# Computational Science Stack Exchange Community Digest

## Top new questions this week:

### Time Integrators for Water Wave Simulation

I am interested in using a numerical wave tank (NWT) to study the performance of various water wave dampers using MATLAB. I am looking at nonlinear water waves. My current NWT (2d, periodic) is based ...

nonlinear-equations time-integration
 asked by Gary Moon Score of 2
 answered by David Ketcheson Score of 2

### A question on the Poisson equation with Neumann and periodic boundary conditions on a rectangular region

I am trying to solve the following PDE by using finite difference \begin{eqnarray*} \Delta u&=& f ~~on~~(0,1)\times(0,1)\\ \frac{\partial u}{\partial y}(x,0)&=&0=\frac{\partial u}{\...

finite-difference numerics poisson
 asked by User124356 Score of 1
 answered by Maxim Umansky Score of 1

### stability of a numercial scheme for a hyperbolic system?

This is related to my question here https://math.stackexchange.com/questions/4447383/lax-wendroff-scheme-stability-analysis-for-a-linear-system-of-conservation-laws . Consider the numerical scheme ...

stability hyperbolic-pde wave-propagation
 asked by NotaChoice Score of 1
 answered by Philip Roe Score of 5

### Accurately solving system of differential equations

So I am trying to solve two equations simultaneously. The goal is to find values for $\frac{de}{dt}$ and $\frac{d}{dt}$ which are the rates of change of the variables $a$ and $e$. I am then ...

ode numerical-modelling differential-equations
 asked by Peter Smith Score of 1
 answered by Wrzlprmft Score of 2

### Efficiency of developing PDE solvers using sparse matrices versus loops

I am new to solving PDEs, but have been looking at different implementations of finite difference and finite volume schemes. One thing I have noticed in different implementations is that some ...

pde numerics sparse-matrix efficiency
 asked by krishnab Score of 1

## Greatest hits from previous weeks:

### How to discretize the advection equation using the Crank-Nicolson method?

The advection equation needs to be discretized in order to be used for the Crank-Nicolson method. Can someone show me how to do that?

pde advection crank-nicolson
 asked by pandoragami Score of 8
 answered by boyfarrell Score of 20

### What's the fastest software(open source) to solve mixed integer programming problem

I have a mixed integer programming problem. And I am current using GLPK as my solver. But I found that GLPK is good for Linear Programming problem, but for Mixed Integer programming, it requires much ...

optimization software linear-programming mixed-integer-programming
 asked by Yu Hao Score of 18
 answered by Geoff Oxberry Score of 17

### How mature is the "Julia" scientific computing language project?

I'm considering learning a new language to use for numerical/simulation modelling projects, as a (partial) replacement for the C++ and Python that I currently use. I came across Julia, which sounds ...

parallel-computing languages julia
 asked by N. Virgo Score of 61
 answered by Chris Rackauckas Score of 58

### What are some good strategies to test a floating point arithmetic implementation for double numbers?

For IEEE, the single representation is 1-bit sign, 8-bit exponent and 23-bit mantissa. This means that at each exponent value, you can test all 2^23-1 (roughly 9mil cases) possible combination of ...

floating-point testing
 asked by Quang Thinh Ha Score of 16
 answered by Richard Score of 20

### How much more work is it to code math models in Python, compared to working with Matlab?

If one had to code up a new dynamical system for a research group at a university, and the university has a Matlab total headcount license so that one could code in Matlab, are there any benefits to ...

matlab python career-development
 asked by user33708 Score of 11

According to Nocedal & Wright's Book Numerical Optimization (2006), the Wolfe's conditions for an inexact line search are, for a descent direction $p$, Sufficient Decrease: $f(x+\alpha p)\le f(x)+... optimization  asked by Paul Score of 14  answered by Wolfgang Bangerth Score of 14 ### How do I take the FFT of unevenly spaced data? The Fast Fourier Transform algorithm computes a Fourier decomposition under the assumption that its input points are equally spaced in the time domain,$t_k = kT\$. What if they're not? Is there ...

fourier-analysis
 asked by David Z Score of 68
 answered by Jack Poulson Score of 48
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