The compression theorem from its three stages #
Blueprint thm:compression, its proof (paper recursive.tex, Section "Proof of Theorem
compression"; ledger nodes 1.5, 1.5.7, 1.5.8): Compress is introspection at ℓ = 7,
then answer reduction at (λ, μ, σ(λ)), then parallel repetition at (λ, τ, β), and its
guarantees are those of the three stages chained through the margins of
MIPRE.Foundations.Pipeline.Margin. GapCompression.ofPipeline is that composition: from an
Introspection 7, an AnswerReduction 5 and a Repetition 7 it builds a GapCompression.
Oracularization is not a stage of Compress (it is the first step of the proof of answer
reduction) and is not consumed here.
The parameters, all determined by the three structures:
σ(λ): the paper's⌈C λ^C⌉, any polynomial inλcomputable in polynomial time that dominates the sizeC(λ + 1)^Cof the introspective decider and the sizes₁(λ)of the introspective sampler — the second because answer reduction runs the input sampler through the universal machine, whose overhead grows with the program simulated, so its complexity clause asks|𝒮|, |𝒟| ≤ σ. It issigmaFun C_σ λ, theC_σ-fold iterate ofn ↦ 2^{2·size n}on2λ + 1, which is2^{C(size λ + 2)}at least and is computed by iteratinglamProg; there is no polynomial-time arithmetic in the toolkit to compute the paper's expression directly, and any dominating polynomial serves.μ: the margin claimexists_mu, at leastC + 1: at leastCso that the introspective verifier is within answer reduction's input budget, and positive, as answer reduction's completeness asks.β: an exponent withpoly((λn + 1)^μ + σ(λ) + λ + n)^(μ + 1) ≤ (λn + 1)^β, the parse length handed to repetition, dominating the ambient answer bound of the answer-reduced verifier.τ: the repetition exponentexists_tau, from the lower boundε₂ ≥ x^{-P}ofexists_eps2_lower, against the parse length2^{β(|λ| + |n|)} ≤ (λn + 1)^{6β}.C₀: the largest of the thresholds —2, the introspection margin's, the margin claim's, the lower bound's, answer reduction's ownC_ar, andτ.
The complexity accounting is PolyBounded arithmetic: every bound of the repeated verifier at
(λ, n) is a monotone polynomial expression in λ, n, σ(λ) and the sizes of the programs
along the chain, hence at most a polynomial in n + λ (bound). The value chain is the one
of rem:compression-chain: each soundness clause contrapositively, landing inside the margin
the previous stage left.
The size parameter σ #
n ↦ 2^{2·size n} as a polynomial-time function (lamProg).
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sigmaFun C: the C-fold iterate of n ↦ 2^{2·size n} on 2n + 1, a polynomial-time
function of n bounded below by 2^{C(size n + 2)} and above by a polynomial in n.
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The parameters #
A bound on the size of the introspective sampler's program.
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- MIPRE.Pipeline.s₁ I lam = Polynomial.eval (4 * lam.size + 1) I.samplerProg.timeBound
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The coefficient of the monomial bound on s₁.
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- MIPRE.Pipeline.cS I = (∑ i ∈ Finset.range (I.samplerProg.timeBound.natDegree + 1), I.samplerProg.timeBound.coeff i) * 4 ^ I.samplerProg.timeBound.natDegree
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The exponent of σ: large enough that C_σ (λ + 1)^{C_σ} dominates both the introspective
decider's size C(λ + 1)^C and the introspective sampler's size s₁.
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σ(λ) = sigmaFun C_σ λ.
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- MIPRE.Pipeline.sigma I lam = (MIPRE.Pipeline.sigmaFun (MIPRE.Pipeline.Csig I)).toFun lam
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μ ≥ 1, which answer reduction's completeness asks.
β, the parse-length exponent handed to repetition.
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- MIPRE.Pipeline.beta I A = ⋯.choose
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τ, the repetition exponent, against the parse length 2^{β(|λ| + |n|)} ≤ (λn + 1)^{6β}.
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- MIPRE.Pipeline.tau I A R = ⋯.choose
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(λn + 1)^τ ≤ k(n).
The threshold of the introspection margin, ⌈(4a)^{1/b}⌉.
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C₀, the threshold of the compression theorem.
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- MIPRE.Pipeline.C₀ I A R = max (max (max 2 (MIPRE.Pipeline.C₁ I)) (max (MIPRE.Pipeline.N₁ I A) (MIPRE.Pipeline.N₂ I A))) (max A.C (MIPRE.Pipeline.tau I A R))
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The data #
The answer-reduced verifier, at level 7 = max (5 + 2) 5.
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- MIPRE.Pipeline.arOutput I A V₁ lam = A.output V₁ lam (MIPRE.Pipeline.mu I A) (MIPRE.Pipeline.sigma I lam)
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The answer-reduced sampler, at level 7.
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- MIPRE.Pipeline.arSampler I A S lam = A.sampler S lam (MIPRE.Pipeline.mu I A) (MIPRE.Pipeline.sigma I lam)
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The compressed sampler 𝒮^compr_λ.
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- MIPRE.Pipeline.sampler I A R lam = R.sampler (MIPRE.Pipeline.arSampler I A (I.sampler lam) lam) lam (MIPRE.Pipeline.tau I A R)
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Its program, as a polynomial-time function of λ.
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Compress: the program of the compressed decider, as a polynomial-time function of the
input programs and λ.
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The output of Compress on any input, as a 7-level normal form verifier.
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- MIPRE.Pipeline.output I A R V lam = R.output (MIPRE.Pipeline.arOutput I A (I.output V lam) lam) lam (MIPRE.Pipeline.tau I A R) (MIPRE.Pipeline.beta I A)
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The accounting #
A bound on the size of the encoded parameters (λ, μ, σ(λ)).
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- MIPRE.Pipeline.pArg I A lam = 4 * lam.size + 1 + (MIPRE.Cost.esize (MIPRE.Pipeline.mu I A) + (4 * (MIPRE.Pipeline.sigma I lam).size + 1) + 1) + 1
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A bound on the size of the answer-reduced verifier, as a function of λ.
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The bound of the answer-reduced verifier at (λ, n).
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- MIPRE.Pipeline.arBound I A lam n = MIPRE.AnswerReduction.outBound A.bound lam (MIPRE.Pipeline.mu I A) (MIPRE.Pipeline.sigma I lam) n
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The answer-reduced verifier's input-size degree. The pipeline fixes μ, so this
degree is independent of λ, n, and the input verifier.
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The running-time bound of the compressed verifier at (λ, n).
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The answer bound of the compressed verifier at (λ, n).
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- MIPRE.Pipeline.ansB I A R lam n = Polynomial.eval (MIPRE.Repetition.ansArg lam (MIPRE.Pipeline.tau I A R) (MIPRE.Pipeline.beta I A) n) R.ansBound
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Both bounds, as one function of z = n + λ.
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- MIPRE.Pipeline.G I A R z = MIPRE.Pipeline.timeB I A R z z + MIPRE.Pipeline.ansB I A R z z
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The polynomial poly(n, λ) of the compression theorem.
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- MIPRE.Pipeline.bound I A R = ⋯.poly
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The introspective verifier is within answer reduction's input budget.
The answer-reduced verifier is within its bound.
The compressed verifier is within its bounds.
The answer bound of the answer-reduced verifier is below the parse length handed to
repetition, for λ ≥ 1 and n ≥ 1.
The value chain #
Completeness of Compress: the three completeness clauses chained.
Soundness of Compress in a value model, value form: the three stages' soundness
clauses in the model, contrapositively, through the margins. The margins and the parameters are
the same in every model; only the clauses are the model's.
Soundness of Compress, value form: output_val_le in the tensor-product model, where
the stages' own soundness fields are the clauses.
The compression theorem from its stages (blueprint thm:compression, proof): an
Introspection 7, an AnswerReduction 5 and a Repetition 7 give a GapCompression.
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The composed compression is sound in every value model in which its three stages are
(item (c) of Phase 1 of planning/mipco-track.md). In the tensor-product model the stages'
own fields are the three clauses, and this is GapCompression.sound_tensor; in the
commuting-operator model it reduces the one hypothesis of the conditional MIP^co = coRE to the
three stages' clauses in ω_co.