Questions tagged [grid]

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gnuplot splot command analog in Paraview

I would like to plot the points contained in this file with Paraview, but can't seem to figure out how to do so. Each column in this file corresponds to a set of 2048 points on a 64x32 grid. Each ...
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1answer
43 views

Is it possible to resample grid in such a way so that continuous objects remain continuous?

Suppose I rasterize a rectangle of width 2.5 gridpoints and get the values as shown: =============== | 0 | 1 | 1 | 0.5 | 0 | Now I resample that ...
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23 views

Solution errors when refining a static grid: Continuous vs. step-wise refinement

Let's assume I am working on a 2-D domain on $R^2$, with my coordinates $x \in[-1,1]$, $y \in[-1,1]$ and I want to solve a popular CFD problem, like the shallow water system or the Euler system. At $x=...
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32 views

Grids for atmosphere simulation with finite volumes on the globe

I am currently in the early construction process of building a simple CFD model of a rotating planetary atmosphere. The planet should be allowed to tilt significantly, so that a time-dependent source ...
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1answer
87 views

Good C, C++ library for efficient grid search / tuples, ideally with bindings to Eigen

I have a $q$-dimensional grid, known at run, not compile-time, that has $50$ points in each direction and hence $50^3$ combinations that I would like to first build and then call a function with each ...
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17 views

Translating grid with extrusion speed

I am putting into MATLAB code the equations that describe a plastic extrusion process. From a paper, I found I should use a spatial grid that translates with the extrusion speed, being the reference ...
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97 views

WENO5 scheme in a staggered grid

I'm trying to use the finite-difference WENO scheme to solve the 2D density conservation law with axial symmetry (coordinates $r,z$): $\frac{\partial \rho}{\partial t}+\nabla \cdot (\rho \vec{v}) = \...
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1answer
151 views

Mapping derivative information in uniform to non-uniform grid

I'm having two sets of grids. One is uniform and another one is not uniform. I will calculate the derivative in uniform grid points and I like to transfer(map) the derivative to the non-uniform grid ...
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1answer
84 views

Grid dependence of a numerical model

Statement of the problem Suppose, we consider the following model $$ \begin{array}{l} (1)~\mathbf{u}_t + \mathbf{F(u)}_x = \mathbf{S}(\mathbf{u},\mathbf{w}), \\ (2)~\mathbf{w}_x = \mathbf{P}(\mathbf{...
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2answers
62 views

Access optimized data structure for representing integer lattice

Consider the integer lattice in $2d$, namely the set $\mathbb{Z}^2 = \{(x,y): x,y\in \mathbb{Z}\}$, and let $u:\mathbb{Z}^2 \to \mathbb{R} $ be a function defined on some bounded subset of $\mathbb{Z}^...
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1answer
993 views

Three dimensional irregular grid data interpolation to regular grid

I have three-dimensional radar reflectivity data obtained as voxels (scans, rays, altitudes). The data has been sampled at irregular spacings and I want to convert this into a regular grid. In ...
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1answer
34 views

Converting mass density to point mass approximation on a grid

In an nbody gravity simulation, instead of doing exact(all-pair brute force) solution, I added masses of each body into cells of a 3D grid(each cell is just a float value having a mass value). Then ...
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84 views

Choice of velocity grid - staggered or not?

I'm trying to understand when and why one would use a staggered vs. a colocated grid in problems that have velocities and scalars that they transport (e.e. density). If scalars are defined cell-...
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55 views

adaptive / smart grid choice for dynamic programming

I've a read a paper about investing where they used a dynamic programming approach to solve a finite horizon problem, i.e. $$\max_{x_t} E[u(W_T)] $$ where $u$ is a utility function and $W_T$ ...
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2answers
146 views

Grid mapping from Tchebyshev

I am using Tchebyshev discretization to solve a system of PDEs. Usually, I map the Tchebyshev space($\xi$, from -1 to 1) to physical space ($x$, from 0 to L) using $$x = (\xi +1)*L/2$$ Now, I also ...
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2answers
62 views

Efficient Representation of (spatially sparse) spatial time series

Background I have a huge dataset consisting of points (on a plane) together with a timestamp for each point. This is a collection of car GPS measures, giving us the location (latitude/longitude) of ...
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1answer
46 views

Balancing core load when number of particles in cells vary (PIC on GPU)

Consider this basic scheme for particle in cell simulations ( with just short-range interactions ): assign particles to disjunct cells for cell $A$ go over neighboring cells $B$ for each particle $...
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1answer
281 views

Finite Volume Polar Discretization: Lengths

Given a uniform polar grid, as in the figure below: and a FV discretization of a gradient for example: $\frac{\partial p}{\partial \varphi} = 0$ $\Delta r \frac{p_e - p_w}{\Delta \varphi} = 0$ My ...
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151 views

How to optimally choose points for multivariable Hermite interpolation?

I have a multi-variate, continuous function $f$ from $R^n$ to $R$, which I can query for its output for any input. I would like to create interpolation polynomial for it. In one-dimensional case ...
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2answers
537 views

Finite Difference Grid Spacing and Scaling

I have been exploring finite differences and heat transfer using the 2D heat equation to further expand my knowledge. So far I think it is going well. I am running into some confusion around grid ...
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1answer
2k views

Is there an advantage of using a staggered grid over a regular one when combined with high order methods?

The title says is all. This question is in the contest of an incompressible Navier-Stokes solver. Specifically, I am currently working on a new solver while referring myself to an older code for ...
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1answer
497 views

Interpolation of velocities on staggered grid (in PIC)

Edit: (copying from my comment) Let's consider the inverse problem when I need to transfer velocities from particles to the grid (inverse bilinear interpolation). How'd I transfer a particle's x-...
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0answers
125 views

C1 continuous spline on regular 2D-grid with quadratic 1D cuts

I want some scalar spline function defined on regular 2D grid $F(x,y)$ with continuous first derivative which is easy to intersect with arbitrary ray/line ${\vec l}(t) = (c_x t,c_y t,c_z t)$. ...
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1answer
112 views

Alternative to messy grid node indexing within multiple layers of loops

Recently,I dive into a set of somehow ancient Fortran codes and try to fully understand them. A large fraction of these codes are multiple layers of loops over many state variable dimensions, which ...
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1answer
387 views

3-dimensional plotting with nonuniform grids

I have 3 variables I am considering: time (t), 1-dimensional space (x), and intensity (I). I would like to plot the intensity in the z-axis as a function of t and x (the latter two variables would ...
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1answer
2k views

Contour plot interpolation recommendation

I am not sure if my question is on topic or not and if not please let me know. I have regularly spaced gridded data(output of a weather forecast simulation software) and I have latitude and ...
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0answers
118 views

Finding boundary intersection points with Cartesian grid?

I would like to find the intersection points e.g. $M_x$ and $M_y$ as in the attached figure. The boundary (solid line) is defined by the Lagrangian points. I am working in C++ (basic - medium ...
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1answer
82 views

Common nodes in two FEM grids

There are two independent tetrahedral FEM grids. Second grid is subset of the first. By subset, I mean: nodes from the second grid are exactly in the same positions as some nodes from the first grid. ...
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1answer
656 views

Generating a non-uniform grid

I am interested in generating a 1D non-uniform grid on the interval [0, L] with N points, where a region of width $\sigma$ and ...
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1answer
838 views

Quadtree type Grid

I would like to code for a quadtree type meshing but don't know how to do. If anyone can help or can share any starting code?
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5answers
6k views

Dynamically ending ODE integration in SciPy

I have a light ray moving through space-time, i.e. a curve in R⁴, parametrized by some variable λ. The exact trajectory, i.e. the coordinate functions $x^μ(λ)$ of the curve are given by some ODE $\...
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1answer
57 views

Should I use bestman2 or dcache CLIs (srmping, srmls, etc..)

I am fairly new to using SRM, and I am wondering if I should be using srm CLI tools (srmping, srmls, srmcp, etc..) provided by dcache, or bestman2 counter parts (srm-ping, srm-ls). I used to think ...
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1answer
244 views

How to compute the weight matrix for tomography applications?

I am trying to compute the weight matrix for a set of straight ray paths through a reconstruction region. Ideally, I would like to be able to do this for both a rectangular grid region, where each ...
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1answer
34 views

How can I discover / access various SE (storage elements) in GlideinWMS environment?

I am submitting jobs to Open Science Grid from a glidein-wms enabled submit hosts such as osg-xsede. I'd like to stage some data on SE nearest to osg-xsede submit host, then distribute data to various ...
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1answer
2k views

Python: Grid with step control ODE solver

I have a problem in physics formulated via an ODE. Now I like to solve it numerically using Pythons scipy.integrate and the therein complex_ode. I figured out how and it works but now I like to ...
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1answer
290 views

Ray tracer : create an uniform grid [closed]

I wrote a simple ray tracer, and now I try to implement an uniform grid. There is a lot of documentation on how to traverse the grid, but I don't know how to construct the grid. I have my uniform ...
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1answer
126 views

How to convert a Matrix to a DistMatrix in Elemental?

I have a Matrix<double> on a single core, the result of doing an MPI_Reduce. I want to do the Cholesky, so I need to ...
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1answer
51 views

Cells segregation

There is unstructured grid which contains only quadrangles cells. Each cell has 4 neighbors, and known them (has a pointer to them). I can iterate through all cells in the grid. Some cells are marked ...