From exact running times to complexity classes
Lax434175.ResultTransfer · concepts/Lax434175/ResultTransfer.lean · lax-434175
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Theorem
An algorithm stated with its exact running time — one program deciding the decision version within instructions on the word of every instance () — gives the coarser results by bounding alone, without looking at the program again. Let be the bit size of the word of an instance with a threshold, and its largest number.
Theorem.
- If , the problem is in P.
- If , it is solvable in pseudo-polynomial time.
- If for a function of the parameter , it is in P for every fixed value of .
- If for a computable and the parameter is computable in polynomial time on the words, it is fixed-parameter tractable in .
Theorem. A program deciding within exactly instructions decides within ().
Theorem. A program deciding within decides within with wide words (): the wide words are among the short ones.
Concept map
Evidence
This concept declares 6 statements. Each proof establishes one of them relative to its assumptions.
1 decidesWithin_of_exact proven
2 decidesWithinWide_of_decidesWithin proven
3 inP_of_decidesWithin proven
4 inPFixed_of_decidesWithin proven
5 isFPT_of_decidesWithin proven
6 pseudoPoly_of_decidesWithin proven
Lean source view on GitHub
| 1 | import Lax434175.Results |
| 2 | |
| 3 | /-! |
| 4 | --- |
| 5 | title: From exact running times to complexity classes |
| 6 | type: theorem |
| 7 | --- |
| 8 | An algorithm stated with its exact running time — one program deciding the |
| 9 | decision version within instructions on the word of every instance |
| 10 | (`Results.DecidesWithin`) — gives the coarser results by bounding alone, |
| 11 | without looking at the program again. Let be the bit size of the word of |
| 12 | an instance with a threshold, and its largest number. |
| 13 | |
| 14 | **Theorem.** |
| 15 | |
| 16 | 1. If , the problem is in P. |
| 17 | 2. If , it is solvable in pseudo-polynomial time. |
| 18 | 3. If for a function of the parameter , |
| 19 | it is in P for every fixed value of . |
| 20 | 4. If for a computable and the parameter is |
| 21 | computable in polynomial time on the words, it is fixed-parameter tractable |
| 22 | in . |
| 23 | |
| 24 | **Theorem.** A program deciding within exactly instructions decides within |
| 25 | (`Results.DecidesExact`). |
| 26 | |
| 27 | **Theorem.** A program deciding within decides within with wide words |
| 28 | (`Results.DecidesWithinWide`): the wide words are among the short ones. |
| 29 | -/ |
| 30 | |
| 31 | namespace Lax434175.ResultTransfer |
| 32 | open Lax434175.Problems Lax434175.Results Lax759944.BinaryWordEncoding |
| 33 | open Lax496464.WH_A2_FptReductions |
| 34 | |
| 35 | variable {P : Problem} (R : PReading P) |
| 36 | |
| 37 | axiom decidesWithin_of_exact {T : P.Inst → ℕ} (h : DecidesExact R fun x _ => T x) : DecidesWithin R T |
| 38 | |
| 39 | axiom decidesWithinWide_of_decidesWithin {T : P.Inst → ℕ} (h : DecidesWithin R T) : |
| 40 | DecidesWithinWide R T |
| 41 | |
| 42 | axiom inP_of_decidesWithin {T : P.Inst → ℕ} (h : DecidesWithin R T) |
| 43 | (hT : ∃ c d : ℕ, ∀ u x D, EncodesDecision R u x D → T x ≤ c * (bitSize u + 1) ^ d) : |
| 44 | InP R |
| 45 | |
| 46 | axiom pseudoPoly_of_decidesWithin {T : P.Inst → ℕ} (h : DecidesWithin R T) |
| 47 | (hT : ∃ c e d : ℕ, ∀ u x D, EncodesDecision R u x D → |
| 48 | T x ≤ c * (maxEntry u + 1) ^ e * (bitSize u + 1) ^ d) : |
| 49 | PseudoPoly R |
| 50 | |
| 51 | axiom inPFixed_of_decidesWithin {T : P.Inst → ℕ} (κ : TParameter P) (h : DecidesWithin R T) |
| 52 | (hT : ∃ (c : ℕ) (g : ℕ → ℕ), ∀ u x D, EncodesDecision R u x D → |
| 53 | T x ≤ c * (bitSize u + 1) ^ g (κ x D)) : |
| 54 | InPFixed R κ |
| 55 | |
| 56 | axiom isFPT_of_decidesWithin {T : P.Inst → ℕ} (κ : TParameter P) (h : DecidesWithin R T) |
| 57 | (hκ : IsParameterized (parameterized R κ)) |
| 58 | (hT : ∃ (f : ℕ → ℕ) (d : ℕ), Computable f ∧ ∀ u x D, EncodesDecision R u x D → |
| 59 | T x ≤ f (κ x D) * (bitSize u + 1) ^ d) : |
| 60 | IsFPT R κ |
| 61 | |
| 62 | end Lax434175.ResultTransfer |
| 63 |
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