1
vote
0answers
7 views

Find the set of K elements between n that maximize the total distance

Given a set $Q$ of $n$ points, we want to find the subset $S_\max \subset Q$ of $k$ elements that maximize the total distance between them. $$S_\max = \max_S \sum_{\substack{ i,j\in S\\ i \neq j}} ...
0
votes
0answers
2 views

What are interpolation and extrapolation in regards to Neural networks?

I'm studying for a test, and one of the mock questions is (roughly translated): Analyse the MLP's capacity of generalization in terms of interpolation and extrapolation. My notes weren't very helpful ...
0
votes
0answers
12 views

1D Advection Implementation of WENO and ENO on Python

I'm trying to implement 1D advection solver using WENO and ENO schemes. I found this tutorial on the web by Jed Hesthaven with matlab implementations. ...
0
votes
0answers
28 views

How to initiate spirals in this model?

I am trying to reproduce Tang & Othmer paper which is related to excitations and oscillations in G-protein model in Dictyostelium discoideum, an amoeba species. The mathematical model in the paper ...
0
votes
0answers
22 views

basic and simple algebraic multigrid code

I am looking for a basic and simple algebraic multigrid code to have a better understanding of this method and get an idea to start write my code (in C#). I found some codes online like : AMG1R5 , ...
0
votes
0answers
20 views

How to solve coupled linear systems resulting from 3D Laplace Equation in spherical coordinates?

Question I have two coupled linear systems for two sets of constants $C_n^m$ and $S_n^m$, where $n\geq m$ and both $n$ and $m$ start at $0$. The $S_n^0$ are not relevant, and can be set to zero. The ...
0
votes
0answers
4 views

DICOM Image Orientation evaluation in Java

I have been trying to find this out since a long time, but due to lack of any experience in Java, I am totally lost. I want to do some operations in DICOM in Java. I have used ImageJ library to simply ...
-2
votes
0answers
7 views

NASTRAN : MODAL ANALYSIS SOL 103 of an assembly of a superelement and a finite element model

I need to do a modal analysis of an assembly of a superelelment with a finite element model on Msc Nastran. This is what I have in the f06 file : SYSTEM FATAL MESSAGE 6144 (MERGE1PR) *THE SIZES OF ...
0
votes
2answers
50 views

Vector and index notation equivalence

Given 2 vectors $\mathbf{u}$ and $\mathbf{v}$ the following are equivalent: $\mathbf{u}\cdot\mathbf{v}$ $\mathbf{u}^T \mathbf{v}$ $u_i v_i$ $v_i u_i$ $\mathbf{v}\cdot\mathbf{u}$ ...
1
vote
0answers
55 views

Sparse Linear Algebra vs Dense Linear Algebra

I am interested in a reference in the literature that discusses the performance of Dense Linear Algebra (blas routines) and dense linear algebra (sparse blas routines). I am interested in knowing for ...
0
votes
0answers
39 views

Fitting high frequency trading model

I have a high frequency time series of the bid and ask prices of a stock recorded on every tick. For each data point I also have a certain indicators that predict the future movement of the price. The ...
0
votes
0answers
19 views

How can I solve a cylindrical parabolic pde with variable coefficients [on hold]

I need to solve a parabolic PDE on cylindrical coordinates with variable coefficients.
0
votes
0answers
11 views

Constraint condition in comsol [on hold]

In Comsol I am working with general form of PDE. I have made a rectangular geometry and solving equation for that. In this there are two condition as Initial value and zero flux are in-built. I want ...
0
votes
1answer
47 views

Is this the correct procedure for calculating matrix spectrum?

I am not sure if my question is on topic but I have a piece of Fortran code that is used to perform successive over relaxation. Prior to performing successive over relaxation the author is calculating ...
5
votes
2answers
79 views

Selecting most scattered points from a set of points

Is there any (efficient) algorithm to select subset of $M$ points from a set of $N$ points ($M < N$) such that they "cover" most area (over all possible subsets of size $M$)? I assume the points ...
-1
votes
0answers
29 views

New To Computer Science! [on hold]

I am newly embarking upon a journey in which I aim to learn the skills required to become a software developer, at this very moment I am unsure exactly what field I wish to go into ie. Artificial ...
1
vote
2answers
35 views

Wrapping grid of points around curvature of an infinitely long cylinder

I have an infinitely long cylinder defined using radius a point in 3d Axis defined using a 3d vector I have a set of points with 3d coordinates placed in a grid. I want to wrap this grid of ...
0
votes
0answers
19 views

Feedforward net lagged prediction [duplicate]

I am trying to predict y(t+1) of a function by using a feedforward neural network with Matlab. The inputs are the previous 3 previous values (y(t-2), y(t-1), y(t)) and the training output is the ...
0
votes
0answers
20 views

Feedforward net lagged prediction

I am trying to predict y(t+1) of a function by using a feedforward neural network with Matlab. The inputs are the previous 3 previous values (y(t-2), y(t-1), y(t)) and the training output is the ...
0
votes
0answers
26 views

Solve automatic a X by X puzzle [on hold]

I have developed a puzzle game when the user has to move (slide) cubes to the right place and see the original picture before it was scrambled (pic attached). I want to add a "help me" button that ...
2
votes
1answer
69 views

BLAS, LAPACK or ATLAS for Matrix Multiplication in C

I am trying to find the most optimized way to perform Matrix Multiplication of very large sizes in C language and under Windows 7 or Ubuntu 14.04. And searching led me to BLAS, LAPACK and ATLAS. ...
0
votes
1answer
21 views

Power series regression linear fit in VBA excel

I wrote a program that calculates the best fit in VBA excel for the following model $$ y_k=c_1x_k+c_0+c_{-1}(x_k)^{-1} $$ solving for the best fit parameters $c_1$, $c_0$, and $c_{-1}$. However I ...
1
vote
1answer
41 views

How to update velocity to include pressure when using P2/P1 elements

I am in the process of writing a finite element code to solve the Navier-Stokes equations using the theta method for time stepping (basically Crank-Nicholson for diffusion and forward Euler for ...
2
votes
1answer
26 views

Simple Path to Route Algorithm

I'm currently conducting research into subway paths, but stand in front of a problem, with no programming knowledge and an extremely short time-limit. Probably the question I am asking is trivial, ...
0
votes
0answers
18 views

Water Properties IAPWS-IF97 implementation on C/C++

I'm Looking for an implementation of the IAPWS-IF97 water properties on C/C++. I'm aware of the library freesteam. However freesteam does not include all the properties I'm looking for. Particularly I ...
1
vote
1answer
59 views

What are acceptable boundary conditions for porous media flow?

I am attempting to simulate fluid flow through a porous foam. I would like to have no-slip boundary conditions on part of the boundary and free flow conditions on the inlet and outlet. Right now I am ...
0
votes
0answers
21 views

can I cast $\mathrm{vec}(X^TX)$ with matrix $X$ into quadratic form of $\mathrm{vec}(X)$

I want to cast $\min \mathrm{tr}\,J(X^TX-C)$ where $J=$ all one's matrix (this is just sum of all elements in $X^TX-C$) with matrix $X$ into standard quadratic program. The natural way is to use ...
2
votes
1answer
92 views

Solve $AX = B$ where $X^T X = C$

Is there a natural way to find the solution to $$AX = B, X^TX = C \enspace \text{?}$$ $X$ is a matrix and has a small number of rows, and $A$ is sparse. An approximate solution would be fine.
3
votes
2answers
115 views

What's the difference between C0 penalty methods and Discontinuous Galerkin methods?

I am trying to understand the DG FEM methods, but I got lost in their definitions. In some papers I read that the "C0 penalty method" is one example of the DG method, but sometimes they are separated ...
1
vote
0answers
62 views

Linearization of two phase flow iteration for Newton Method

I am trying to implement a numerical model to solve a two-phase flow using the Newton-Raphson method. To do so, I also have to differentiate the fluid pressure $P$ with respect to the matrix velocity ...
3
votes
2answers
119 views

1D inhomogeneous Poisson PDE with Dirichlet BCs, slow convergence

For an assignment I have to implement a 1D Poisson PDE with inhomogeneous Dirichlet BC's $$\Delta_1 u = f, \quad u(a)=g(a), \: u(b) = g(b) $$ I have managed to make it work, but I am not seeing the ...
-5
votes
0answers
24 views

What Data mining techniques are used at Facebook? [closed]

What are the data mining tools/techniques used by Facebook and how they are utilizing this data? Please provide examples.
1
vote
1answer
91 views

Please explain the meaning of these Boundary conditions [closed]

I am trying to learn Gmsh and Fenics and was looking at an example which shows the application of Boundary conditions on a simple Poisson problem. Here is the link: ...
1
vote
0answers
32 views

Nonlinear 2D modeling of Neural Electromagnetic field in Matlab

I am trying to replicate the MATLAB simulation presented in this paper. More specifically, I have to code the solution to this equation $$\frac{a}{2R_i}\frac{\partial^2 V_m}{\partial x^2} - ...
0
votes
0answers
20 views

Implicit time integrator for Chebyshev collocation method for linear hyperbolic system

I want to solve linear hyperbolic system using Chebyshev collocation method. As this method puts severe constraint on the time step for the explicit time integration, I decided to switch to implicit ...
3
votes
2answers
84 views

How to calculate efficiently mesh edges midpoints?

I have a 2D mesh of triangles used in Finite Element method to discretize the domain. I want to calculate the midpoints of all the edges because I want to use $\mathbb{P}^2$ elements. I am using ...
0
votes
0answers
23 views

Finding parameters of a gaussian mixture model that uses markov models

I'm using this paper for reference http://www.cs.cornell.edu/~asaxena/learningdepth/saxena_ijcv07_learningdepth.pdf I could get all the features required but have trouble with the probabilistic model. ...
2
votes
2answers
91 views

Solve non-linear set of three equations using scipy

I need to solve a non-linear set of three equations using scipy. However, I do not have any clue on which algorithm is suitable for my problem from a mathematical point of view (stability, ...
1
vote
1answer
34 views

Finding Common Side of Triangle

Given a triangulation (geometry), are there known algorithm in finding common side of triangles, that is O(N) or better?
3
votes
1answer
112 views

Challenges in implementing Algebraic Multigrid on millions of processors

I just implemented an Algebraic Multigrid solver for a Mixed Dirichlet-Neumann Boundary Value problem and was surprised to see the speed-up as compared to a simple iterative solver for a large problem ...
0
votes
1answer
29 views

Paraview: Multiple csv files to time series

I have multiple CSV files with point-coordinates and, possibly, multiple data values attached to them, i.e., the rows look like x y z data1 data2 ... Is there ...
4
votes
1answer
37 views

LP and SDP nomenclature

A canonical form of primal linear program is $$ \text{minimize } c^T \cdot x \\ \text{subject to } Ax = b, x \geq 0 $$ The dual is $$ \text{maximize } b^T \cdot y \\ \text{subject to ...
3
votes
1answer
73 views

Trust-region Newton: implementation issue with Conjugate Gradient calculations

UPDATE: The problem turned out to be the step (refer penultimate paragraph below) where I was factoring out a small value from the vectors of the numerator and denominator and then computed dot ...
0
votes
1answer
26 views

How do I generate maxwell-boltzmann variates using a uniform distribution random number generator?

I am doing a molecular dynamics simulation. I need to assign initial velocities to the atoms. I want to assign the initial velocities which follow the maxwell-boltzmann distribution. How do I ...
1
vote
1answer
91 views

How to make this matrix efficiently?

Originally posted on stats.stackexchange, I'll pair the post down to something a bit more general. Suppose I have vectors $\{\mathbf{\delta}, \mathbf{x}_1, \ldots, \mathbf{x}_J\}$, where $\delta \in ...
0
votes
1answer
28 views

Converting linear BIP constraints into convex hull

Given a linear BIP $$\text{Minimize}\;\;\;c^Tx$$ $$\hspace{6.5mm}\text{Subject to}\;\;\;Ax\leq b$$ $$\hspace{38mm}x\in\{0,1\}^n$$ We can in theory convert the constraints to the convex hull ...
0
votes
0answers
49 views

How one can explain to have non-unique numerical solution at the interface boundary?

If the existed computational domain is divided into two pieces and developed numerical scheme is applied to these lets say right and left side domains of the interface individually to obtain two ...
3
votes
0answers
39 views

Stability analysis for explicit time discretization in the Finite Element Method

I have been looking for stability analysis of general reaction-diffusion problems, of the form $\frac{\partial u}{\partial t}=\nabla\cdot D\nabla u-k\,u$ , to be solved using the standard Finite ...
0
votes
0answers
22 views

Converting a labelled pixel grid to an isoregion geometry file

I am working with ASCII text files that each contain a grid of integer labels. The grid can be interpreted like the pixels of an indexed raster image. e.g. $\begin{pmatrix} 1& 1& 1& ...
0
votes
0answers
31 views

Eigenvalues from graph (modal)

I am a power engineer analyzing the dynamic response to system events. I am trying to re-create a modal analysis function from older software in python. In this context modal analysis is taking a ...

15 30 50 per page