0
votes
0answers
6 views

Synchronization of chaotic neural networks

I am trying to plot the graph of chaotic impulsive neural networks and I have written the following MATLAB code for the same: However, I am getting the Warning: Failure at $t=4.831354$. Unable to ...
1
vote
0answers
10 views

inertia count sparse matrix with dense low-rank perturbation

I would like to determine the number of negative eigenvalues (inertia count) of the $(N \times N)$ symmetric real matrix $K - \sigma M$, with $K$ a positive-definite sparse matrix and $M$ a positive ...
4
votes
1answer
29 views

Benchmark problems for eigenvalue reordering algorithms sought

Every real matrix $A$ can be reduce to real Schur form $T = U^T A U$ using an orthogonal similiary transform $U$. Here the matrix $T$ is quasi-triangular form with 1 by 1 or 2 by 2 blocks on the main ...
1
vote
0answers
14 views

Showing date in Paraview's Annotate Time Filter

I have a time dependent data set where each frame corresponds to a certain date. I need to show the time annotation, much like what Annotate Time Filter does, but show the date instead of time as a ...
4
votes
0answers
92 views

An invertible matrix that minimizes the norm of the product with a given matrix

Given a fat matrix $B \in \mathbb{C}^{n \times m}$ (where $m > n$) with full row rank, I would like to find (numerically) a full-rank matrix $A$ that minimizes the Frobenius norm of the product $A ...
1
vote
1answer
37 views

Calculate partial trace of an outer product in Python?

I have a python implementation of calculating the partial trace over select dimensions. ...
4
votes
1answer
87 views

What is the best numerical method for a six dimensional spherical integral?

I am trying to do integrals of the type $$ \int d^3\vec{p} \int d^3\vec{p}' e^{-p^2} e^{-{p'}^2}f(\vec{p}, \vec{p}') $$ where $\vec{p}$ and $\vec{p}'$ are three dimensional vectors represented using ...
0
votes
0answers
23 views

How to uniquely identify a GPU in a multiGPU environment using OPENCL? [on hold]

I am learning OpenCL and have written a preliminary code that will query the machine and find out the platforms and devices associated with it. ...
0
votes
0answers
24 views

Classification of sealed soils from aerial photography using machine learning

Relatively new to machine learning, I am looking for the best method to use for classification of sealed-soil from remote-sensing data. As a try-out, I would like to start by identifying streets and ...
1
vote
1answer
100 views

Does a generic method for solving a system of PDEs exist?

There are generic methods for solving systems of ODEs numerically. Are there generic methods for PDEs? If so, what are they? If not, why not? To elaborate... Any set of ODEs can be written in ...
-4
votes
0answers
22 views

How Fluctuations can be removed from a graph? [on hold]

Hy sir my plot is to much fluctuation at smaller values ... I set Precision upto infinity but not effective, Any tip sir
0
votes
0answers
59 views

Is it possible to solve the incompressible Navier-Stokes equations by solving just one matrix per timestep?

I'm trying to simulate the 2D incompressible Navier-Stokes equations using a finite difference scheme that uses the implicit Backwards Euler method for moving the simulation forward in time. I have ...
1
vote
0answers
26 views

Maintain sorted ring buffer [closed]

I would like to insert elements into a ring (circular) buffer one at a time and maintain a permutation array which keeps track of the sorted elements in ascending order. To do this, I have adapted the ...
0
votes
0answers
36 views

Great Habits for Creating Clean, Secure, and Portable Code [closed]

Too often, code for computational purposes can be slow, buggy, or insecure. What habits and paradigms/frameworks of thought have assisted you in your journey to create beautiful code?
0
votes
0answers
26 views

Comparing Estimates of Entropy with Theoretical of Multivariate Gaussian

I am trying to compare the effectiveness of a histogram for density estimation, by seeing how well it approximates the PDF of a normal distribution. I make use of the concept of entropy, which is ...
1
vote
1answer
35 views

Recreating this 3D density plot in ParaView

I want to do somethings similar to the plot found at the bottom of this blogpost, which I found via this post in ParaView, which seems to have been the original Application used to generate the plot. ...
1
vote
0answers
25 views

What does the Jackson Kernel measure?

A certain filter I'm writing uses two different kernels. The Fejer kernel (which is common) and the Jackson kernel: $$ \Delta_T(x) = T \,\left( \frac{\sin \pi T x}{\pi T x}\right)^2 \quad\text{and}...
0
votes
1answer
30 views

Is it possible to partition 2D data into bins such that each bin contains the same number of samples?

I am trying to sort data following a bivariate distribution into a numpy histogramdd, where each bin should contain the same number of data points (to the nearest whole sample). I expect that some ...
1
vote
1answer
46 views

Algorithm to find most similar elements in several groups

I'd like to find an algorithm that can solve the following problem: Consider 4 groups of numbers: Group 1: [10, 100, 1000], Group 2: [101, 15, 2000], Group 3: [20, 1500, 100], Group 4: [150, 3000, ...
2
votes
1answer
66 views
+50

How to transform this SOCP to the format required by cvxopt

I'm new to SOCP and want to try to get familiar with the format and how to solve it with cvxopt in python. However, for a simple toy example I'm struggling to get ...
6
votes
0answers
100 views

Fast Automatic Differentiation for numpy?

I would like to use automatic differentiation to calculate gradients to function written in numpy. I've come across a number of packages, including autograd tangent chainer But none of them seem ...
4
votes
0answers
56 views

How can Navier--Stokes equations have asymmetric solutions such as Karman vortex streets

The Navier--Stokes equations are axially symmetric, so with symmetric boundary conditions, how can features such as Karman vortex streets develop? I understand that in reality symmetry does never ...
3
votes
1answer
75 views

How does fmincon in MATLAB calculate gradients?

I am trying to solve numerically a constrained optimisation problem in MATLAB, and I am wondering how the fmincon function calculates gradients when one isn't ...
2
votes
0answers
24 views

Identifying the time window at which a meteorological factor influences tree growth the most

This is a problem I am encountering in a research project. I have thought of a naive approach to solve it which relies on many assumptions, is not guaranteed to work, and would be tedious and ...
1
vote
0answers
42 views

Derive total energy balance equation from Chapman-Enskog analysis of lattice Boltzmann equation

I'm interested to derive the total energy balance from Chapman-Enskog analysis of lattice Boltzmann equation (LBE). I know, I should go to the second moment of LBE (zeroth moment gives mass ...
3
votes
1answer
70 views

Level scheduling of triangular sparse matrices

Assume one has a triangular sparse matrix and want to solve $Lx=b$ where $b$ and $L$ are known. This can be done easily by using forward substitution when $L$ is a lower triangular matrix. Forward ...
0
votes
0answers
41 views

TetGen: Hole # in a facet does not have any coordinate

I am using a .poly file to generate a volume mesh using TetGen. My surface mesh has one hole and I have defined that in the .poly file. Every time I run TetGen it is giving me the following error "...
4
votes
0answers
57 views

Solving a PDE implicitly by iteration in python

Connected to this question here on Computational Science, I've posted a follow-up question on how to solve a PDE using an implicit scheme like Crank-Nicholson in general in this question on SO. But I ...
0
votes
1answer
47 views

How is nonlinear flux interface term assembled for Discontinuous Galerkin method for hyperbolic conservation laws?

For example, for 1D Burgers equation $$ u u_x = 0 \\ $$ equivalently, $$ \frac{dF(u)}{dx} = 0\\ F(u)= \frac{u^2}{2} $$ If I want to obtain $A_{ij},i\ne j$ for two DOFs ($U_i$ and $U_j$) of two ...
0
votes
0answers
49 views

Confusion about Rayleigh beam formulation

Sorry for disturbing you, my friends. Recently, I am reading books on Rayleigh beam theory where the rotary inertia can be taken into account without introducing rotational degrees of freedom. For ...
0
votes
0answers
14 views

XDMF Grid>Geometry>DataItem> reference to ASCII file

Consider the XDMF file below. How can I replace the explicit x-vector 0.0 1.0 2.0 3.0 in the geometry block by a reference to an ASCII file ...
8
votes
1answer
160 views

What scientific problems can be simulated that couldn’t be simulated 10 years ago?

What scientific problems can be simulated with computers that couldn’t be simulated 10 years ago? I’m particularly interested in cutting-edge scientific simulations, which wouldn’t have been possible ...
1
vote
0answers
32 views

Split step Fourier method to solve Schrödinger equation for moving potential

I'm trying to use the excellent Schrodinger Python class by Jake VanderPlas (https://jakevdp.github.io/blog/2012/09/05/quantum-python/) to simulate a wave packet within a moving Gaussian potential. I ...
0
votes
1answer
34 views

C++ library unstructured mesh writer to VTK format (or similar)

I am working on a 2D unstructured code in C++. I am using gmsh to generate a 2D unstructured mesh and reading it into my program with a library called ...
0
votes
0answers
10 views

Exotic stats problem mode fuzzy clusters python

EXOTIC STATS PROBLEM ; MODE, FUZZY CLUSTERS, ETC Hi I'm working on a math problem and not sure how to approach it. Trying to enumerate, rank and extract most common numeric ranges from a list, with ...
1
vote
0answers
33 views

How to analyze the dispersion and dissipation of a certain FEM?

In Finite Difference method or Finite volume textbook. Dispersion/Dissipation can be analyzed by set $u = u_0\exp{\omega t +\mathbf{kx}}$。 However, I cannot find something about this kind of analysis ...
0
votes
1answer
48 views

How to efficiently solve a QCQP with “dynamic” constraints in Python?

I want to solve a QCQP in Python. It is a problem from finance: maximise return (linear function) given some linear constraints and one quadratic constraint that turns it into a QCQP. Formally, $$\...
3
votes
1answer
73 views

Why Coercivity is so important in FEM framework?

I know Lax-Milgram theorem is fundamental to FEM. But it did not explain what will happen if coercivity is not met. My understanding is if it is met, eigen value of the operator (or its corresponding ...
1
vote
1answer
50 views

Piecewise-Linear Quadratic Optimization for an “Almost Convex” Problem

I have a 7-14 dimensional piecewise linear cost function I'd like to minimize with two quadratic terms of the form: $$ f(X) = X^tCX + d \sum_i |x_i-x^*_i|^2 + \sum_i P_i(x_i-x^0_i) $$ $$ \sum_i x_i ...
3
votes
1answer
110 views

Efficient implementation of preconditioners for iterative solvers

I am struggling a bit with the concept of preconditioners for iterative solvers and how to implement them efficiently. The literature mostly provides methods to create a preconditioner matrix $M$ (...
5
votes
0answers
36 views

Cressman interpolation and objective analysis

I have read this question and answer – Interpolation of scattered data to a regular grid in python and I am doing something similar as I have temperature values of the atmosphere at different heights ...
0
votes
3answers
97 views

Why is the test function space in FEM chosen with homogeneous boundary conditions?

It is so confusing, especially when I learns discontinuous galerkin method in broken Sobolev space and weak Dirichlet boundary condition. If the trial function is chosen with homogeneous boundary ...
1
vote
1answer
34 views

What is a good way to select a small subset (say 50) of items from a large pool of items (say 5 million) while minimizing an objective function?

I have 5 million items that have 10 features (all continuous and not categorical) each and would like to select a small subset of these items. Ideally, I want to manually specify 10 features of my own ...
0
votes
1answer
63 views

Simulation-based Optimization vs PDE-constrained Optimization

What is the difference between Simulation-based Optimization and PDE-constrained Optimization? Would studying a text on Simulation-based optimization be sufficient to understand and apply both?
0
votes
0answers
30 views

Help in creating 2D mesh with correct scalars

I'm making a 2D FEM program (using only quad elements), and after vtk's examples to assign scalars to the elements of my mesh, I got no good results. Basically, I have 3 arrays: The first one is the ...
1
vote
0answers
36 views

Artificial Neural Network for nonconvex optimization

I want to use artificial neural network(ANN) for solving non-convex optimisation problems. How do I map the constraints and the objective functions in the ANN architecture?
2
votes
1answer
58 views

How can a CG solver solve a non positive definite sparse matrix

I am using the CUSP CG solver and I ran it on couple of sparse matrices from the University of Florida sparse matrix collection. The solver was able to solve non positive definite sparse matrices. My ...
0
votes
0answers
59 views

Oscillations in force coefficients from CFD simulations

I have carried out a CFD simulation (with finite volume method) to investigate the unsteady force enforced to the vehicle body. The horizontal tail keeps flapping in sinusoidal function. As a result, ...
3
votes
1answer
59 views

Solving for a set of coupled ODEs to get correct variable values

My question is about how I can solve a coupled system of ODE's, and print out the variables in a plot. I am solving for an q value and an e value, seen in this set of coupled ODE's below: $$ \begin{...
1
vote
2answers
97 views

Uniform dots distribution in a sphere

I'm trying to implement Barnes-Hut algorithm, with a binary tree. My initial conditions are a uniform mass distribution in a sphere with radius $R$. How can I create uniform dots distribution in a ...

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