Top new questions this week:
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For stable time steps for the RKDG method for transport equations we require that
$$
\Delta t \le \frac{\Delta x CFL}{(2k + 1)|\lambda|},
$$
where $\lambda$ is the eigenvalue of our conservation law ...
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Given an $m \times n$ matrix $A$ and a vector $x\in\mathbb R^n$, with $m<n$, what's an efficient way of computing the projection of $x$ onto the kernel of $A$?
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I'm trying to figure out how to create a surface mesh from a set of labeled 3D points. The 3D object could be something like part of a cave system or asteroid where there would be parts of the surface ...
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I have a saddle-point system of the form
\begin{equation}
\begin{bmatrix}
A & B \\
B^T & O
\end{bmatrix}\begin{bmatrix}
x\\
y
\end{bmatrix} = \begin{bmatrix}
f \\ \vec{0}
\end{bmatrix},
...
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Greatest hits from previous weeks:
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$A$ and $B$ are $n \times n$ matrices and $v$ is a vector with $n$ elements. $Av$ has $\approx 2n^2$ flops and $A+B$ has $n^2$ flops. Following this logic, $(A+B)v$ should be faster than $Av+Bv$.
...
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I would like to perform a PCA on a dataset composed of approximately 40 000 samples, each sample displaying about 10 000 features.
Using Matlab princomp function consistently takes over half an hour ...
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EDIT: I am testing if any eigenvalues have a magnitude of one or greater.
I need to find the largest absolute eigenvalue of a large sparse, non-symmetric matrix.
I have been using R's eigen() ...
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Thomas algorithm can be used to solve a tridiagonal matrix:
$$
\begin{bmatrix}
{b_ 1} & {c_ 1} & { } & { } & { 0 } \\
{a_ 2} & {b_ 2} & {c_ 2} & { } & { ...
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I was very surprised when I started to read something about non-convex optimization in general and I saw statements like this:
Many practical problems of importance are non-convex, and most
...
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Is there a Fortran subroutine which performs linear interpolation in one-dimenional data?
I need something similar to MATLAB function interp1.
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I work in computational science, and as a result, I spend a non-trivial amount of my time trying to increase the scientific throughput of many codes, as well as understanding the efficiency of these ...
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