experiment(cma): ablation finds WHY Qwen fails at Form-A — two distinct walls (refs #68)
Try-and-error ablation, minimal few-shot context, single shot per level, a ladder L0 (fn returns 42) to L7 (full SMA). Two ladders: base few-shot that only destructures, then one that also constructs (term-ctor). Finding: Qwen is NOT generally incapable. With minimal correct context it writes 6/8 tasks green, including ADTs, match, recursive fns, and Series use. The failures are two specific walls: - Wall 1 (cheap): unfamiliar constructs. It built lists with (app Cons ...) — calling the ctor like a function — because it had only seen match, never term-ctor. Adding ONE term-ctor example flipped L3 and L5 to green and removed the Cons error. The model generalises a construct from one example. - Wall 2 (hard): paren/nesting discipline at depth. The two that stay red (L4, L7) fail purely on bracketing, not knowledge. In L4 the recursive function is flawless; main closes a 4x-nested term-ctor value one paren early so the let body slides inside it — total paren count is BALANCED (43/43), the parens are just misplaced. Green/red tracks nesting depth, not feature. Examples do not fix it. This is the same weakness the full-SMA probes hit (run 2 had correct logic, died on brackets; run 3's long context tipped it into a seq-repetition loop). Takeaway: the bottleneck is the fully-parenthesised surface at depth, not the semantics. Natural next test: the .ail.json authoring form, which removes human paren-counting. Driver qwen_ablation.py; ladders in qwen-ablation-min.md and qwen-ablation-ctor.md; synthesis in qwen-ablation.md.
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# Qwen3-Coder-Next ablation — where does Form-A authoring break?
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**Model:** Qwen/Qwen3-Coder-Next; single-shot per level; minimal few-shot context.
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Each level is independent (fresh context, one call, no retry).
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---
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## L0_const — ✅ green
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ctx=BASE tokens: prompt=375 completion=37
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```
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(module m
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(fn answer
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(type (fn-type (params) (ret (own (con Int)))))
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(params)
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(body 42)))
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```
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## L1_arith — ✅ green
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ctx=BASE tokens: prompt=377 completion=50
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```
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(module m
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(fn triple
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(type (fn-type (params (own (con Int))) (ret (own (con Int)))))
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(params x)
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(body (app + x (app + x x)))))
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```
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## L2_print — ✅ green
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ctx=BASE tokens: prompt=372 completion=54
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```
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(module m
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body (seq (app print 7) (do io/print_str "\n")))))
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```
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## L3_adt — ✅ green
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ctx=BASE tokens: prompt=391 completion=140
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```
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(module m
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(data Light (ctor Red) (ctor Green))
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(fn code
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(type (fn-type (params (own (con Light))) (ret (own (con Int)))))
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(params x)
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(body
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(match x
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(case (pat-ctor Red) 0)
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(case (pat-ctor Green) 1))))
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body
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(seq (app print (app code (term-ctor Light Red))) (do io/print_str "\n")))))
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```
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## L4_rec — ❌ check
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ctx=BASE tokens: prompt=403 completion=194
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```
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(module m
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(data IntList (ctor Nil) (ctor Cons (con Int) (con IntList)))
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(fn length
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(type (fn-type (params (own (con IntList))) (ret (own (con Int)))))
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(params xs)
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(body
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(match xs
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(case (pat-ctor Nil) 0)
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(case (pat-ctor Cons _ t) (app + 1 (app length t))))))
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body
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(let xs (term-ctor IntList Cons 1 (term-ctor IntList Cons 2 (term-ctor IntList Cons 3 (term-ctor IntList Nil)))
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(seq (app print (app length xs)) (do io/print_str "\n"))))))
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```
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**`ail check`:**
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```
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error: [surface-parse-error] parse error: expected term, got `)` at byte 579
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```
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## L5_series_len — ✅ green
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ctx=SERIES tokens: prompt=613 completion=122
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```
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(module m
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body
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(let s (new Series (con Float) 3)
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(let s1 (app Series.push s 1.0)
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(let s2 (app Series.push s1 2.0)
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(let s3 (app Series.push s2 3.0)
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(seq (app print (app Series.len s3)) (do io/print_str "\n")))))))))
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```
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## L6_series_at — ✅ green
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ctx=SERIES tokens: prompt=621 completion=124
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```
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(module m
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body
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(let s (new Series (con Float) 3)
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(let s1 (app Series.push s 1.0)
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(let s2 (app Series.push s1 2.0)
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(let s3 (app Series.push s2 3.0)
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(seq (app print (app Series.at s3 0)) (do io/print_str "\n")))))))))
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```
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## L7_sma — ❌ check
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ctx=SERIES tokens: prompt=703 completion=285
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```
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(module m
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body
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(let s (new Series (con Float) 3)
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(let s1 (app Series.push s 1.0)
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(let s2 (app Series.push s1 5.0)
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(let s3 (app Series.push s2 3.0)
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(let s4 (app Series.push s3 8.0)
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(let s5 (app Series.push s4 6.0)
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(let s6 (app Series.push s5 2.0)
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(seq
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(seq
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(seq
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(seq
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(seq
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(app print (app / (app Series.total_count s3) 3.0))
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(do io/print_str "\n"))
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(app print (app / (app Series.total_count s4) 3.0)))
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(do io/print_str "\n"))
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(app print (app / (app Series.total_count s5) 3.0)))
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(do io/print_str "\n"))
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(app print (app / (app Series.total_count s6) 3.0)))
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(do io/print_str "\n"))))))))
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```
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**`ail check`:**
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```
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error: [surface-parse-error] parse error: expected `)` (end of let-term), got `(` at byte 980
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```
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---
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## Ladder
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- L0_const: ✅ green
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- L1_arith: ✅ green
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- L2_print: ✅ green
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- L3_adt: ✅ green
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- L4_rec: ❌ check
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- L5_series_len: ✅ green
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- L6_series_at: ✅ green
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- L7_sma: ❌ check
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File diff suppressed because one or more lines are too long
@@ -0,0 +1,75 @@
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# Why does Qwen3-Coder-Next fail at AILang Form-A? — ablation finding
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**Date:** 2026-06-02 **Model:** Qwen/Qwen3-Coder-Next (IONOS, temp 0.2)
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**Method:** try-and-error from a minimum upward. A ladder L0 (trivial) → L7
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(full SMA), each level run independently with minimal few-shot context, single
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shot. Two ladders: ladder 1 with a base few-shot that only *destructures*
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(`match`); ladder 2 after adding one example that *constructs* (`term-ctor`).
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Raw logs: `qwen-ablation-min.md` (ladder 1), `qwen-ablation-ctor.md` (ladder 2).
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Driver: `qwen_ablation.py`.
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## The two ladders
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| Level | task | ladder 1 (min) | ladder 2 (+term-ctor example) |
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|---|---|---|---|
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| L0 | fn returns 42 | ✅ | ✅ |
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| L1 | fn ×3 | ✅ | ✅ |
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| L2 | main prints 7 | ✅ | ✅ |
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| L3 | ADT + match | ❌ check | ✅ |
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| L4 | build list + recursive length | ❌ `Cons` unbound | ❌ paren misplace |
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| L5 | Series, print len | ❌ missing newline | ✅ |
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| L6 | Series.at | ✅ | ✅ |
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| L7 | full SMA | ❌ check | ❌ paren imbalance |
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One example of the missing construct moved Qwen from 4/8 to **6/8**.
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## The answer: it is NOT general incapacity — there are two distinct walls
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**Qwen is not "stupid" at Form-A.** With minimal, *correct* few-shot context
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it writes 6 of 8 tasks green — including ADTs, `match`, recursive functions,
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and Series library use (`new Series`, `push`, `at`, `len`). The two failures
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are specific and different in kind:
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### Wall 1 — unfamiliar constructs (SOLVABLE by one example)
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Qwen does not know constructs it hasn't seen, and guesses plausibly wrong:
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- L4 ladder 1: it built a list with `(app Cons 1 (app Cons 2 …))` and bare
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`Nil` — calling the constructor like a function → `unbound-var: Cons`. It
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had only seen `match`/`pat-ctor` (destructuring), never `term-ctor`
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(construction).
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- Adding ONE few-shot that uses `term-ctor` flipped L3 and L5 to green, and
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removed the `Cons`-as-function error in L4. The model generalises from a
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single example of a construct.
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This is the cheap wall: feed the construct once and it clears.
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### Wall 2 — paren/nesting discipline at depth (NOT solved by examples)
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The two that stayed red (L4, L7) both fail on **S-expression bracketing**,
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not on any missing knowledge:
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- L4 ladder 2: the `length` function is flawless. `main` builds
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`(let xs (term-ctor … (term-ctor … (term-ctor … (term-ctor IntList Nil)))`
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— closing the nested `term-ctor` value one paren too early, so the `let`
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body slides inside the value. **Total paren count is balanced (43 open / 43
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close)** — the parens are merely *misplaced*. The model is not under-closing
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globally; it loses track of the nesting structure at depth.
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- L7 (SMA): 49 open / 47 close — under-closed.
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The grin/red split tracks **nesting depth**, not feature: every green task is
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shallow (one or two levels), every red one is deeply nested (4× nested
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`term-ctor` in a `let`; the SMA's stream-loop composition). This is a
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mechanical limit on tracking deep paren nesting, and examples do not fix it —
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consistent with the earlier full-SMA probes (run 2: correct ownership
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threading, died on brackets; run 3: ~80k-token context tipped the same
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weakness into a non-terminating `(seq (seq …))` repetition loop).
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## Takeaway
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The bottleneck for this model on Form-A is the **fully-parenthesised surface
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itself** at depth, not the language's semantics or its vocabulary. Two
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levers follow, both deliberate next steps, not run here:
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1. Few-shot every non-obvious construct (cheap, clears Wall 1).
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2. For Wall 2, the surface is the problem — the natural test is the
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**`.ail.json` authoring form**, which removes human-style paren-counting
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(structure is carried by JSON nesting the model is far more trained on).
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The cma harness already renders both cohorts; this is the obvious A/B.
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@@ -0,0 +1,141 @@
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#!/usr/bin/env python3
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"""Ablation probe: WHY does Qwen3-Coder-Next fail at AILang Form-A?
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Try-and-error from a minimum upward. A ladder of tasks of increasing
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complexity (L0 trivial → L7 full SMA), each run INDEPENDENTLY: fresh,
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minimal few-shot context, single shot (no retry, no dialog accumulation —
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prior probes showed retries don't converge and long context degenerates).
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The first level that breaks localises the wall.
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Reads $IONOS_API_TOKEN (never printed). Live IONOS — run with consent.
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"""
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from __future__ import annotations
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import json, os, re, subprocess, urllib.request
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from pathlib import Path
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ENDPOINT = "https://openai.inference.de-txl.ionos.com/v1/chat/completions"
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MODEL = "Qwen/Qwen3-Coder-Next"
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REPO = Path(__file__).resolve().parents[2]
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AIL = os.environ.get("AIL_BIN", str(REPO / "target/debug/ail"))
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DOC = REPO / "experiments/2026-05-12-cross-model-authoring/qwen-ablation-ctor.md"
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DEMO_A = """(module demo_a
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(fn double
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(type (fn-type (params (own (con Int))) (ret (own (con Int)))))
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(params x)
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(body (app + x x)))
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body (seq (app print (app double 21)) (do io/print_str "\\n")))))"""
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DEMO_B = """(module demo_b
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(data IntList (ctor Nil) (ctor Cons (con Int) (con IntList)))
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(fn sum
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(type (fn-type (params (own (con IntList))) (ret (own (con Int)))))
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(params xs)
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(body
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(match xs
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(case (pat-ctor Nil) 0)
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(case (pat-ctor Cons h t) (app + h (app sum t))))))
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body
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(let xs (term-ctor IntList Cons 1 (term-ctor IntList Cons 2 (term-ctor IntList Nil)))
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(seq (app print (app sum xs)) (do io/print_str "\\n"))))))"""
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DEMO_S = """(module demo_s
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(fn main
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(type (fn-type (params) (ret (own (con Unit))) (effects IO)))
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(params)
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(body
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(let s (new Series (con Float) 3)
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(let s2 (app Series.push s 1.0)
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(let s3 (app Series.push s2 2.0)
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(seq (app print (app Series.len s3)) (do io/print_str "\\n"))))))))"""
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INTRO = ("AILang is a fully-parenthesised S-expression language (\"Form-A\"). "
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"Study these complete, valid example modules, then write the requested "
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"module. Return ONLY the AILang source for the module — no prose, no "
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"markdown fences.\n\n")
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BASE = INTRO + "Example 1:\n" + DEMO_A + "\n\nExample 2:\n" + DEMO_B + "\n"
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SERIES = (BASE + "\nExample 3 (uses the Series ring-buffer library — "
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"`(new Series (con Float) N)` allocates one of capacity N; "
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"`Series.push : (own (Series a)) (own a) -> (own (Series a))` appends "
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"and returns the new series; `Series.at : (borrow (Series a)) (own Int) "
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"-> (own a)` reads index i back from newest (0 = newest); "
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"`Series.len`/`Series.total_count : (borrow (Series a)) -> (own Int)`):\n"
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+ DEMO_S + "\n")
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SMA_OUT = "3.0\n5.33333\n5.66667\n5.33333\n"
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SMA_TASK = ("Write a module `m` computing a simple moving average, window 3, over "
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"the float stream 1.0, 5.0, 3.0, 8.0, 6.0, 2.0 using the Series library: "
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"create a Float Series lookback 3, push each value in turn, and after each "
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"push once at least 3 values have been pushed, print the average of the "
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"most recent 3 (their sum / 3.0) on its own line. Expected:\n" + SMA_OUT)
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# (id, context, task, expected_stdout_or_None[=check-only])
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STAGES = [
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("L0_const", BASE, "Write a module `m` with a function `answer` taking no parameters that returns the Int 42.", None),
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("L1_arith", BASE, "Write a module `m` with a function `triple` taking one Int parameter, returning it multiplied by 3.", None),
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("L2_print", BASE, "Write a module `m` whose `main` prints the Int 7 on its own line.", "7\n"),
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("L3_adt", BASE, "Write a module `m` with an ADT `Light` (ctors Red, Green) and a function `code` returning Int 0 for Red and 1 for Green via match.", None),
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("L4_rec", BASE, "Write a module `m` with an IntList ADT (Nil/Cons), a function `length` counting elements by recursion, and a `main` that prints the length of the list [1,2,3] on its own line.", "3\n"),
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("L5_series_len", SERIES, "Write a module `m` using the Series library: create a Float Series lookback 3, push 1.0 then 2.0 then 3.0, then print its Series.len on its own line.", "3\n"),
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("L6_series_at", SERIES, "Write a module `m` using the Series library: create a Float Series lookback 3, push 1.0 then 2.0 then 3.0, then print (Series.at on index 0, the newest) on its own line.", "3.0\n"),
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("L7_sma", SERIES, SMA_TASK, SMA_OUT),
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]
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def call(system, task):
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body = json.dumps({"model": MODEL, "temperature": 0.2, "max_tokens": 1500,
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"messages": [{"role":"system","content":system},{"role":"user","content":task}]}).encode()
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req = urllib.request.Request(ENDPOINT, data=body, headers={
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"Authorization": f"Bearer {os.environ['IONOS_API_TOKEN']}", "Content-Type":"application/json"})
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with urllib.request.urlopen(req, timeout=120) as r:
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d = json.loads(r.read())
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return d["choices"][0]["message"]["content"], d.get("usage", {})
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def extract(resp):
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m = re.search(r"```(?:[a-zA-Z]*)?\n(.*?)```", resp, re.S)
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code = m.group(1) if m else resp
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i = code.find("(module")
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return code[i:].strip() if i >= 0 else code.strip()
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def evaluate(code, expected):
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m = re.search(r"\(module\s+([A-Za-z_][A-Za-z0-9_]*)", code)
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name = m.group(1) if m else "m"
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f = Path(f"/tmp/abl/{name}.ail"); f.parent.mkdir(exist_ok=True); f.write_text(code+"\n")
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chk = subprocess.run([AIL,"check",str(f)], capture_output=True, text=True)
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if chk.returncode != 0: return "check", (chk.stderr or chk.stdout).strip()
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if expected is None: return "green", "(check-only)"
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run = subprocess.run([AIL,"run",str(f)], capture_output=True, text=True)
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if run.returncode != 0: return "run", (run.stderr or run.stdout).strip()
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if run.stdout != expected: return "output", f"got {run.stdout!r}, expected {expected!r}"
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return "green", run.stdout
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def main():
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log = ["# Qwen3-Coder-Next ablation — where does Form-A authoring break?\n",
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f"**Model:** {MODEL}; single-shot per level; minimal few-shot context.\n",
|
||||
"Each level is independent (fresh context, one call, no retry).\n", "---\n"]
|
||||
summary = []
|
||||
for sid, ctx, task, exp in STAGES:
|
||||
resp, usage = call(ctx, task)
|
||||
code = extract(resp)
|
||||
stage, fb = evaluate(code, exp)
|
||||
ok = stage == "green"
|
||||
mark = "✅ green" if ok else f"❌ {stage}"
|
||||
summary.append((sid, mark))
|
||||
print(f"{sid}: {mark}")
|
||||
log += [f"## {sid} — {mark}",
|
||||
f"\nctx={'BASE' if ctx is BASE else 'SERIES'} tokens: "
|
||||
f"prompt={usage.get('prompt_tokens','?')} completion={usage.get('completion_tokens','?')}\n",
|
||||
"```\n"+code+"\n```\n",
|
||||
("" if ok else f"**`ail {stage}`:**\n```\n{fb[:800]}\n```\n")]
|
||||
log += ["\n---\n## Ladder\n"] + [f"- {s}: {m}" for s,m in summary]
|
||||
DOC.write_text("\n".join(log))
|
||||
print("doc →", DOC)
|
||||
|
||||
if __name__ == "__main__":
|
||||
main()
|
||||
Reference in New Issue
Block a user