How statement and proof provenance work
The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.
- Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
- AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
- AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.
These labels describe origin, not correctness: citations and verification chips remain separate evidence.
FALSE: machine invariance means equivalent models perform exactly the same number of steps
Statement
False claim: whenever one translates a computation between standard machine models with the same computability power, the translated computation takes exactly the same number of steps.
Facts & Assumptions
Given: The false claim above.
Whenever one translates a computation between standard machine models with the same computability power, the translated computation takes exactly the same number of steps.
Polynomial-time and polynomial-space computation are model-invariant only up to asymptotic overhead, by Polynomial-time and polynomial-space computation are invariant across standard machine models.
A one-tape machine is the case of the deterministic multitape model, whose transitions read, write, and move each tape head once per step (Multitape and nondeterministic Turing machine variants).
Refutation
Let be a one-tape scanning machine, regarded by [L2] as a multitape machine with one tape. Translate it to an equivalent one-tape machine by inserting, before every original transition, a two-step right-then-left excursion that changes no tape symbol and records the finitely many encountered symbols in the control state. The third step performs the original transition. Thus has exactly the same behavior as but uses three steps for every nonhalting step of .
On every input for which takes a positive number of steps, the translated computation takes three times as many, contradicting [A1]. This is consistent with [L1]: robustness preserves asymptotic complexity classes, not literal equality of running times.
Depends on
Used by
Nothing in the library uses this result yet.
Dependency tree · two levels
6 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- Eric Blais, Models of Computation, 7. Time Complexity (standard reference, not scraped)