to achieve this for a vector ...
-3
votes
1answer
61 views
Why Binary language is used as a first language for the Computer Systems not a high level Language? [closed]
--> why computers not used high level language as a first Language what are the main reasons?
1
vote
0answers
60 views
Book Recommondation for the time-dependent Schrödinger equation [duplicate]
Can you recommend a good book that discusses several methods for the numerical solution of time-dependent and time-independent Schrödinger equation? I have searched the internet several times but ...
7
votes
0answers
137 views
What is some of the best software design you've seen in a numerical code? [closed]
I don't think I've ever seen any scientific computational software that I would consider "good" in terms of software design. I don't mean in terms of functionality, but in terms of good high-level ...
1
vote
2answers
62 views
Automatic motion recognition
How difficult is it to program an automatic software using C that is able to read astronomy images of up to 4096x4096 pixels (or other sensor geometries), search ...
