# All Questions

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### Correctly orthogonalizing and normalizing eigenvectors of a non-hermitian problem

I have some non-hermitian matrix $A$, that I have the left and right eigenvectors. (Calculated using SLEPc, by finding the eigenvectors of $A$ and $A^H$). I'm not sure how to orthogonalize them ...
27 views

### Level 3 BLAS accelerated solver for banded linear systems.

At the moment I consider the following problem. I have a huge dense banded matrix $A$ which I want to factorize and use to solve linear systems $Ax=b$. $b$ has around more than 100 columns. At the ...
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### Why is Matlab's SVD faster on think matrices than on wide matrices?

I noticed something odd today. I have a matrix X that is very skinny (20800 x 200), double precision real numbers, not sparse, ...
60 views

### Incremental SVD implementation in MATLAB

Is there any library/toolbox which has implementation of incremental SVD in MATLAB. I have implemented this paper, it is fast but does not work well. I tried this but in this also error propagates ...
48 views

### Looking for open source numercial solver

I am trying to solve an optimization problem $min f(x)$ subject to $Ax\leq b$ with both $x \in R^{\sim 10000}$ and $b \in R^{\sim 10000}$. $A$ is somewhat sparse (usually less than 5% populated) and ...
37 views

### parallel computatioan of a PDE in MATLAB

I want to solve a 1-D PDE $(\partial_{tt} + \alpha\partial_t)u(x,t)=\partial_{xx}u(x,t)-\sin(u(x,t))+f$, using method of lines and for this I defined a spatial grid of about n~1000 points. Since my ...
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### How to project a vector into the H(div) space (in the context of finite elements)?

Say I have a simple elliptic PDE: $$-\nabla\cdot(K\nabla p) = f \;\;\;\text{in}\;\Omega$$ with the appropriate boundary conditions. I solve for $p$ using a FEM (a discontinuous Galerkin method to ...
16 views

### wilcoxon signed rank test [on hold]

Is it correct to test a data set of as low as 5 for a wilcoxon signed rank test for a significance value of 7%? Currently I'm using MATLAB for this test and I am getting a p=0.0625. Can I be assure ...
10 views

### Fit model to transfer function using different frequency resolutions

I am not certain if I should post this here or maybe on another stackexchange site such as signal processing, however because this is about fitting a model on to a transfer function and not on how to ...
67 views

### Penalty Formulation for elliptic PDE [on hold]

Penalty methods are applied to elliptic PDEs with complex/irregular domain. Given a Dirichlet problem of the form: find $u\in{H^1}(\Omega)$ so that $$-\Delta{u}+u=f\;\;\mbox{in}\;\Omega$$ ...
48 views

### beta in Nesterov's first method for piece wise linear convex optimization problem

I am trying to implement Nesterov's first method to solve convex piece-wise linear optimization problem, from this website: ...
19 views

### Abaqus changing the orientation [closed]

in Abaqus, *ORIENTATION,NAME=RECT,SYSTEM=RECTANGULAR 1.0, 0.0, 0.0, 1.0, 1.0, 0.0,0.0,0.0,0.0 **** i would like to change the orientation of the composite ...
843 views

### How can calculations cause an arithmetic overflow even if the final value fits?

I am reading Algorithm Design Manual by Skiena, which says in Chapter 8, Section 8.1.4 when talking about the calculation of binomial coefficients: Intermediate calculations can easily cause ...
92 views

### Compute eigenvectors of a matrix with known eigenvalue spectrum

If I have already accurately known the eigenvalue spectrum (i.e. all eigenvalues) of a matrix, is there any efficient numerical algorithm to compute all the eigenvectors corresponding to these ...
66 views

### Already exist? parallel computing [closed]

Parallel computing allow us to compute tasks in parallel. And if there was a system like torrent that unlike sharing files, it share computing power? For example I have a gpu and I use only 25% of its ...
30 views

### Cross platform GPU computation for real time ray tracing rendering engine! [closed]

As optix - https://developer.nvidia.com/optix is real time ray tracing rendering engine but it only works on CUDA, I want to implement real time ray tracing engine for games like which will work on ...