difference between dissect in matlab and METIS_NodeND in Metis?

Hello everyone,

I find that dissect in matlab utilize the METIS library, and it can choose the number of separator, which is also the number of subdomain.

But it seems like that there is no choice of the number of separator in the interface METIS_NodeND in METIS.

So what is the difference between the dissect and METIS_NodeND?

Answer 1

[akshatsood]

Hi @Biyi Wang,

The "dissect" function in MATLAB and the "METIS_NodeND" function from the METIS library both deal with graph partitioning and ordering, but they serve slightly different purposes and have different capabilities.

METIS is a library designed for partitioning graphs, finite element meshes, and producing fill-reducing orderings for sparse matrices. It is widely used for tasks like domain decomposition in parallel computing.

The "METIS_NodeND" function focuses on computing a nested dissection ordering of a graph. This is a technique used to reduce fill-in during matrix factorization, which is crucial for solving sparse linear systems efficiently. It does not directly allow the user to specify the number of separators or subdomains. Instead, it focuses on producing an ordering that minimizes the fill-in by recursively partitioning the graph.

The "dissect" function in MATLAB is also used for graph partitioning and ordering, leveraging the METIS library to achieve this. One of the unique features of this function is that it allows users to specify the number of subdomains, which indirectly influences the number of separators. This can be useful in scenarios where specific partitioning constraints are required, such as in domain decomposition methods for parallel computing.

Key Differences

1. User Control: MATLAB’s "dissect" provides more user control over the number of separators/subdomains, which is not directly available in "METIS_NodeND".
2. Application Focus: While both functions aim to optimize graph partitioning and ordering, "dissect" is more suited for applications requiring specific partitioning configurations, whereas "METIS_NodeND" is optimized for fill-reducing orderings without explicit control over partitioning.

I hope this helps.

[Biyi Wang]

Hi~@akshatsood.

Thank you for your nice answer, it gave me a clearer understanding of the difference between the two interfaces.