t81-foundation

Determinism Surface Registry

1. Purpose

Define what is and is not guaranteed to be deterministic in the T81 system.

Clarify that determinism guarantees apply only to explicitly verified surfaces.

Threat modeling for these surfaces is documented in DETERMINISM_THREAT_MODEL.md.

Reference:

2. Definition of a Determinism Surface

A determinism surface is:

A subsystem boundary for which identical input and configuration must produce bit-identical output across supported architectures. “Supported architectures” are defined by the platforms listed in the root README under Compatibility for the current major version.

Clarify:

3. Verified Determinism Surfaces

Surface Scope Guarantee Verification Mechanism CI Enforced Status
TISC Opcode Semantics Instruction Behavior Bit-Exact tests/cpp/vm_determinism_property_test.cpp
tests/cpp/test_tritwise_backend_equivalence.cpp		 Yes (ci.yml) Verified
VM Interpreter Execution Dispatch Loop Bit-Exact tests/cpp/vm_trace_test.cpp
tests/cpp/vm_determinism_property_test.cpp
tests/cpp/vm_tensor_get_set_conformance_test.cpp
tests/cpp/vm_state_transition_conformance_matrix_test.cpp		 Yes (ci.yml) Verified
Data Type Canonical Encoding Binary Format (Trit/Tryte) Bit-Exact tests/cpp/v1_canonical_numeric_contract_test.cpp
tests/cpp/tisc_binary_io_determinism_test.cpp		 Yes (ci.yml) Verified
Soft-Float Deterministic Math T81Float Operations Strict Rounding tests/cpp/test_T81Float_arithmetic.cpp
tests/cpp/test_T81Float_rounding.cpp		 Yes (ci.yml) Verified
Compiler Bytecode Emission T81Lang to TISC Bit-Exact (Fixtures) scripts/ci/t81lang_repro_gate.py Yes (repro-ledger.yml) Partial
T3K Quantization GGUF Encoding Bit-Exact scripts/ci/t3k_repro_gate.py Yes (repro-ledger.yml) Verified

3.1 Governing RFCs For Verified Surfaces

RFC Status Role
RFC-0042 accepted Scalar-oracle backend equivalence for scalar ↔ SWAR ↔ SIMD ↔ future backends
RFC-0043 accepted Common conformance, replay, breach-classification, and CI proof model
RFC-0044 accepted Stable packed-trit substrate beneath SWAR and SIMD surfaces
RFC-0045 accepted Canonical memory visibility, handle identity, and aliasing model
RFC-0046 accepted Program-order / dependency-order / canonical-commit scheduling constitution
RFC-0047 accepted Deterministic lowering and JIT constraints for alternate execution paths
RFC-0048 accepted DCP / governed non-DCP / experimental boundary constitution
RFC-0049 accepted Canonical arithmetic oracle for trit, packed, native, VM, and backend arithmetic
RFC-0050 accepted Semantic vector execution model at the ISA/VM layer
RFC-0051 accepted Heterogeneous acceleration rules for GPU and other accelerator backends
RFC-0052 accepted Canonical dataflow and state-driven propagation model above DPE
RFC-0053 accepted Distributed deterministic execution protocol for future cross-node execution
RFC-0054 accepted CanonFS object identity and persistence contract (payload-only hash rule)
RFC-0055 accepted Native ternary hardware target classification and interop governance

RFCs marked accepted are fully integrated and binding. Draft RFCs define governance direction but do not yet expand verified guarantees.

4. Non-Deterministic or Undefined Surfaces

Explicitly list areas that are:

Excluded / Out of Scope:

Experimental / Planned:

5. Verification Map

Surface Test Path CI Job Repro Script
TISC Execution tests/cpp/vm_determinism_property_test.cpp ci.yml N/A
VM Memory / State Determinism tests/cpp/vm_tensor_get_set_conformance_test.cpp
tests/cpp/vm_state_transition_conformance_matrix_test.cpp		 ci.yml (determinism-slice) N/A
Tritwise Backend Equivalence (RFC-0042) tests/cpp/test_tritwise_backend_equivalence.cpp — scalar vs SWAR vs AVX2/NEON, sizes 1–4097 trits ci.yml N/A
Arithmetic Backend Equivalence (RFC-0042 + RFC-0049) tests/cpp/test_arithmetic_backend_equivalence.cpp — scalar trit oracle vs T81BigInt for ADD/SUB/MUL/NEG/comparison/carry ci.yml N/A
Axion Epoch Runtime (scheduler + audit parity) experimental/ternaryos/tests/epoch_submission_test.cpp
experimental/ternaryos/tests/epoch_audit_test.cpp		 ci.yml (axion-epoch-determinism) N/A
Compiler Repro tests/fixtures/t81lang_determinism/*.t81 repro-ledger.yml scripts/ci/t81lang_repro_gate.py
Quantization N/A repro-ledger.yml scripts/ci/t3k_repro_gate.py

Proof model note:

Verified-surface claims are governed by RFC-0043 (Deterministic Conformance Validation Framework, accepted). The table above is the authoritative CI-enforced record. RFC-0043 §8 defines the promotion rules that every entry must satisfy before a surface may be marked Verified.

5.1 Conformance Layer Mapping (RFC-0043 §1)

Each verified surface maps to one or more RFC-0043 conformance layers:

Surface Semantic Backend Equiv Serialization Cross-Platform Gov Gate
TISC Execution Yes — — Yes Yes
VM Memory / State Yes — Yes Yes Yes
Tritwise Backend Equiv Yes Yes — Yes Yes
Arithmetic Backend Equiv Yes Yes — Yes Yes
Axion Epoch Runtime Yes — — Yes Yes
Compiler Repro — — Yes Yes Yes
Quantization — — Yes Yes Yes

5.2 Cross-Platform Replay Artifacts

The supported architecture set for the current major version is x86_64 + AArch64.

Architecture Kernel Compiler Backend Paths Active
x86_64 + AVX2 Linux / macOS Clang 18+ / GCC 14+ scalar, SWAR, AVX2 (≥ 64 B threshold)
AArch64 + NEON Linux / macOS AppleClang 17+ / Clang 18+ scalar, SWAR, NEON-OR (≥ 64 B threshold)

Replay succeeds only when all governed test binaries produce bit-identical pass/fail outcomes across both rows. Architecture-specific exclusions (NEON TNot/TAnd disabled) are documented in spec/tisc-spec.md §5.2.3 and do not constitute a divergence.

6. Breach Handling Reference

Reference:

Breach classification (per RFC-0043 §6):

State:

A regression on a verified surface is classified as a Hard Divergence (RFC-0043 §6) and must not be merged unresolved.

7. Scope Boundaries

Clarify:

Determinism does NOT mean:

Determinism governance DOES mean:

This prevents overclaim drift.

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