Maintaining consistent vertex indexing

  • When using adjacency matrices, you must establish a consistent mapping between vertex names and integer indices. Decide early whether to use 0-based indexing (like Python/C) or 1-based indexing (like MATLAB/R), and stick with it throughout your implementation.
  • Create an explicit vertex index map that translates from vertex labels to matrix positions. This dictionary or array should be created once at initialization and referenced whenever accessing the matrix, preventing off-by-one errors and misaligned data.
  • Inconsistent indexing leads to subtle bugs that are hard to detect: edges may appear to exist where they don't, weights get assigned to wrong vertex pairs, and algorithms produce incorrect results. These bugs often pass tests with small graphs but fail on larger datasets.
  • Best practice: define your vertex ordering explicitly at the start, document it clearly, and use named constants or a lookup function rather than hardcoding numeric indices. This makes code more maintainable and reduces the chance of index-related errors when modifying or extending your implementation.