rajamesandClaude Opus 5.5
ab3b708540
Q.* is floor(a*b / 2^16), signed (D-8), cut to two cells. Cells 0..2 of the product come from the unsigned cell products a0*b0, a0*b1, a1*b0 and the low cell of a1*b1; reading a1 and b1 as signed takes (a1<0 ? b0 : 0) + (b1<0 ? a0 : 0) off cell 2. The result is cells 0..2 shifted right 16 with Q.TO-INT twice. Clobbers A. Checked at 32- and 64-bit cells, optimised and ASan+UBSan, on every pair of 17 edge Q values plus 20000 pseudo-random pairs: - against an independent reference (16-bit limbs, magnitudes multiplied schoolbook, negated, shifted), and - against v3's q48_mul for non-negative operands. The first draft applied only a1's sign correction; the reference caught the missing b1 term (9860 failures at 32-bit cells). v3 bug found, not fixed: q48_mul's portable branch (used where there is no __int128) returns (result_hi << 16) | (result_lo >> 16); the high part must move up 48, so it is wrong whenever the product passes bit 64, e.g. 0.5 * Q max gives 0000ffffffffffff instead of 3fffffffffffffff. The parity reference here is that branch with the shift corrected, which matches v3's __int128 branch. Stack use is tight: Q.* leaves its caller 2 data cells and 1 return entry, because UM* parks three values on the return stack. Recorded in 5.26; to be improved next. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
v4/
StarForth v4: the 32-instruction F18-derived core. The design lives in
docs/v4.0.0/JUSTIFICATION.md (why) and docs/v4.0.0/DECOMPOSITION.md
(every v3 word mapped to a v4 fate).
The first deliverable is the hosted C99 golden model (JUSTIFICATION.md §10,
step 1). It must pass POST and hold K≡1.0 with 32- and 64-bit cells on all
three host ISAs.
What exists so far is the single node: registers, circular stacks, memory, all
32 opcodes, and per-opcode and per-call-target heat. make -C v4 test builds
and runs the tests at both cell widths; make -C v4 sanitize repeats them
under ASan and UBSan. There is no compiler capsule, no POST and no K
measurement yet.