# All Questions

2 views

### FEM with soil slope

I what to calculate displacements, stress and strain in a soil slope with a FEM script. The slope moves like a laminar flow. Can you suggest me some bibliography on this problem? I've already look on ...
36 views

### How to test convergence of an algorithm for constrained optimization

I am applying an iterative method (projected newton) to an optimization problem. Theoretically, the method should converge linearly. I would greatly appreciate it if you could share how should I test ...
19 views

### The solution found by the optimization function when exitflag is negative

I'm using Matlab's fmincon to solve a constrained nonlinear optimization for varying sets of parameters in the objective function. I have 2 parameters and have 400 unique combination of these 2 ...
7 views

### Finding correlations between sparse data with different temporal bases

The problem was one that came up during a standards committee meeting. If have one channel of data sampled every 100ms to record fault codes on a system (say an gasoline engine). It records value ...
15 views

### convergence interval of an infinite series without the general term

I am trying to find the convergence of an infinite series of which I do not have the nth term. Instead of applying the ratio test for the nth term, I divided the first two terms, then the next two and ...
35 views

### how do I know is my GPU work?

When I did my simulations I am test my Nvidia Tesla c2075 if its work or not ? so according to my attached photo , that's mean its not working ? I am already enable GPU on starting Fluent 15
47 views

### difference of polytopes in $\mathbb{R}^n$

Is checking the equivalence of two convex polytopes $p^{s}$ and $p^{t}$ NP-hard? $p^{s}= CH\{ \cup <p^{s,a_1},...., p^{s,a_m}> \}$ // CH is convex hull computed on union of a polynomial ...
59 views

### Tanh-sinh quadrature numerical integration method converging to wrong value

I'm trying to write a Python program to use Tanh-sinh quadrature to compute the value of $$\int_{-1}^1 \frac{dx}{\sqrt{1-x^2}}$$ but although the program converges to a ...
46 views

### solving a non-linear equation with integrals involved

I would like to solve the following equation, wrt $n(e)$ $$f(n(e))=g(n(e)) + \int w(n(e))de$$ The integral there it confuses me. Any suggestion on how I can implement this on a the computer (I am ...
47 views

### Cloud solutions for microscopy image analysis

At our research facility we routinely perform what are called PALM (Photo-activated localisation microscopy) or STORM (stochastic optical reconstruction microscopy) experiments. You can read all ...
27 views

### What are the numerical methods for huge polynomial systems?

Let a system of $n$ polynomial equations of degree $d$ with $m$ variables. I'm interested in a sparse system with $d = 3$, $n \sim 2000000$, $m \sim 50000$ and integer coefficients. What techniques ...
13 views

### What is the difference between continuous-time waveform relaxation(CWR) and discretized waveform relaxation?

What is the difference between continuous-time waveform relaxation(CWR) and discretized waveform relaxation? I am just confused ...
66 views

### Pre calculate mathematical expressions in Fortran 90

Is there some flag to let the Fortran compiler pre calculate a math expression before compiling it?. I have to write expressions that contain many small 4x4 matrix multiplications. The thing is, most ...
156 views

### Understanding the cost of adjoint method for pde-constrained optimization

I'm trying to understand how the adjoint-based optimization method works for a PDE constrained optimization. Particularly, I'm trying to understand why the adjoint method is more efficient for ...
26 views

### Algorithm for porosity based CFD mesh

I am writing the pre-processing program for a porosity based CFD project. I have a mesh made of cubes, and need to import an object (a stl file: triangular mesh, not solid) over it. The cubes will ...
36 views

### Open several dependent functions in matlab with scripting

I have several matlab functions and one script that call those functions. Suppose that they are 'a.m' 'f1.m' 'f2.m' and 'f3.m'. The script 'a.m' must open the functions files when it is manually ...
67 views

### How to minimize the artefact of a cartesian to polar transform followed by a polar to cartesian transform?

I'm transforming cartesian images into polar images. (x,y) => (angle, radius) I fill the polar image by iterating on each of its pixels and filling them by doing the reverse polar transform. For a ...
17 views

### Non linear system of equations with discretization on k-space

I want to numerically solve the following system of differential equations at the steady state: \begin{aligned} \frac{\partial \rho_{11\mathbf{k}}}{\partial t} =& ...
72 views

### Discrete Poisson Equation with Pure Neumann Boundary Conditions

I'm trying to implement the Helmholtz-Hodge Decomposition in 2D, which states that a vector field is composed by a rotational free component, a divergence free component and a harmonic component. ...
45 views

### use Matlab's PDE toolbox to solve PDE with variable coefficients [closed]

I'm new to the PDE toolbox in Matlab. From the PDE specification window of the toolbox, it looks like one can only solve PDE with constant coefficients. How can ...
43 views

### Calculating periodicity of a pseudo random number generator (Middle-square method) [closed]

Below is a Python code that calculates the periodicity of the middle-square method for a given 4 digit-numbers: ...
37 views

### Issues with Open MPI [closed]

Not sure if this question is more appropriate for StackOverload, but I'm guessing a bunch of people here have experience with MPI2, so thought I would try here first. I have some large dense complex ...
91 views

### Numerically compute one-to-one mapping

I have a set of points defined by their coordinates $(x_1,y_1)$ after changing some parameters of the problem I obtain a second set of points defined by their coordinates $(x_2, y_2)$. There exists a ...
12 views

### Any software that can symmetrize input sets?

Is there any software that contains symmetrization techniques ex. polarization, Steiner Symmetrization etc. I suppose not. Which software would you suggest for rigid transformations? Thank you
105 views

### Comparing Eigenvectors, Mathematica vs. Matlab

I am trying to create the same out puts in Mathmatica and Matlab, however I am running into trouble aligning the eigenvectors with the eigenvalues, I think the Matlab is doing something slighly more ...
65 views

### rank-deficient NNLS

I want to find the minimum-norm solution to a rank-deficient least-squares problem, subject to positivity constraints, e.g. $$\min_x\ \|x\|^2 \quad s.t.\quad Ax = b,\ x \geq 0$$ where $A$ is large, ...
32 views

### Signal balancing using SVD: notations and implementation in R

Hibbs et. al use SVD to balance the strength of different underlying signals in gene expression data using the following decomposition: $X_{m*n} = U_{m*n} \Sigma_{n*n} V^T_{n*n}$ In this case $U$ ...
23 views

### Convex hull and cartesian Product

Under which conditions, the cartesian product of some closed and bounded polytopes is equivalent to their convex hull?
44 views

### Fast way to compute all eigenvalues of a dense Hermitian matrix

I am finding the eigenvalues of dense NxN Hermitian matrix which is calculated from a density operator in quantum physics. All the eigenvalues are needed as I need to calculate the sum of the absolute ...
157 views
+50

### What is the current state of the art in solving higher dimensional parabolic PDEs (multi-electron Schrödinger equation)

What is the current state of the art for solving higher dimensional (3-10) parabolic PDEs in the complex domain with simple poles (of the form $\frac{1}{|\vec{r}_1 - \vec{r}_2|}$) and absorbing ...
156 views

### 0,1 binary polynomial programming

Is there a mathematical optimization branch that explicitly tries to optimize this (type) problem? \eqalign{ & \min \cr & \sum\limits_{i = 1}^N {(J*s[i] + {J_1}*s[i]*s[i + 1] + ...
31 views

### Appropriate algorithm for (non-linear) ODE with integral equilibrium constraint: collocation?

I have a problem of the following structure: For some scalar $g$, functions $F(z)$ and $h(z)$ defined on $[0,\bar{z}]$ , and a non-linear operator $\phi(F,z)$ (in reality, $F$ and $h$ are vector ...
40 views

### Permission denied with diary command

I am trying to use the diary function in Matlab: ...
56 views

### Lua and Fortran (or Python) I/O

I am writing a global climate simulation software system. My idea is the following : At the top of everything, I interface to the OS using D, a very powerful language for compile time code ...
17 views

### COMSOL: String vibration modeling using Wave Equation PDE

I am learning comsol and already could make the vibration of a string in 1D (geometry used there was an interval) - I saw 2D plot and the string was vibrating, also I could do the same in 2D ...
49 views

### Suggestions for open source C++ library for medium scale non-linear solver

I need to find the root of a nonlinear system (which comes out of collocation, so I will change the order to test). I will likely have about 50-300 variables, and the Jacobian is going to be ...
28 views

### Solving a problem using multiple threads using CLP

Is it possible to run Clp on multiple threads using Julia and JuMP?
73 views

### Levenberg-marquardt: How to calculate the jacobian with fixed parameters

So I'm working on a fitting algorithm using the levenberg-marquardt algorithm and I'm a bit stumped as to how to handle fixed parameters. Looking around at other code, like the minpack version of the ...
110 views

### Open source auto-differentiation for MATLAB?

Are there any open-source auto-differentiation libraries for MATLAB? I am aware of commerical packages such as http://tomopt.com/tomlab/products/mad/ and plenty of C++ libraries, but I can't find much ...
148 views

### Is it well known that some optimization problems are equivalent to time-stepping?

Given a desired state $y_0$ and a regularization parameter $\beta \in \mathbb R$, consider the problem of finding a state $y$ and a control $u$ to minimize a functional \frac{1}{2} ...
53 views

### Does it make sense to build ATLAS from source on a cloud machine?

ATLAS is an extremely popular linear algebra library. When you install ATLAS from source, it tries to automatically tune a number of parameters to give you the fastest code. Does it make sense to do ...
43 views

### ode45 solver MATLAB improve time

I am numerically simulating the Mathieu equation using ODE45 and I have to keep changing the parameters delta and epsilon for each simulation to get the required peiodic solution. Following is the ...
33 views

### eigenvalue of small symmetric matrices

If I am to solve a symmetric eigenvalue system $A=QDQ^T$, where $A\in\mathcal{R}^{n\times n}$ and $n$ is small (in the range 4 - 64); I want all the eigenvectors and eigenvalues; There are two major ...
25 views

### Generating start point in a systematic manner for fmincon

I'm trying to generate start points for my optimization problem in Matlab. At this point Im not worried about feasibility but only a fast way to generate the points from which I could test the ...
32 views

### Generating Hessian of the Lagrangian with dynamic number of nonlinear constraints in Fmincon

I'm using interior point algorithm for solving a nonlinear optimization problem and want to provide Hessian of the Lagrangian as part of fmincon to speed up the process (running couple of thousand ...
31 views

### OpenCL C Matrix Multiplication over Multiple Runs

I am attempting to translate a dgemm / MPI matrix multiplier onto the GPU through OpenCL C. My issue is that the code below gives the correct output for a 9x6 matrix being multiplied by a 6x450 ...
37 views

### Fast way to compute barycentric lagrange interpolation

Is there any fast way to compute the barycentric Lagrange interpolation using matlab? something more faster than using repmat instead of for loops
24 views

### prove optimality only by cutting without branching (gurobi)

I have a MIP which I know the solution almost for certain. I want to use gurobi to prove that the true solution (even if it is not the one i provide) shall not lie more than 0.5% deviated from the ...