# All Questions

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### Using PAPI in PETSc code

I am trying to count the number of cache misses, total cycles, etc. per iteration of a for loop inside MatMult_SeqSBAIJ_2() . I'...
2answers
211 views

### Re-scaling array of floats so that all items are approximately integer

I have an array of floating point values $F$. I want to input my array into an algorithm that only takes integer values. How can I efficiently determine the smallest multiplier $m$ such that all ...
2answers
524 views

### Numerical method for equation solving that works on stochastically computed functions

There are many well known numerical methods for solving equations of the type $$f(x) = 0, \quad x \in \mathbb{R}^n,$$ e.g. bisection method, Newton's method, etc. In my application $f(x)$ is ...
1answer
76 views

### a posteriori error estimation for skewed elements

I'm working with error estimates for Poisson's equation of the form $$\mathcal{E}^2_T = h_T^2\|-\Delta u - f\|_{L^2(T)} + \sum_{e\in \partial T} h_e\|n\cdot \nabla u\|_{L^2(e)}$$ where $T$ is an ...
1answer
259 views

### Multigrid stops converging when more grid levels are used

I'm having a problem with multigrid code I wrote. If I solve Laplace's equation in 2D and use more than 5 grid levels, the V-cycles stop converging after a few cycles (see below, convergence factor > ...
1answer
915 views

1answer
129 views

### combine $n$ vectors using $L2-normalization$

Suppose that I have the following vectors $v_1$, $v_2$, $v_3$ $\in R^n$,$n= 9$. What I want to do exactly is to combine these $3$ vectors into $1$ representative vector $V$. According to the ...
1answer
887 views

### Scientific computing with Python with modern GPUs with double precision

Has anyone here used double precision scientific computing with new generation (e.g. K20) GPUs through Python? I know that this technology is rapidly evolving, but what is the best way to do this ...
0answers
209 views

1answer
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1answer
391 views

### PETSc input format for linear solvers

I’m going through some considerable effort to translate one of my codes from MATLAB. It’s a type of finite element code and I haven’t implemented the solver yet but comparing CPU times for simply ...

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