Computational Science Stack Exchange
Computational Science Stack Exchange

Most Popular

more tags
1500 questions
12
votes
3 answers

ODEs vs DAE vs ADE?

I am totally confused between ODEs which I am familiar with, and differential algebraic equations (DAE) and algebraic differential equations (ADE). Are they the same but just different names or what is the key difference between them (their nature…
MBM
  • 167
  • 1
  • 1
  • 5
12
votes
1 answer

Visualization of quadtree & octree grids

So-called quadtree and octree grids are quite attractive for applications requiring adaptive mesh refinement. They are for example used in Gerris and Paramesh. Is anyone aware of a good file format for such grids, and supporting visualization…
Jannis Teunissen
  • 724
  • 3
  • 15
12
votes
0 answers

Optimized open source BLAS / LAPACK package

I was wondering what is a more optimized open source BLAS/LAPACK package with respect to modern multi-core processors (Haswell and beyond). Is there any distribution that can attain performance close to that of Intel MKL for instance? In addition…
tamumiket
  • 121
  • 1
  • 7
12
votes
2 answers

Quickly finding rough lines in sets of points

In a particular class of detectors, our data comes out as pairs of points in two dimensions, and we want to string these points into lines. The data is noisy, and is binned in one direction but not in the other. We can't guarantee a hit in every bin…
dmckee --- ex-moderator kitten
  • 1,115
  • 8
  • 17
12
votes
3 answers

Can compressible flow solvers be used to solve incompressible flow?

I know that incompressible and compressible flow solvers are specifically designed to solve different types of problems with different fluid properties/flow conditions. Clearly, among the advantages of using incompressible flow solvers for modeling…
Paul
  • 12,045
  • 7
  • 56
  • 129
12
votes
2 answers

pointwise vs. continuous observations in PDE inverse problem

I work on an inverse problem for my Ph.D. research, which for simplicity's sake we'll say is determining $\beta$ in $L(\beta)u \equiv -\nabla\cdot(k_0e^\beta\nabla u) = f$ from some observations $u^o$; $k_0$ is a constant and $f$ is known. This is…
Daniel Shapero
  • 10,263
  • 1
  • 28
  • 59
12
votes
1 answer

Smallest eigenvalue without inverse

Suppose $A\in\mathbb{R}^{n\times n}$ is a symmetric, positive definite matrix. $A$ is big enough that it's expensive to solve $Ax=b$ directly. Is there an iterative algorithm for finding the smallest eigenvalue of $A$ that doesn't involve inverting…
Justin Solomon
  • 1,341
  • 7
  • 24
12
votes
2 answers

Algebraic Multigrid: Why does the product of interpolation and restriction not result in something with norm 1?

I'm currently working with "A Multigrid Tutorial" by Briggs et al, Chapter 8. The construction of the interpolation operator is given as: Then construction of restriction operator and fine grid operator are given as: Let's assume we have three…
Michael
  • 1,463
  • 11
  • 22
12
votes
1 answer

What is a "hanging node" in the finite element meshing?

When reading literatures about finite element method, the term "hanging nodes" can often be encountered. Could anyone tell me what indeed is a hanging node?
user123
  • 679
  • 1
  • 5
  • 16
12
votes
1 answer

Decomposition methods for solving large optimization problems

I was wondering if anybody had any suggestions for texts or survey articles on decomposition methods (e.g. primal, dual, Dantzig–Wolfe decompositions) for solving large mathematical programming problems. I liked Stephen Boyd's "Notes on…
Amelio Vazquez-Reina
  • 502
  • 3
  • 12
12
votes
4 answers

Making a Molecular editor/visualizer: Object oriented programming, data structures, and molecules

I am new to programming and I am trying to solve my first big problem and write my first big program. I have looked for open source examples of code to learn from, but so far have only found code in languages I don't fully understand or that does…
Nate
  • 223
  • 1
  • 6
12
votes
2 answers

Test of 3rd-order vs 4th-order symplectic integrator with strange result

In my answer to a question on MSE regarding a 2D Hamiltonian physics simulation, I have suggested using a higher-order symplectic integrator. Then I thought it might be a good idea to demonstrate the effects of different time steps on the global…
ccorn
  • 413
  • 5
  • 16
12
votes
0 answers

Are there any standardized file formats for point group character tables?

Character tables are an important tool for symmetry analysis in many computational chemistry software packages. Are there any standardized file formats for point group character tables? This may seem to be an odd question as I could (and I do) just…
jvtrudel
  • 221
  • 1
  • 5
12
votes
2 answers

Verification in Eigenvalue problems

Let us start with a problem of the form $$(\mathcal{L} + k^2) u=0$$ with a set of given boundary conditions (Dirichlet, Neumann, Robin, Periodic, Bloch-Periodic). This corresponds with finding the eigenvalues and eigenvectors for some operator…
nicoguaro
  • 8,500
  • 6
  • 23
  • 49
12
votes
4 answers

What are the best Python packages/interfaces to sparse direct solvers?

Please list the Python package (petsc4py, etc...) and the sparse direct solvers it supports. One (community-wiki) answer per package, please.
ShadowWarrior
  • 213
  • 3
  • 11
1 2 3
…
99 100