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1500 questions
7
votes
1 answer
Does some form of documentation of GMSH exist?
I am looking to implement GMSh into a simualtor that I am going to create. I am looking to integrate the geo, mesh, and post processor modules.
However, looking online, it appears the documentation for the GMSH function calls are non existent. I was…
philm
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7
votes
2 answers
is accessing an element in an array slower than accessing a variable?
when optimizing my code, i find myself often writing something like the following ...
do i = 1,n
r = t(i)
y(i) = r*r*2.0
f(i) = r*3.5
enddo
what i am doing with my variable, r is really irrelavent except that it is used more than once,…
drjrm3
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7
votes
1 answer
Approximation properties of FEM projections operators on a boundary
We have an elliptic projection
$$P: V \rightarrow V_{h}$$
which satisfies
$$\Vert u - Pu \Vert_{L^{2}(\Omega_{e})} \leq Ch^{k+1} \enspace .$$
Can we say anything about $\Vert u - Pu \Vert_{L^{2}( \partial \Omega_{e})}$?
I know if we have use the…
Mike Harmon
- 71
- 2
7
votes
1 answer
Alternative to Bron-Kerbosch algorithm for enumerating maximal cliques in inverse interval graphs
I often use inverse interval graphs to represent biologically relevant features along a genomic sequence. For example, given a (relatively) small genomic region, the graph would contain a node for each gene in the region, and there would be an edge…
Daniel Standage
- 663
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7
votes
3 answers
What is the best high performance computing platform for engineering simulations?
What is the best platform for high performance computing (HPC)?
Windows is long gone, I think. So only Unix and Linux stand the chance. What platform will strongly back my interest on computational mechanics?
The application field is large dynamic…
ShadowWarrior
- 213
- 3
- 11
7
votes
2 answers
Learning parameters of noise and filter coefficients from data where data and noise both have Gaussian distributions
Assume $X$ and $N$ are two sets of vectors (observations) from two different normal distributions, where $X$ represents clean data and $N$ represents noise; and $A$ a projection matrix of a filter. the scenario is that our clean data was corrupted…
PickleRick
- 195
- 6
7
votes
4 answers
Plot integral function with scipy and matplotlib
I want to plot a numerical integral function of some function $f$ using scipy and matplotlib. How can I do this?
I tried the following but it didn't work (run with ipython %pylab):
import numpy as np
from scipy import integrate
def f(x):
return…
student
- 231
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7
votes
1 answer
Fourth order IMEX Runge-Kutta method
I am looking for the Butcher tableau of a fourth order accurate Runge-Kutta method with IMEX splitting. I have been reading the ''classical'' paper on the subject by Ascher, Ruuth and Spiteri as well as a number of works that cite this paper…
Daniel
- 1,273
- 10
- 22
7
votes
3 answers
How to compute the rank of a large sparse matrix in MATLAB
I am interested in computing the ranks of fairly large, the largest being of magnitude $10^6$ x $10^6$, sparse matrices whose entires are all 0, 1, or -1. I have been trying to use Matlab to accomplish this. In particular, my approach has been to…
jemmy.bruce
- 171
- 4
7
votes
1 answer
Solving a simple Schroedinger equation with Fast Fourier Transforms
While trying to solve a stochastic Gross-Piaevskii equation I have found a problem that can be tracked down to something buggy occuring in the simplest Schrodinger equation possible:
$\partial_t \psi = i \partial^2_x \psi$
This has the very simple…
Carlos_San
- 71
- 1
7
votes
1 answer
Numerical computation of Perron-Frobenius eigenvector
I would like to efficiently and (to the extent possible) reliably find the Perron-Frobenius eigenvector of non-negative matrices. These are not stochastic matrices, they are typically dense, and their entries differ by many orders of magnitude. They…
N. Virgo
- 1,223
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7
votes
4 answers
Are there any general fluid dynamics frameworks?
Are there any frameworks that could be classified as "general computational fluid dynamics framework"?
What I'm thinking of is a framework that's modular and extensible in order to allow the development of new algorithms pretty much unlimitedly. And…
mavavilj
- 427
- 2
- 8
7
votes
3 answers
Reconstructing a continuous function from finite element method. Is there a faster algorithm for doing so?
Lets say I've decomposed a continuous function $y(x)$ over some domain $L_x$ using known finite element method with local basis $Q_i(x)$. Suppose $L$ is divided into $M$ "elements". If I want to know the function $y(x)$ at a point $x=p$ (where $p$…
user2350366
- 191
- 2
7
votes
1 answer
Solving an ODE beyond existence. What's happening?
As an example for an ODE course I used the ODE
$$
y' = \frac{y}{x} + \frac{1}{\cos(\tfrac{y}{x})}
$$
to illustrate domains of existence. Standard substitution $z=y/x$ turns the equation to
$$
z' = \frac{1}{x\cos(z)}
$$
which can be solved by…
Dirk
- 1,738
- 10
- 22
7
votes
1 answer
Which preconditioning for large linear elasticity problem?
The problem I want to solve is the displacement formulation of the linear elasticity :
$$
\nabla \cdot \sigma = 0 \quad \text{in} \quad \Omega \\
\sigma = \lambda ( \nabla \cdot u ) I + \mu (\nabla \cdot u + \nabla \cdot u^t) \quad \text{in} \quad…
maxence5694
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