# All Questions

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### 3d Ising model simulation - what critical exponents should I be looking for and how do I find them?

For the final project in my computational physics class, I've built and will be presenting results for monte carlo simulations of phase transition in the three dimensional ising model. Using the ...
389 views

### Testing a simple polygon for monotonicity in linear time question

I'm looking for the algorithm of Preparata and Supowit for testing a simple polygon for monotonicity in linear time. I've found it referenced in many textbooks but I can't find the algorithm itself. ...
455 views

### Is there a Moore's law for floating-point precision, and what would it imply?

Moore's law states that the number of transistors on an integrated circuit grow exponentially, roughly doubling at a period of 20 months. This affects the amount of memory available and the speed of ...
1k views

### Are 8 Gauss points required for second order hexahedral finite elements?

Is it possible to get second order accuracy for hexahedral finite elements with fewer than 8 Gauss points without introducing unphysical modes? A single central Gauss point introduces an unphysical ...
5k views

### State of the Mac OS in Scientific Computing and HPC

Back towards the dawn of OS X, there seemed to be a great deal of hubbub, at least in the Mac world (I was nowhere near scientific computing at the time) about the Mac OS as a platform for scientific ...
982 views

### Implementing Euler's method for initial value ODEs

In my physics class, I had to calculate the trajectory of a projectile that was fired (very fast) with $v_0$ in an angle off a planet (radius $R$, mass $M$) from the surface. The projectile would ...
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### Solution oscillations with a small timestep in backward Euler

I am using backward Euler in a FEM scheme for a convection-diffusion problem. On a given mesh, I can take arbitrarily large time steps, as expected. But if I decrease time step, at some point it will ...
341 views

### Where can I find a good reference for the stability properties of several methods of solving parabolic PDEs?

Right now I have a code that uses the Crank-Nicholson algorithm, but I think that I would like to move to a higher-order algorithm for timestepping. I know that the Crank-Nicholson algorithm is stable ...
3k views

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### Nested dissection on regular grid

When solving sparse linear systems using direct factorization methods, the ordering strategy used significantly impacts the fill-in factor of non-zero elements in the factors. One such ordering ...
5k views

### Looking for C/C++ implementations of sampling from multinomial and Dirichlet distributions

I'm looking for C/C++ implementations of functions that return random variates multinomial and Dirichlet distributions. This is in the context of a calculation for posterior predictive p-values, part ...
7k views

### Mathematical Libraries for OpenCL?

I am looking for information from anyone that has tried to use OpenCL in their scientific code. Has anyone tried (recently) ViennaCL? If so, how does it compare to cusp? What about OCLTools? Does it ...
616 views

### Is it possible to dynamically resize a sparse matrix in the Petsc library?

This may be a Petsc newbie question, but... I'm using Petsc to solve a large sparse linear system. The initial creation of the matrix is fairly slow, which I'm given to understand is largely due to ...