[docs] Add a Scheduling Halide Pipelines guide

[derek-gerstmann]

Adds a new documentation guide, Scheduling Halide Pipelines, covering how
Halide pipelines are scheduled and the strategies, directives, and techniques
for optimizing performance for a target.

What's here

• doc/SchedulingHalidePipelines.md — the guide's landing page: a four-part
  overview plus an annotated table of contents. Its 21 chapters live under
  doc/scheduling/. The four parts are:
  • Part I — The Model: the objects being scheduled, how a pipeline is
    realized, and bounds inference.
  • Part II — Scheduling for Performance: the shapes fast pipelines take on
    CPUs and GPUs, how to find what to fix, plus recipes and pitfalls.
  • Part III — Scheduling Directives: how to read a loop nest, then each
    directive and exactly what it does.
  • Part IV — Reference: a directive index, a pre-flight checklist, and a
    worked example.
• Indexed in doc/guides.md.
• Wired into the Sphinx docs build (doc/CMakeLists.txt): the landing page
  and every chapter are staged into the Sphinx source tree, and the chapters
  are pulled in via a hidden toctree on the landing page so they render into
  the website and appear in the navigation.

Testing

Built the documentation site locally with sphinx-build (exit 0, no warnings):
the landing page and all 21 chapters render, cross-links resolve, and the
chapters appear in the sidebar nav.

Docs-only change — no source, public-API, or Python-binding impact.

🤖 Generated with Claude Code

Co-authored-by: David Zhao Akeley 25728234+akeley98@users.noreply.github.com
Co-authored-by: Andrew Adams andrew.b.adams@gmail.com
Co-authored-by: Karima Ma 10568169+KarimaMa@users.noreply.github.com
Co-authored-by: Claude Opus 4.8 noreply@anthropic.com

[alexreinking]

This seems like almost the exact structure of a Claude/agent skill. Should we add a .claude/skills/scheduling/SKILL.md that tells Claude to read this guide when asked to schedule something?

[alexreinking]

Also, is the point of this to be AI-readable first or human-readable first? There is a lot of AI-ese in there.

[derek-gerstmann]

Yes, adding a Claude SKILL.md that says to read this guide would be a great addition.

The intent was to make it user readable, but I rewrote it and reformatted it from a distillation of LLM specific docs, so there are definitely still leftover snippets that could use some rewording, adjustments. But we felt it was complete enough to open a PR to get comments, edits, feedback, etc.

[alexreinking]

For other reviewers, the link to the rendered Markdown is here: https://github.com/halide/Halide/blob/dg/scheduling_guide/doc/SchedulingHalidePipelines.md

[derek-gerstmann]

Added Claude SKILL.md. It also recommended a references/directives-cheatsheet.md.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.88%. Comparing base (a95f4de) to head (5a2795a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9435      +/-   ##
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- Coverage   70.07%   69.88%   -0.20%     
==========================================
  Files         261      261              
  Lines       79462    79462              
  Branches    19365    19365              
==========================================
- Hits        55684    55531     -153     
- Misses      17908    17965      +57     
- Partials     5870     5966      +96     

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