22.12.25 (inclusive)

Monetary

MVP

ICT tasks

Media sphere

Smart Field Information Systems

Software/ IS,

Mobile app

Let's consider the basic version of the program P₀ and two branches of changes p₁ and p₂. The semantic requirement for the result M = Merge(p₁, p₂): 1) for all valid inputs x, the behavior of M(x) is consistent with p₁(x) and p₂(x) in terms of already implemented features; 2) no branch loses its fixes; 3) Merge is deterministic and completes in a finite time. To prove that such a problem has no solution in the general case, it suffices to note that we essentially need to solve the program equivalence problem: to verify that M(x) and P₁(x) behave identically for all inputs x in the domain where the branch p₁ does not affect the changes in p₂. The equivalence of arbitrary programs in Turing‑complete languages is a classic example of an unsolvable problem.

The task of "a universal semantic merge that always produces the correct result" is generally unsolvable. You can build: • practical heuristic merge engines for specific languages and templates; • formal verification systems for narrow domains; • merge+testing hybrids. But the formulation in which the algorithm is required to provide absolute guarantees for any code in the repository contradicts the fundamental limitations of computability theory.

Sergeev I.A.