Add HTSim traffic generation, simulation automation, and plotting utilities

[FrancescoSaletti03]

Description of changes

This PR adds a collection of Python utilities developed to support HTSim experiments and workflow automation.

The new scripts provide:

• traffic matrix generation for collective communication workloads;
• automation of repeated simulation runs;
• HTSim log parsing and visualization;
• plotting utilities for performance analysis.

Supported workloads and collectives include:

• AllGather:

  • Ring
  • Bruck
  • Recursive Doubling
  • Binary Exchange

• AllReduce:

  • Ring
  • Butterfly

• AllToAll communication patterns

• Permutation / Incast / Outcast-Incast traffic patterns

Additional updates:

• Added visualization tools for flow execution and host-to-host utilization.
• Added README documentation with usage examples and repository organization.
• Standardized comments and documentation in English.

How to run

Generate a traffic matrix:

python gen_allgather_ring.py output.cm 64 64 1048576 1

Run simulations:

python run_simulation.py allgather ring

Generate plots:

python plot_fattree_flows.py simulation.log

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PR Impact Assessment

Interaction with CMS specification

None

Impact on default behavior

Add new feature not enabled by default

Impact on performance

No impact on simulator runtime behavior by default.

This PR mainly introduces:

• external utility scripts;
• traffic matrix generators;
• analysis and plotting tools.

Simulation behavior is unchanged unless the new scripts are explicitly used.

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Merging instructions

PR dependencies

None

Should the PR commit history be kept

No ("squash and merge")

This PR needs approval from

@DanieleDeSensi