# All Questions

9,023 questions
Filter by
Sorted by
Tagged with
66 views

### How can PDE matrices be identified?

I need to include experimental results for lots of PDE (partial differential equation) matrices in my research work. How can I identify PDE matrices? For example, matrices in the UFL Sparse Matrix ...
299 views

385 views

### How to represent molecules and compare equality

I originally asked this question at StackOverflow, and was suggested to bring it here. I've seen this question about the representation of molecules in memory, and it makes sense to me (tl;dr ...
242 views

### Statistical analysis of optimization algorithms

If we optimize some parameter using 4 optimization algorithms, 2 of which are population based (say A and B) and 2 trajectory methods (single point search)(say C and D); what statistical test can be ...
38 views

### Implicitly defined univariate function

So my fellow numerical computational peeps it may be that I am suffering from sleep deprivation but I'm struggling to numerically compute a function $u \rightarrow h(u)$ defined implicitly as follows: ...
112 views

### How to determine the number of c points in algebraic multi grid

I am trying to write an algebraic multi-grid solver (in c++). At a given level I determine which nodes are c-points and which nodes are f-points (where the total number of c and f points equals the ...
199 views

### jump conditions for Poisson/Darcy equation in primal form versus mixed form

Consider the Darcy equation, $$\mathbf{v} + \dfrac{k}{\mu_0}\nabla p = \mathbf{f} \\ \mathrm{div}\; \mathbf{v} = 0$$ If the coefficient $k$ is piecewise constant across an interface $\Gamma$ in the ...
475 views

### Python: Computation time Issue with mpi4py

I am using in Python mpi4py to process in parallel 20 minimization functions. Each of the 20 worker processes the same algorithm but with different random initial ...
138 views

### Writing a 3D array from Petsc

I am trying to do something fairly simple somehow I have made it hard. Is there an example of how to send a 3D array to a binary file?
65 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 ...
59 views

### Should I use bestman2 or dcache CLIs (srmping, srmls, etc..)

I am fairly new to using SRM, and I am wondering if I should be using srm CLI tools (srmping, srmls, srmcp, etc..) provided by dcache, or bestman2 counter parts (srm-ping, srm-ls). I used to think ...
73 views

### How many years it would take our laptops to be as fast as the fastest super computer in 2000 [closed]

How many years it would take our laptops to be as fast as the fastest super computer in 2000 according to Moore's law?
70 views

### Finding roots without knowing much about the function

Consider solving numerically for roots: $( x_0, y_0): f(x_0, y_0) = 0, g(x_0, y_0) = 0$ where you only know that f, g continuously differentiable but the theoretical differentiation is not a ...
69 views

### Particle Collision to Static paticles

I have a system of particles with equal distance with each other and another at random positions which is moving with time. I want to know: a) The method by which I can reduce the number of particles ...
536 views

### Solver for large non-linear system of equations

I am curently using R package nleqslv for solving a non-linear system of equations with 300 variables. I need to scale this to the system with ~50k variables and naturally this does not scale very ...
472 views

### MATLAB Newton non-linear equation

I have the following non-linear equation: where $w0=0.25,w0=0.5,w0=0.75$. I have to prove that if $k$ is a root, then also $−k$ is a root and that there exists only one $k∈(0,1)$ root, but my MATLAB ...
420 views

### Elastic LP Programming

Say I have an LP that is unfeasible and that I want to find the solution that makes it feasible without strongly violating the current constraints. What is a principled way of solving this problem, ...
80 views

### Rank of image intensity matrix

I've been reading a paper about using Matrix Completion for Photometric Stereo but I am having some troubles in section 2.2 trying to understand why irrespective of the number of pixels and the number ...