notes: twiddle = 1024-entry sin table with stride sampling

2026-08-16 23:38:16 +03:00
parent 0d16c5f4b9
commit 00d8623b92
4 changed files with 361 additions and 48 deletions
@@ -49,4 +49,9 @@ outer while (uVar24 < (iVar25-1+iVar33)/iVar33)
  structure; different base-call FUN_18002e360 vs FUN_180023860).
 - Stage kernels executed at runtime are the dispatched vector kernels (see roadmap),
  driven from this plan's ordering; the transform itself therefore reproduces a
-  specific FFT: split-radix 2/4/8-style in-place butterflies with fused reorder.
+  specific FFT: split-radix 2/4/8-style in-place butterflies with fused reorder.
+## Twiddle source (DAT_182616800 = sin-table)
+- 1024 doubles = exact sin(k*2*pi/1024) (double precision), first half-period 0..512 (rest garbage of neighboring data).
+- Copied to scratch by FUN_180039b00( log2N, dst ): step lVar18 = 1 << (10 - log2N) for N<=1024.
+- So for N = 2^m: twiddle angles sampled from table with stride 2^(10-m). For N>1024 separate (two-pass) branch (unresolved).
+- Stage kernels (FUN_18000bfc0/18000c5e0) consume these with 0x40-complex chunks, cplx-mul=180008440, acc=FUN_1800437c0/180044700.