statecraft.
Catalog/rustev

047-target-independent-transcendentals

One implementation of exp and ln on every target (amends 002 and 027)

Lifecycle approvedImplementation completeVerification unknownQualification unknown

Approved (A-44). The remedy spec 027 3.11.5 names for a cross-target floating-point divergence. The pure crates' four transcendental call sites (`exp` in core's softmax, `ln` in core's calibration, `ln` in evaluation's log loss and temperature fit) call the platform's math library on native targets and Rust's bundled one on WebAssembly; measured on 2026-10-21 they differ by one unit in the last place on 0.08% to 7.1% of a million inputs per input domain (macOS arm64 against `wasm32-unknown-unknown`). This spec routes all four through one pure Rust implementation, the `libm` crate exact-pinned at 0.2.16 without default features, exposed as `rustev_core::math`, so each produces the same bits on every target; no existing golden changes. Ratified by the owner on 2026-10-21 (A-44). Approval does not authorize a release.

Read the full pinned specification ↗

Relationships

Claimed units

  • extends
    {
  "nature": "amending",
  "spec": "002-decision-contract-and-pure-core",
  "unit": {
    "kind": "directory",
    "path": "crates/rustev-core/"
  }
}
  • extends
    {
  "nature": "amending",
  "spec": "004-evaluation-and-replay",
  "unit": {
    "kind": "directory",
    "path": "crates/rustev-eval/"
  }
}
  • extends
    {
  "nature": "additive",
  "spec": "001-boundaries-and-authority",
  "unit": {
    "kind": "file",
    "path": "Cargo.toml"
  }
}
  • extends
    {
  "nature": "additive",
  "spec": "001-boundaries-and-authority",
  "unit": {
    "kind": "file",
    "path": "Cargo.lock"
  }
}
  • extends
    {
  "nature": "additive",
  "spec": "031-public-api-and-release-family",
  "unit": {
    "kind": "directory",
    "path": "tools/rustev-release/"
  }
}

Source headings

  1. 047: One implementation of exp and ln on every target (amends 002 and 027)
  2. 1. Purpose
  3. 2. Territory
  4. 3. One implementation
  5. What changes in spec 002
  6. What changes in spec 027
  7. 4. Out of scope
  8. 5. Observable negative cases
  9. Acceptance
  10. Verification
  11. Implementation record

Frozen anchors

No frozen anchors declared.