# SPDX-License-Identifier: AGPL-3.0-or-later
# Copyright (C) 2026 David (Corey) Herrera
# matmul_float16b.cbtable
#   The bf16 matmul's CB contract, and the file that makes MATH_FIDELITY a CHOICE.
#
#   Three CBs, all Float16_b 2048 B:
#     cb  0  activations
#     cb  1  weights
#     cb 16  output
#
#   Until 2026-08-12 the bf16 matmul named no CB table at all, so it inherited
#   build_tensix_kernel.sh's uniform-legacy set — which is where MATH_FIDELITY = 4 came
#   from. Nobody chose it. That mattered because a fidelity level is a MULTIPLIER on the
#   matmul's math cycles: the matmul MOP's inner loop count is set to the
#   fidelity value, so a 32x32x32 matmul_tiles is 16 cycles at LoFi and 64 at HiFi4
#   (GEMM_FLOPS.md:107). The descriptor content is otherwise identical to the legacy set
#   for the three CBs this kernel uses; the unused ones become Invalid, which nothing
#   reads.
#
#   THE FIDELITY DECISION IS HiFi4, AND IT IS NOT A TRADE. Swept at LoFi / HiFi2 / HiFi3 /
#   HiFi4 against the whole Phase 4 PCC suite: a 4x arithmetic difference moved wall time
#   by 0.6%, inside the run-to-run spread, because the matmul is data-movement bound at
#   every depth — one tile is 64 cycles = 80 ns at HiFi4 and the reader delivers a pair
#   every 104 ns. With no throughput to gain, the choice is on accuracy alone, and HiFi4 is
#   the level with the a-priori guarantee (more mantissa bits per product).
#   Full PCC and max-abs tables, including the unexplained result that LoFi measures BETTER on the long-K shapes: docs/tt_bringup_log.md §16.3.
#
#   Format: tools/emit_tensix_cb_formats.py
#   cb <index> <format> <tile_r> <tile_c> <face_r> <num_faces>

math_fidelity  4
approx         0
dst_accum_mode 1
# ---------------------------------------------------------------------------
# Flipped 0 -> 1 on 2026-08-13, and it should have happened months earlier.
# ---------------------------------------------------------------------------
# §19 MEASURED this on THIS kernel and these shapes: ffn_down max-abs 2.187 -> 0.0626
# (35x), PCC 0.998878 -> 0.999999, and 473.3 -> 473.4 GFLOP/s -- i.e. free, because the
# op is data-movement bound and the accumulator costs nothing. §19's own conclusion was
# "Ship it."
#
# It was then applied to every op written AFTERWARDS -- eltwise, reduce, rope, topk,
# attention all default to 1 -- and never back-ported to the kernel it was measured on.
# So the single highest accuracy-per-cost finding in this project was live everywhere
# except its own subject. Found by an upstream-comparison round noticing that the two
# DEEPEST accumulation chains were the two still running a 16-bit accumulator.
#
# The two block-float tables followed on 2026-08-13, on their OWN on-card measurement
# rather than on this one -- §19's caveat was bf16-in/bf16-out and it was honoured. Their
# numbers, and the Phase 4 "BFP4 beats BFP8" question they close, are in
# matmul_bfp4_b.cbtable. Nothing in this family now runs a 16-bit accumulator. Free at
# scale is measured for THIS table: Mt=32 gives 631.0 GFLOP/s at PCC 0.999999, so the
# halved DST tile capacity does not bind.

cb  0  Float16_b 32 32 16 4
cb  1  Float16_b 32 32 16 4
cb 16  Float16_b 32 32 16 4