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cost.sx: injected cost-fn keeps media costs opaque. critical-path = longest weighted path (= unlimited-worker makespan); makespan sums each batch's slowest node (full plan == critical path, serial == total-work); speedup = work/makespan. cost 13/13, total 115/115. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
67 lines
1.9 KiB
Plaintext
67 lines
1.9 KiB
Plaintext
; lib/artdag/cost.sx — cost model for the scheduler: per-node weights, critical
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; path (min makespan with unlimited parallelism), plan makespan under batching/cap,
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; total serial work, and the resulting speedup. Costs come from an injected
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; cost-fn (op params) -> number so media-op costs stay opaque. Depends on dag.sx.
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(define artdag/const-cost (fn (op params) 1))
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(define
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artdag/op-cost
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(fn
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(table)
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(fn (op params) (if (has-key? table op) (get table op) 1))))
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(define
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artdag/-node-cost
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(fn
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(dag cost-fn id)
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(let
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((n (artdag/dag-get dag id)))
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(cost-fn (artdag/node-op n) (artdag/node-params n)))))
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(define
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artdag/-max
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(fn (xs) (reduce (fn (mx x) (if (> x mx) x mx)) 0 xs)))
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; longest weighted path through the dag = makespan with unlimited workers.
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(define
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artdag/critical-path
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(fn
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(dag cost-fn)
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(let
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((ft (reduce (fn (m id) (let ((maxdep (artdag/-max (map (fn (d) (get m d)) (artdag/node-inputs (artdag/dag-get dag id)))))) (assoc m id (+ (artdag/-node-cost dag cost-fn id) maxdep)))) {} (artdag/dag-order dag))))
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(artdag/-max (map (fn (id) (get ft id)) (keys ft))))))
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; estimated wall-clock for a plan: each batch runs in parallel (costs its
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; slowest node), batches run in sequence.
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(define
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artdag/makespan
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(fn
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(dag plan cost-fn)
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(reduce
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(fn
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(total batch)
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(+
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total
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(artdag/-max
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(map (fn (id) (artdag/-node-cost dag cost-fn id)) batch))))
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0
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plan)))
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; total serial work = sum of all node costs.
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(define
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artdag/total-work
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(fn
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(dag cost-fn)
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(reduce
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(fn (s id) (+ s (artdag/-node-cost dag cost-fn id)))
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0
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(keys (artdag/dag-nodes dag)))))
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; speedup of a plan vs running everything serially.
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(define
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artdag/speedup
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(fn
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(dag plan cost-fn)
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(/ (artdag/total-work dag cost-fn) (artdag/makespan dag plan cost-fn))))
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