Spanning-forest cluster linearization

The programmer has made significant improvements to the Linearize() function in Bitcoin Core, with their updated version available at their GitHub repository. This new implementation is designed to perform full, optimal linearizations from scratch on a selected collection of challenging clusters that have been encountered on the network. These clusters were deemed "hard" based on several metrics applied to the previous method, though it's acknowledged that these might not represent the worst-case scenarios for the newly adopted spanning-forest algorithm.

Benchmark comparisons between the master branch and the new implementation show substantial performance enhancements across various examples. The benchmarks are presented as microseconds taken by the master version versus the updated version for a series of transactions labeled from LinearizeOptimallyExample00 to LinearizeOptimallyExample19. For instance, the timing for transaction LinearizeOptimallyExample00 improved from 70.6 microseconds on the master to 21.1 microseconds with the new approach. Similar improvements are observed across all listed examples, highlighting the efficiency gains. Some transactions exhibit dramatic reductions in processing time, such as LinearizeOptimallyExample10, which went from 371,677.6 microseconds on the master to just 24.1 microseconds.

This data underscores the effectiveness of the new linearization process, indicating not only improvements in speed but potentially also in the robustness of handling transactions considered difficult by previous standards. The enhancements span a wide range of cases, reflecting the general applicability and improved performance of the updated method over the existing one.