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# Questions tagged [topology]

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### How to topologically classify points in 3d space generating a surface?

Say I have N points sampled on a surface in 3 dimensions (ie. points on the surface of a sphere, 1-torus etc.). Is there an algorithm that would be able to count the number of holes in the surface ...
1 vote
28 views

### ensure connectivity in geometric optimization

I am working on parts of my master-thesis and got to a problem which I would like to solve and develop some algorithm for. Basically I am dealing with 2d-geometry which I would like to represent using ...
162 views

### How to handle coplanarity in convex hull?

I implemented the $O(n^2)$ convex hull algorithm. That is: Find a triangle known to be in the hull (by finding the lowest point, a point connected to it in the 2D convex hull, and the point that ...
182 views

### Minimum Number of Unique Identifiers for a Grid of Cells

I have a grid of cells, X cells wide by Y cells high. Each cell has four corners, NW, NE, SW and SE. Each corner is shared with adjacent neighbors; i.e., a cell's SW corner is the NW corner of the ...
149 views

### Does this esoteric representation of integers have decidable equality?

Consider the following datatypes in Haskell: data Foo = Halt | Iter Foo newtype BigInt = BigInt {nthBit :: Foo -> Bool} Foo ...
1 vote
214 views

### How to turn a 3D polytope into a mesh?

Let us say you have a polyotpe define as the intersection of halfplanes. That is you are given N half-spaces. The polytope is the volume defined by all points which lie on the positive side of all N ...
43 views

### Convert NURBS surface into Cubic Bezier Surface

The following post discussed how to convert(approximate) NURBS curve into cubic Bézier curve: Convert NURBS curve into Cubic Bezier Curve I am trying to come up with an algorithm that converts(...
3k views

### How to do a reverse topological sort using depth first search?

I'm doing a replacement for the venerable make utility that will support, among other things, automatic cleaning. The utility figures out automatically what files ...
75 views

### Recovering graph given degrees and connectivity information

I have a graph and don't know how nodes in it are connected to each other. I know the number of nodes in the graph. I know the degree of each node in the graph. I know that given any node $A$ that ...
1 vote
80 views

### If a computer can demonstrate singleton sets are closed, is the space Hausdorff?

In Haskell, I made a class of admissible (that is, second-countable and $T_0$) spaces: ...
38 views

### How to get the minimal enclosed polyhedra in a Line framework (points connectivity lists)?

Greetings all and thank you. I'm a Ph.D. candidate working on a force structure's 3D tessellation project and get stuck. I've simplified the system into a set of lines linked together which formed a ...
1 vote
36 views

### How to compute all inequivalent (under Aut(P)) nonnegative integer weight assignments (with fixed sum) to the vertices of a finite poset P?

Let $P$ be a poset on $n$ points, $\text{Aut}(P)$ its automorphism group, and $a_1,a_2,\dots,a_k$ the lengths of the orbits under $\text{Aut}(P)$. Goal: An algorithm to generate a member from each ...
1 vote
580 views

### What's an example of a planar graph with two embeddings whose geometric duals are nonisomorphic?

How to prove that the dual of the dual of a connected planar graph $G$ is isomorphic to $G$? In the post linked above, the user "plop" gives a great response where they claim, in particular, ...
96 views

### Is it valid to make an admission of a topological space by a "partial quotient map"?

It is well-known that the Sierpiński space, $\{F,T\}$ endowed with topology $\{\emptyset, \{F\},\{F,T\}\}$, is admissible. I tried to implement it in Haskell. First I implement $\mathbb{N}$ (including ...
25 views

### Classification of the Summit supercomputer

Can we classify a supercomputer in more than one group? For example, Flynn's classification, classification according to topology, classification according to memory access. For the Summit ...
59 views

### What does point-free mean mathematically?

Point-free style is generally taken to mean a style of programming without explicit variables. I have some intuitions on point-free style but I want to know what the formal mathematical definition is. ...
103 views

### Closest point in embedded simplicial complex

Suppose I have a simplicial $k$-complex $\mathcal S$ whose vertices are embedded in Euclidean space $\mathbb R^n$, for roughly $k< n\leq 6$. Examples include triangle mesh surfaces ($k=2$) embedded ...
24 views

1 vote