# Tag Info

## Hot answers tagged python

### How to solve a second order differential equation (diffusion) with boundary conditions using Python

I have found that I must keep the value of dt near dx or the results become unstable This behavior you have noticed is known as the Courant–Friedrichs–Lewy (CFL) condition. Indeed, there are ...
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### Python: Underflow vs. exp of large negative numbers

If your final result is of the order of magnitude of exp(-1000) $\approx 5 \cdot 10^{-435}$, then you are out of luck; no matter how you compute it, it will always ...
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### Why Is This Python Code Faster Than Fortran Wrapper with F2PY?

Shoutout to Kyle Mandli and Endulum who each contributed to this answer in the comments. First, I took Endulum's suggestion and removed the redundant reshapes. ...
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### Why is my curve_fit not producing the covariance matrix and the correct values for the unknown variables?

The problem seems to be one of scaling. When I added the jacobian of the function an overflow warning appeared. Thus, I divided the data by their maximum values and it worked. Following is the code. <...
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### Going to try to move some of my scipy/numpy calculation to a new GPU, how to avoid disappointing results?

I buy the wrong CUDA GPU and the speed up is minimal or nonexistent. It is highly unlikely that your choice of GPU will have a significant impact on your speed-up unless your model is very big. To a ...
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### Calculate determinant of unitary matrices based on SVD implementation

If you are prepared to go digging around in the fortran code: The SVD algorithm consists of a few parts: Bidiagonalization (usually using Householder reflectors) Use QR shifts to reduce the ...
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### Is there any way/any python function to calculate the condition number of the roots of a polynomial directly?

The condition number of a root $r$ of a polynomial $p$ is $$\kappa := \frac{\left\| p \right\|}{|rp'(r)|}$$ There is some arbitrariness in the choice of norm which affects the definition of the ...
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### Is there something unique you can get out of a set of numbers?

One simple way to do this is with a product of powers of primes. Let the hash function be $f(x_{1},x_{2},\ldots,x_{n})=2^{x_{1}}3^{x_{2}}\cdot p_{n}^{x_{n}}$ where $p_{n}$ is the $n$th prime number. ...
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### Why do problems arise in FFT for smaller value of df in Python?

The discrete Fourier transform for a signal of period $T$ with $N$ samples reads in its inverse or reconstruction form as $$y(t)=\frac1{N}\sum_{k=-N/2}^{N/2}c_k e^{i2\pi k\frac{t}{T}}$$ with ...
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### How to solve the integral-like energy equation with Sagdeev potential numerically in Python?

A simple approach here would be to use the shooting method, by integrating from $\xi$=0 to infinity (some large value) the ODE written as $\frac{d}{d\xi} \phi = \sqrt{-2 S(\phi)}$ Due to the ...
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### Single hexahedral element stiffness matrix problem, help me find the mistake

Your intuition is right, the stiffness matrix should be singular. Actually, as pointed by @BillGreene, it has an eigenvalue that is zero. Ordering the nodes as follows (-1, -1, -1,), (1, -1, -1), (1, ...
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