admin/LithosAnanake
1
1
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

feat(v4.0.0): D< and Q comparisons; call-free (D<), DMAX, DMIN, 2SWAP

Browse Source 
Executed on the golden model as written, and correct: <, =, D<, 2OVER,
and Q.=, Q.<, Q.0= (the D=, D<, D0= words).

Fixed, because they could not work under D-2 or were wrong:
- DMAX, DMIN: 2OVER 2OVER D< needs 8 data cells plus D<'s 2, the whole
  10-deep data stack, so both failed on every case once the caller held
  anything. Rewritten on a new call-free helper
    (D<) ( d1 d2 -- d1 d2 flag )
  which compares copies of the high cells, then the low cells unsigned
  on a tie, with in-line sign tests; DMAX and DMIN then drop the loser.
- 2SWAP: ROT and SWAP written in line. Return headroom 2 -> 4, which
  also lifts 2OVER 1 -> 3 and Q.> 1 -> 2.
- Q.>: section 5.26 gave SWAP D<, which swaps single cells; it was wrong
  in 11702 of 20169 cases. Now 2SWAP D<.

Checked at 32- and 64-bit cells, optimised and ASan+UBSan: every
edge-vector quadruple (50625) for D<, (D<), 2SWAP, 2OVER, DMAX and DMIN;
Q comparisons on every pair of 13 edge Q values plus 20000 pseudo-random
pairs weighted to ties and one-bit differences, signed (D-8) and against
v3's unsigned comparisons where both values have the same sign.
Mutating any (D<) branch or subtraction fails 700+ checks.

The new fatal-UBSan setting caught a test-side array overflow in the
headroom probe (results buffer sized 4, six needed); fixed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
rajames
2026-10-02 23:06:25 -04:00
co-authored by Claude Opus 5.5
parent 167fdc3973
commit d0accdbb88
2 changed files with 267 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files
docs/v4.0.0/DECOMPOSITION.md
+9 -8
View File
@@ -373,9 +373,9 @@ Section numbers match the v3 primitive reference.
| `0=` `0<` | CAP | §4 |
| `0<>` | CAP | `0= 0=` |
| `0>` | CAP | `dup 0< SWAP 0= OR 0=` (correct for the most negative number) |
| `=` | CAP | `xor 0=` |
| `=` | CAP | `xor 0=` — executed on the golden model (2026-10-02). |
| `<>` | CAP | `xor 0<>` |
| `<` | CAP | `2DUP xor 0< IF drop 0< ELSE - 0< THEN` (overflow-safe) |
| `<` | CAP | `2DUP xor 0< IF drop 0< ELSE - 0< THEN` (overflow-safe) — executed on the golden model (2026-10-02). |
| `>` | CAP | `SWAP <` |
| `<=` | CAP | `> 0=` |
| `>=` | CAP | `< 0=` |
@@ -412,15 +412,16 @@ A double is two 32-bit cells on a mesh node.
| `D0=` | CAP | `OR 0=` — executed on the golden model (2026-10-02). |
| `D0<` | CAP | `NIP 0<` |
| `D=` | CAP | `D- D0=` — executed on the golden model (2026-10-02). |
| `D<` | CAP | `ROT 2DUP = IF 2DROP U< ELSE SWAP < NIP NIP THEN` |
| `DMAX` | CAP | `2OVER 2OVER D< IF 2SWAP THEN 2DROP` |
| `DMIN` | CAP | `2OVER 2OVER D< 0= IF 2SWAP THEN 2DROP` |
| `D<` | CAP | `ROT 2DUP = IF 2DROP U< ELSE SWAP < NIP NIP THEN` — executed on the golden model (2026-10-02). |
| `(D<)` | CAP | `( d1 d2 -- d1 d2 flag )`, call-free; internal to `DMAX` and `DMIN`. Copies of the high cells go on top; if they differ the flag comes from them, else from the low cells unsigned. The value tested always has its top bit set exactly when `d1 < d2`: `ah` (high signs differ), `ah - bh` (agree), `bl` (low top bits differ), `al - bl` (agree); `x - y` with `y` on top is `push inv pop + inv`. `dup push push over pop over over xor if TIE drop over over xor -if HS drop drop jump S1 HS: drop push inv pop + inv S1: -if N1 drop -1 jump D1 N1: drop 0 D1: pop SWAP ; TIE: drop drop drop dup push push over pop over over xor -if LS drop NIP jump S2 LS: drop push inv pop + inv S2: -if N2 drop -1 jump D2 N2: drop 0 D2: pop pop ROT ;` with `SWAP`, `NIP` and `ROT` in line. Executed on the golden model (2026-10-02). |
| `DMAX` | CAP | `(D<) if L drop push push drop drop pop pop ; L: drop drop drop ;` Executed on the golden model (2026-10-02). Replaces `2OVER 2OVER D< IF 2SWAP THEN 2DROP`, which needs 8 data cells plus `D<`'s 2: the whole 10-deep data stack, so it failed whenever the caller held anything at all (D-2). |
| `DMIN` | CAP | `(D<) if L drop drop drop ; L: drop push push drop drop pop pop ;` Executed on the golden model (2026-10-02); replaces `2OVER 2OVER D< 0= IF 2SWAP THEN 2DROP` for the same reason as `DMAX`. |
| `D2*` | CAP | `2* over 0< NEGATE OR SWAP 2* SWAP` |
| `D2/` | CAP | `dup 1 and push 2/ SWAP 1 RSHIFT pop IF MSB OR THEN SWAP` |
| `2DROP` | IN | `drop drop` |
| `2DUP` | IN | `over over` |
| `2SWAP` | CAP | `ROT push ROT pop` |
| `2OVER` | CAP | `push push 2DUP pop pop 2SWAP` |
| `2SWAP` | CAP | `ROT push ROT pop`, with `ROT` and `SWAP` in line so it makes no calls. Executed on the golden model (2026-10-02). Called, `ROT` and `SWAP` left its caller 2 return entries; in line, 4. |
| `2OVER` | CAP | `push push 2DUP pop pop 2SWAP` — executed on the golden model (2026-10-02). |
| `2ROT` | CAP | `2>R 2SWAP 2R> 2SWAP` |
| `2>R` | IN | `SWAP push push` |
| `2R>` | IN | `pop pop SWAP` |
@@ -653,7 +654,7 @@ word. Per D-10 it occupies two cells on a 64-bit node too. Per D-8, v4 Q values
| `Q.FROM-INT` | CAP | `push 0 a! 0 pop 15 FOR +* UNEXT push drop a pop` — `n * 2^16` as a signed double. `+*` with `S = 0` never adds, so each step is an exact arithmetic right shift of `T:A`; starting from `T:A = n:0` (that is, `n * 2^N`) and shifting `N-16` bits leaves `n * 2^16`. The count is `N-17`: 15 at 32-bit cells, 47 at 64. Negative values are no longer clamped to 0. Executed on the golden model (2026-10-02): matches v3's `q48_from_u64` for `n >= 0` (at 64-bit cells in the low cell, where v3 wraps for `n >= 2^47`, per D-10). Clobbers `A`. |
| `Q.TO-INT` | CAP | `push a! 0 pop 15 FOR +* UNEXT drop drop a` — the same `+*` shift, 16 bits at every cell width, leaving the low cell in `A`. Rounds toward minus infinity, as v3's arithmetic shift does (−1.5 gives −2). Executed on the golden model (2026-10-02): v3's `q48_to_u64` exactly at 64-bit cells, its low cell at 32. Clobbers `A`. |
| `Q.1` `Q.0` `Q.SCALE` | IN | Double-cell constants. |
| `Q.=` `Q.<` `Q.>` `Q.0=` `Q.MAX` `Q.MIN` | CAP | `D=`, `D<`, `SWAP D<` (for `Q.>`), `D0=`, `DMAX`, `DMIN`. Signed. |
| `Q.=` `Q.<` `Q.>` `Q.0=` `Q.MAX` `Q.MIN` | CAP | `D=`, `D<`, `2SWAP D<` (for `Q.>`), `D0=`, `DMAX`, `DMIN`. Signed (D-8); v3 compared unsigned, so v3 agrees only when both values have the same sign. Executed on the golden model (2026-10-02). `Q.>` was given here as `SWAP D<`, which swaps single cells, not Q values, and gave a wrong answer in 11702 of 20169 test cases. |
| `Q.PRINT` | CAP | Pictured output, five fractional digits. |
### 5.27 Inference engine