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### Schroedinger/Diffusion equation with Crank-Nicolson in Python/SciPy

I tried to make the question as detailed as possible. I have an extremely simple solver written for the Schroedinger equation but with imaginary time, which transforms it basically into the diffusion ...
461 views

### Extracting diagonal of an approximately diagonal matrix when we don't know its entries

What is a good way to extract the diagonal from a symmetric matrix that is already almost diagonal, but where you don't have the matrix elements (only the ability to apply it to vectors)? Further ...
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### Numerically stable explicit solution of small linear system

I have an inhomogeneous linear system $$Ax=b$$ where $A$ is a real $n\times n$ matrix with $n\leq 4$. The nullspace of $A$ is guaranteed to be of zero dimension so the equation has a unique ...
55 views

### Confusion related to convexity of a problem

I was reading this paper related to Multiclass Classiﬁcation with Multi-Prototype Support Vector Machines - paper However, I am having difficulty in understanding why they have mentioned the ...
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### $k$ nearest neighbors for $n$ points with periodic boundary conditions in R^3

Take $n$ points ${\bf r} =\{ r_1 = (x_1,y_1,z_1), r_2=(x_2,y_2,z_2) \ldots r_n=(x_n,y_n,z_n) \}$ enclosed in a periodic box of length $L$, such that that the point $(0,0,0)=(L,0,0)$, $(0,0,0)=(L,L,L)$,...
217 views

### $k$-Nearest Neighbor Search using examples

I want to perform $k$-Nearest Neighbor Search in multidimensional space, but not using for example $L_2$-distance. I want the user to specify some "similar"-pairs examples and then perform a search ...