claimroutineinferred_dep

Tuple-by-tuple algorithm computes Z_E

Claim·§3.3 Separating the sum by fixing measurements·inside lemSeparating sums by fixing measurements

Statement (paper)

The algorithm, which processes the measurement tuples y⃗∈Y\vec y\in\mathcal Y one at a time starting from Z=0AZ=0_{\mathcal A}, skips each tuple for which some Xg(yg)\mathcal X_g(y_g) is empty, and otherwise computes p=∏g=1rΣg(y⃗)p=\prod_{g=1}^r\Sigma_g(\vec y) by scanning u∈{0,1}Sgu\in\{0,1\}^{S_g} and adding Ag(u+∑h≠gxˉh)A_g\bigl(u+\sum_{h\ne g}\bar x_h\bigr) to ss whenever Cgu=ygC_gu=y_g and ui=1u_i=1 for i∈E∩Sgi\in E\cap S_g, and then updates Z←Z+pZ\leftarrow Z+p, terminates with Z=ZEZ=Z_E.

In plain English

The algorithm that loops over measurement tuples y⃗∈Y\vec y\in\mathcal Y, skips tuples where some Xg(yg)\mathcal X_g(y_g) is empty, computes p=∏gΣg(y⃗)p=\prod_g\Sigma_g(\vec y) by scanning each {0,1}Sg\{0,1\}^{S_g}, and accumulates Z←Z+pZ\leftarrow Z+p, ends with Z=ZEZ=Z_E.

Why it's here

This is the correctness step: by the factorization claim, ZEZ_E is the sum over tuples of the products ∏gΣg(y⃗)\prod_g\Sigma_g(\vec y), with empty tuples contributing zero. The algorithm computes exactly these terms, since each Σg(y⃗)\Sigma_g(\vec y) is the sum of AgA_g at the shifted argument over uu with Cgu=ygC_gu=y_g and ui=1u_i=1 on E∩SgE\cap S_g. Adding the products one at a time therefore yields ZEZ_E.
Classified routine:
A direct correctness check for the enumeration loop: it computes each per-part sum by brute force and adds up the products, matching the factorization in the preceding claim (claim-lem-measurement-separation-1) term by term.

Sources

PaperOpen
Section
§3.3 Separating the sum by fixing measurements
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main_full_version.tex:1850
Leannot aligned

Phase 2 aligns this node to a Lean declaration.

Friction

  • info
    inferred_dep
    outline: "Tuple-by-tuple evaluation algorithm" rests on claim-lem-measurement-separation-1