All Questions

0
votes
0answers
5 views

state of art MAX-SAT solver for ising spin glass

What is the best MAX-SAT solver problems for Ising spin glass? I tried Scip-Max-sat and open-wbo. While open-wbo cannot solve the instance with only 27 variable Scip-max-Sat fail to solve the one with ...
4
votes
0answers
10 views

Evaluating oscillatory integrals with many independent periods and no closed forms

Most methods for oscillatory integrals I know about deal with integrals of the form $$ \int f(x)e^{i\omega x}\,dx $$ where $\omega$ is large. If I have an integral of the form $$ \int ...
0
votes
1answer
9 views

Code/package for Quasiharmonic approximation

I'm trying to find some finite temperature properties using ab-initio simulations; and for this, I'm looking for a tool to be used as an auxiliary to DFT simulations (in VASP) to implement ...
1
vote
0answers
16 views

Infinite Function Value on Dirichlet Boundary

I have been working on a multigrid solution to a non-homogeneous Dirichlet boundary value problem. However, the function goes to infinity on the boundary. This causes numerical overflow errors to be ...
1
vote
0answers
33 views

Splitting Operator

I have a problem with this finite element formulation. After applied a Splitting Operator $Q=\hat{Q} + \tilde{Q}$ I do not know how to procede. I need to obtain the solution of the following finite ...
4
votes
1answer
78 views

How does the L-stability or A-stability of a scheme reflect on its ability to preserve an invariant?

I am working with the simple example of an oscillator: $$(1) \; \; \ddot{u} + u = 0, \; \; u(0) = u_0$$ I know that Forward Euler does not preserve an invariant of the above system: $$(2) \; \; ...
2
votes
0answers
33 views

4th order tensor [on hold]

I'm new with FEniCS and Python and I'm stuck with this issue: is there a way to write a 4th order tensor in an easy way to implement? I have to compute the following stiffnes tensor: $A_{ijkl}= ...
0
votes
0answers
9 views

MAX-SAT pseudo-boolean optimization(PBO) weighted boolean optimization(WBO) solver

I have come across (state of the art) softwares on MAX-SAT PBO or WBO: examples are WBO, open-WBO, SAT4J, scip. They all seem to work in a way that only command line instruction is involved. I want to ...
3
votes
1answer
43 views

When should a geometric stiffness matrix for truss elements include axial terms?

Bathe's Finite Element Procedures shows the "nonlinear strain stiffness matrix" for a 2D truss element as $$ \frac {^tP} {L_0 + \Delta L} \left[ \begin{array}{ccc} 1 & 0 & -1 & 0 \\ 0 ...
1
vote
0answers
22 views

numerical solver for stochastic optimal control problems

can any one recommend numerical solver (c/c++ library preferred) for stochastic optimal control problems? For deterministic optimal control I found something like that: ...
3
votes
2answers
30 views

Optimal solution to a table of numbers

I want to maximise the score of the following table, choosing one item from each column/row, so no two items are on the same row or column. Score to maximise is just adding all the choices together. ...
1
vote
1answer
37 views

What are the good testing problems for hyperbolic equation?

I read the whole list of this question: Where can one obtain good data sets/test problems for testing algorithms/routines? But the answers are in different areas and I want to ask a specific area. I ...
2
votes
2answers
43 views

Adaptive mesh refinement algorithms and the difference between AMR and moving mesh

I'm working on my thesis and a part of it has to do with adaptive mesh refinement. As a computer science major, I'm not too familiar with this field. The best way I can put my knowledge of AMR is: I ...
0
votes
0answers
31 views

Prove $NuclearNorm(W*U*S)\geq NuclearNorm(W*S)$ [migrated]

Suppose $W$, $S$ is two diagonal matrices of size $n*n$. $U$ is an orthogonal matrix. For $W$, the diagonal elements satisfies: $0\leq w_{1,1}\leq w_{2,2}\leq ...\leq w_{n,n}$, and for $S$, the ...
4
votes
1answer
60 views

Evaluate sine of a polynomial root close to $\pi$

Consider the polynomial $$ p(x) = -514-462 x+359 x^2+1129 x^3+165 x^4+490 x^5-418 x^6+497 x^7-227 x^8+60 x^9-10 x^{10}, $$ whose root $A\approx 3.14$ is very close to $\pi$: $$|A-\pi|=2.0746\times ...
0
votes
1answer
71 views

Statistical analysis of optimization algorithms

If we optimize some parameter using 4 optimization algorithms, 2 of which are population based (say A and B) and 2 trajectory methods (single point search)(say C and D); what statistical test can be ...
3
votes
2answers
125 views

Programming Finite Element Methods in C++

I am trying to develop a library for finite element methods in C++ and for that I am looking at the data structures for meshes. Based on what I've read up on fenics and deal.ii, the general ...
6
votes
2answers
288 views

A method to determine whether a point can be contained within a circle with no neighbouring points

I have been working on a particularly challenging problem and was hoping for some guidance. Here is my problem. I have a point cloud containing millions of points. For each point in the set, I need to ...
2
votes
3answers
84 views

Beale's function and newton iteration

I am trying to find the minimum of the so called Beale’s function given by $f(x_1,x_2) = (1.5-x_1+x_1x_2)^2 + (2.25-x_1+x_1x_2^2)^2 + (2.625-x_1+x_1x_2^3)^2$ Using Newton iteration $x^{(k+1)} = ...
2
votes
1answer
65 views

Saving symbolic function to increase efficiency in Matlab

I have a lengthy expression which is calculated using symbolic differentiation of a rather complicated function. I now intend to call this resulting (symbolic function) in a for loop many times, and ...
0
votes
0answers
9 views

Experiment report with hypothesis for simulated model [on hold]

I'm setting up an experiment for a simulation. I'm not sure how to formulate the hypothesis. The model used in the simulation is the first iteration, so I'm just using 2 attributes, 1 independent (A) ...
1
vote
1answer
25 views

Maple stored variable to be read into Matlab

I have a a function $f(k)$ (calculated in Maple) which is huge and stored in a variable called 'sum' on my drive (with the help of 'save' command in Maple). Since the function is huge, Maple is unable ...
0
votes
0answers
30 views

How to connect two fitted B-spline curve?

I use B-spline curve fitting to obtain one smooth curve. If I obtain two smooth B-spline , how can I connect then smoothly. For example, I have 59 points((x0,y0,z0),...,(x58, y58, z58)) and I have two ...
1
vote
1answer
41 views

numerical integration of exponential which contains complex function

Hello everyone i'd like to get the result of Fresnel-Kirchhoff integral in paraxial approximation to the cylindrical diffracted wave and here is a part of my code and if it is solved gonna be carried ...
5
votes
1answer
73 views

Are there any algorithms “incrementally remove part of data (esp., old data)” from the existing SVD model of a data?

Sometimes it is meaningful to remove the influence of some old data from a SVD-based model, so as to reflect the most updated trends and provide more accurate results. I've seen there're incremental ...
2
votes
1answer
69 views

Poisson solver diverged

My 2D-Poisson solver is build for simulation of semiconductor. The algorithm is Gauss-Seidel iterative method. If I use simple PN junction for simulation testing, it diverged while I applied high ...
0
votes
0answers
31 views

library of efficient data types and algorithms [closed]

I come across LEDA(library of efficient data types and algorithms) for doing graph theory algorithms: http://www3.cs.stonybrook.edu/~algorith/implement/LEDA/implement.shtml I want to ask besides ...
0
votes
1answer
32 views

How to plot function with evenly spaced xvalues in Matlab

'Im trying to plot this function func=exp(x-sqrt(2))-cos(x-sqrt(2))-(x-sqrt(2)) in Matlab using 101 evenly spaced x values. If I just say fplot(fun,[-1 3], 'o') the graph is the correct shape but the ...
-3
votes
1answer
51 views

Mixed-Integer Linear Programing : get the maximum constant associated to a non null variable [closed]

Does anyone know a way get the maximum constant associated to a non null variable using Mixed-Integer Linear Programing ? I would like to get the variable $a$ in this description : $$ i = 1,\ldots,m ...
1
vote
1answer
39 views

Comparison of the time efficiency of an optimization problem formulated as a Network Flow model and Mixed Integer Programming

In combinatorial optimization, there are many problems that can be formulated as either Network Flow model or Mixed Integer Programming (MIP), e.g. supply chains, transportation, and graph-base ...
-4
votes
0answers
55 views

Can this specific Linear Program constraint be expressed? [closed]

Thanks for your time. I have a linear program and no idea how I could express a form of constraint and even if it's possible. Maybe someone here know a solution. A company assembly and sells a ...
1
vote
1answer
52 views

Mixed-integer quadratic programming, state of art [closed]

I used Gurobi with a MIQP with 26 binary variables and 26*4 interaction term without any other constraint. The speed is very slow already.... I want to ask what is the state of art of MIQP solvers. ...
0
votes
0answers
18 views

Results from TLE & SGP4 propagation - don't seem right & need help with interpretation [on hold]

I acquired a TLE of the ISS from internet and used the C++ SGP4 propagator to compute future position and velocity vectors of the Station. I am a little unsure about some aspects of results though and ...
2
votes
0answers
36 views

Mixed DG for Poisson with mixed BC's

I am trying to find a good reference on a proper weak formulation for mixed DG (Raviart Thomas and DG) formulation for a Poisson equation with mixed boundary conditions. Can anyone suggest a good ...
0
votes
1answer
43 views

2nd Order finite difference for 1D wave equation matlab issue

I'm trying verify that a 2nd order finite difference in space and time approximation of the 1D wave equation is really 2nd order. My Matlab implementation tells me otherwise - I'm not sure of what ...
1
vote
1answer
28 views

Transparent boundary conditions for finite element simulation of TDSE

I have implemented a version of Visscher's method for numerically solving the TDSE (A fast explicit algorithm for the time-dependent Schrödinger equation) (also described in Are there simple ways to ...
0
votes
0answers
21 views

Convected 2nd order tensor in component form [migrated]

I have a convected second order tensor that I'd like to write in component form. $\frac{D\mathbf{a}}{D t} = \frac{\partial \mathbf{a}}{\partial t} + \mathbf{v}\cdot\nabla\mathbf{a}$, where ...
2
votes
1answer
63 views

Solving a pair of high-degree polynomials in two variables with Maple

I have two algebraic equations I am trying to solve in Maple. They are: $14\,{a}^{26}{b}^{2}-91\,{a}^{24}{b}^{4}-364\,{a}^{22}{b}^{6}-1001\,{a} ...
2
votes
1answer
34 views

Is Langevin thermostat/equation correct when trying to model time-dependent behaviour of a molecule?

I've been taught that when simulating a biomolecule in thermal equilibrium, it's best to use the Langevin thermostat - an algorithm which produces a trajectory, which is a realization of a stochastic ...
1
vote
2answers
103 views

How to represent weighted nuclear norm of matrix variable X and minimize it by CVX function, or solve it by other possible packages

I want to minimize $f(x) = \mathrm{Tr}(\sqrt{\mathbf{X}^{T}\mathbf{X}}\mathbf{A})$, where $\mathbf{X}$ is an matrix variable of dimension $d \times d$, and $\mathbf{A}$ is a known matrix. I tried the ...
3
votes
2answers
62 views

How does constraint resolution affect the stability/accuracy of numerical integration?

I understand some basic analysis techniques (local truncation error, global error, zero-stable, absolute stable, etc.) of numerical integration. But I find it hard to apply these techniques in ...
2
votes
0answers
52 views

Euler Equation Eigensystem with Gravity in the Energy Flux

I am modifying a conservative form of the Euler equations with gravity in the energy flux (see previous question: Energy Conservation in Conservation Laws with Source Terms) for use in a Riemann ...
5
votes
1answer
131 views

Numerical evaluation of an elliptic integral in python

Goal: I need to evaluate numerically an integral of the following form: $$ \int_0^\infty \frac{dx}{(a^2+x)\sqrt{(a^2+x)(b^2+x)(c^2+x)}} $$ where $a,b,c \in \mathbb{R}$ are in the interval ...
2
votes
0answers
46 views

Maximize sum of Rayleigh quotients

I want to maximize the sum of Rayleigh quotients: $$\max_x\sum_{i=1}^n\frac{x^\top A_i x}{x^\top B_i x}$$ where $A_i$ and $B_i$ is positive definite. I've found a similar question here: minimization ...
0
votes
0answers
19 views

LBM for thermal anlysis

Can Lattice-Boltzmann methods be used for thermal analysis of radiation or conduction? (Hints for papers and libraries are highly appreciated.)
3
votes
1answer
68 views

Fast methods to solve an elliptic PDE if high accuracy is needed only in part of the domain

Does someone know a method to get cheap approximation of harmonic problems (and possibly local approximations)? Let me explain: I need to compute the solution of an harmonic problem \begin{equation} ...
0
votes
0answers
32 views

State of the art in pseudo-boolean optimization [closed]

Pseudo-boolean optimization is known to be NP-hard. What is the current state of the art (how many variables, interaction parameters) in solvers for pseudo-boolean optimization problems? What is the ...
0
votes
0answers
13 views

Max weighted subset (max sum diversification)

Given a set of elements $V$, with known cost $\pi_S$ for each subset $S \subset V$ and a monotone increasing function on the subsets $f(S)$ . I'm wondering if there is a pseudo-polynomial algorithm ...
0
votes
1answer
84 views

Domain Decomposition with PETSc

Does anyone have any experience on Domain Decomposition using PETSc library? I have used PETSc for creating my vectors and matrix within my C++ code. I also used KSP to solve the linear system. I ...
0
votes
1answer
31 views

Implicitly defined univariate function

So my fellow numerical computational peeps it may be that I am suffering from sleep deprivation but I'm struggling to numerically compute a function $u \rightarrow h(u)$ defined implicitly as follows: ...

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