# All Questions

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### Python import Data from .txt. file with pandas down from a specific line

I am really new in Python and I hope this is the right community for my question. Sorry if it is not. I am trying to import data from a .txt file with pandas. The file looks like this: ...
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### Sparse Matrix Matrix multiplication using Intel MKL

Let $D$ be a sparse matrix. I want to compute $D\times D^T$. As $D$ is fairly large, so I am row-slicing $D$. That means for a range $(i,j)$, I am computing $C = D(i:j,:) \times D^T$ and performing ...
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### How to extract text from several .json files and put all of them in a single file? [closed]

I have a bunch of .json files, say 1000. To read each files I run the following code in MATLAB fname = 'C:\Users...\d90f3c62681e.json'; val = jsondecode(fileread(fname)); the output is as follows. <...
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### integrate.solve_ivp bugged

I am trying to solve an ODE with solve_ivp, but I am getting strange errors. Documentation: https://docs.scipy.org/doc/scipy/reference/generated/scipy.integrate.solve_ivp.html ...
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### Numerical flux and source term in FVM (Burger's like equation)

I'm trying to solve the following equation with FVM $$u_t + f(u)_x = g(u)$$ where $g$ is some smooth function of $u$ and $f(u) = \frac{u^2}{2}$. This is really similar to Burger's equation, except ...
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### Detecting degenerate triangles with very thin structures

Between the two ears in the following bunny images, there are some degenerate triangles I want to detect. It looks like a volume-less thin slits. If the question is not clear, please let me know.
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### Why addCylinder function not respecting the given coordinates?

I tried to generate 3 very simple cylinders, each other connected to it end, however the cylinder get connected to an unexistent point in space as the image shows: It was supposed to each segment be ...
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### Generating Random Orthogonal Matrices in C++

I'm looking for an open-source library for the generation of random n-dimensional orthogonal matrices in C++. In python, it looks like such a function is available in the NumPy package. But I was not ...
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### Numpys tensordot and what is happening mathematically

I've encountered a program where np.tensordot was used, so I tried looking it up but I can't really understand what this function is doing... I feel rather ...
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### Is C++ and Object-Oriented Numeric Computing for Scientists and Engineers by Daoqi Yang still relevant?

I'm looking to learn C++ primarily from a scientific computation perspective. The approach of the textbook seems ideal to me as it covers C++ from first principles with an emphasis on numerical ...
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### Sparse matrix-matrix multiplication using AVX2

I have two sparse general matrices stored in CSR format I need to multiply. Is there any chance to gain performance using AVX2? In general the matrices are big (hundreds of millions of non-zeros and ...
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### How to detect fraud rows given possible states? [closed]

Suppose we have a database with attributes Player_ID, Source_of_app, Post_install_activity. Post_install_activity includes 4 possible actions (e.g. "install", "lvl_reached_3", "lvl_reached_5", "...
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### MInimizing cost function using iterative search for a minimum method

I want to estimated the parameters $\ \hat{\theta}$ of a model using an iterative search for the minimum of a cost function. The cost function is defined as follows:  V_N(\hat{\theta}) = \frac{1}{...
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### Computing node, cell and face incidence in 3D structured meshes

I'm developing a PDE discretization algorithm that works on 3D uniform structured meshes. For this algorithm, I often have to traverse the mesh nodes and get the ids of all the faces and all the cells ...