# Computer Science questions and answers

Computer Science

### What is the naming convention used in ScaLAPACK?

I see that there are many files in the ScaLAPACK library without any immediately obvious naming convention... I'm sure that if the first letter is "p", it means parallel. But I'm not sure how to make sense of the rest of the names as seen here (http://www.netlib.org/scalapack/explore-html/dir_78dd70a4654792622dd59c7dbd6a0c9f.html). .... Nathan: 2 hours ago

Computer Science

I am trying to write a program to compute the advection equation. $$u_t +u_x = 0$$ I use the spectral method for the spatial derivative $u_x$ and the leapfrog method for the time derivative $u_t$. That will give the an equation for the next time step: $$u_{j}^{k+1} = u_{j}^{k-1} - .... Benjamin: 3 hours ago Computer Science ### Definition of Lagrange nodes in Gmsh When gmsh uses higher-order tetrahedral elements, there is an underlying Lagrange basis used to specify the map from reference space to the element. I'm trying to load a gmsh mesh of 3rd degree tetrahedral elements, but I can't seem to find any precise documentation on the location of the nodes .... Charlotte: 4 hours ago Computer Science ### Does the k-th approximate solution of a stationary iteration belong to the k-th Krylov subspace? For an stationary iteration method solving Ax=b as follows:$$ Mx_k = Nx_{k-1}+b, $$I have known that when M = I, i.e., the Richardson iteration, the k-th solution x_k = x_{k-1}+r_{k-1} is in the k-th Krylov subspace K_k(A,b) with x_0=0. So, if we use a Krylov subspace method e.g., .... Harper: 5 hours ago Computer Science ### Periodic Green's functions in integral equation methods in different frequency regimes I'm asking about the solution of the Helmholtz equation on a periodic domain with piecewise constant wavespeed in different frequency regimes. One possible approach is to solving this problem is to write down integral equations on the boundary surfaces in terms of the Green's function of the system. Since the .... Raelynn: 17 hours ago Computer Science ### Is there a complexity between O(n) and O(n \log n) Is there a complexity degree that is bigger than O(n) and smaller than O(n \log n)? .... Jordan: 21 hours ago Computer Science ### Software to build a mesh of a surface from points on the surface I have a set of points (x_i,y_i,u(x_i,y_i))\in\mathbb{R}^3, i=1,\dots N, over a surface S (from experimental data). I need to calculate the integral of a function F over that surface. If the points were points over a volume I could use some mesh software (tetgen, for example) and build a mesh, .... Naomi: 21 hours ago Computer Science ### For which statistical methods are GPUs faster than CPUs? I have just installed a Nvidia GT660 graphic card on my desktop and, after some struggle, I manage to interface it with R. I have been playing with several R packages that use GPUs, especially gputools, and I was comparing the time taken by my GPU and CPU to perform .... Austin: yesterday Computer Science ### scipy optimize fsolve or root I have a function: delt=1 #trial def f(z): return ((1-2*z)*np.exp(-delt/z))/(((1-z)**(2+delt))*(z**(2-delt))) I also have a variable: import scipy.integrate as integrate var=integrate.quad(f,0,0.5) # equals 0.040353419593637516 Now I am trying to find the value p such that integrate.quad(f,0.5,p)= var and manually I can check that it is around 0.605 I define the following .... Elizabeth: 2 days ago Computer Science ### adaptive Gauss-Kronrod quadrature with vector-valued integrand So I'm trying to implement a Gauss-Kronrod adaptive quadrature. That is, I want to calculate$$\int_a^b f(x) dx = \sum_i f(x_i) w_i where f(x) is evaluated at multiple points at once for efficiency. A key point to bear in mind is that $f$ is also vector-valued (possible risk of confusion .... Stella: 2 days ago