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//! hd128 FA-prefill twin gate (2026-07-07): the flash_attn.cu prefill kernels are
//! template-stamped at HEAD_DIM 256 (original names) and 128 (`_hd128`, the MiniMax-M3
//! class). This standalone microbench validates EVERY hd128 twin against the sdpa_naive
//! oracle at T up to 512, rel < 1e-2 (bf16-MMA class tolerance; the f32 twins measure
//! ~1e-3, the q8_0/q5_1 quant twins ride the same 6e-2 bound as kernel_check's hd256
//! rows — quantization noise, not the FA math). No model needed.
//!
//! fa_prefill_f32_pp_hd128 (default prefill) vs sdpa_naive @ hd128
//! fa_prefill_f32_hd128 (floor twin) vs sdpa_naive @ hd128
//! fa_prefill_q_hd128 (quant view) vs sdpa_naive @ hd128 (quant tol)
//! fa_prefill_qw/_db_hd128 (dequant-once ws twins) vs fa_prefill_q_hd128 BIT-IDENTITY
//!
//! Shapes: the generic (nh=16, nhkv=4) harness geometry at T=16..512 including
//! BK/BLOCK_Q-unaligned tails, plus the real M3 attention geometry (nh=64, nhkv=8).
//! hd256 rows re-run alongside to prove the stamped-256 dispatch is unchanged.
use memra_engine::Engine;
fn pr(i: usize) -> f32 {
(((i.wrapping_mul(2654435761)) >> 8) & 0xffff) as f32 / 32768.0 - 1.0
}
fn rel_diff(a: &[f32], b: &[f32]) -> f32 {
let d = a
.iter()
.zip(b)
.map(|(x, y)| (x - y).abs())
.fold(0.0f32, f32::max);
let s = a.iter().map(|v| v.abs()).fold(0.0f32, f32::max).max(1e-3);
d / s
}
fn main() -> Result<(), Box<dyn std::error::Error>> {
let e = Engine::new(0)?;
let mut fails = 0usize;
// (head_dim, n_head, n_head_kv, label)
let geoms = [
(128usize, 16usize, 4usize, "generic hd128"),
(128, 64, 8, "M3 hd128 (64h/8kv)"),
(256, 16, 4, "hd256 regression"),
];
// T cases: aligned, tail-unaligned (BLOCK_Q=64, BK=32), and the 512 gate bound.
let t_cases = [16usize, 64, 100, 256, 512];
for &(hd, nh, nhkv, label) in &geoms {
let scale = 1.0 / (hd as f32).sqrt();
for &t in &t_cases {
let tkv = t;
let q: Vec<f32> = (0..hd * nh * t).map(|i| pr(i) * 0.2).collect();
let k: Vec<f32> = (0..hd * nhkv * tkv).map(|i| pr(i + 7) * 0.2).collect();
let v: Vec<f32> = (0..hd * nhkv * tkv).map(|i| pr(i + 11) * 0.2).collect();
let qd = e.htod(&q)?;
let kd = e.htod(&k)?;
let vd = e.htod(&v)?;
// oracle: sdpa_naive (the current M3 bring-up path)
let mut o_ref = e.zeros(hd * nh * t)?;
e.sdpa_naive(&qd, &kd, &vd, &mut o_ref, hd, nh, nhkv, t, tkv, scale, true)?;
let oref = e.dtoh(&o_ref)?;
// 1) default prefill kernel (fa_prefill_f32_pp / _hd128)
let mut o_pp = e.zeros(hd * nh * t)?;
e.fa_prefill(&qd, &kd, &vd, &mut o_pp, hd, nh, nhkv, t, tkv, scale, true)?;
let rel = rel_diff(&oref, &e.dtoh(&o_pp)?);
println!(
"[{label}] fa_prefill(pp) T={t}: rel={rel:.2e} {}",
if rel < 1e-2 {
"OK"
} else {
fails += 1;
"FAIL"
}
);
// 2) floor twin (fa_prefill_f32 / _hd128) via MEMRA_FA_FLOOR
unsafe {
std::env::set_var("MEMRA_FA_FLOOR", "1");
}
let mut o_fl = e.zeros(hd * nh * t)?;
e.fa_prefill(&qd, &kd, &vd, &mut o_fl, hd, nh, nhkv, t, tkv, scale, true)?;
unsafe {
std::env::remove_var("MEMRA_FA_FLOOR");
}
let rel = rel_diff(&oref, &e.dtoh(&o_fl)?);
println!(
"[{label}] fa_prefill(flr) T={t}: rel={rel:.2e} {}",
if rel < 1e-2 {
"OK"
} else {
fails += 1;
"FAIL"
}
);
// 3) quant view twin (fa_prefill_q / _hd128): quantize K/V into a resident
// q8_0/q5_1 cache first. Tolerance = kernel_check's quant bound (6e-2).
let kv_dim = hd * nhkv;
let (kbb, vbb) = memra_engine::kv_blk_bytes(); // env-selected KV formats
let k_tok_bytes = (kv_dim / 32) * kbb;
let v_tok_bytes = (kv_dim / 32) * vbb;
let mut kc = e.alloc_u8(tkv * k_tok_bytes)?;
let mut vc = e.alloc_u8(tkv * v_tok_bytes)?;
for tok in 0..tkv {
let k_row = kd.slice(tok * kv_dim..(tok + 1) * kv_dim);
let v_row = vd.slice(tok * kv_dim..(tok + 1) * kv_dim);
e.append_kv_quantized_view(
&k_row,
&v_row,
&mut kc,
&mut vc,
tok,
kv_dim,
kv_dim,
k_tok_bytes,
v_tok_bytes,
false,
)?;
}
let kview = e.view_u8(&kc, tkv * k_tok_bytes);
let vview = e.view_u8(&vc, tkv * v_tok_bytes);
let mut o_q = e.zeros(hd * nh * t)?;
e.fa_prefill_view(
&qd,
&kview,
&vview,
&mut o_q,
hd,
nh,
nhkv,
t,
tkv,
scale,
true,
k_tok_bytes,
v_tok_bytes,
false,
)?;
let oq = e.dtoh(&o_q)?;
let rel = rel_diff(&oref, &oq);
println!(
"[{label}] fa_prefill_q T={t}: rel={rel:.2e} {}",
if rel < 6e-2 {
"OK"
} else {
fails += 1;
"FAIL"
}
);
// 4) dequant-once workspace twins (qw db-on and db-off): BIT-IDENTITY vs the
// inline-dequant kernel (the same contract kernel_check pins at hd256).
for db in ["1", "0"] {
unsafe {
std::env::set_var("MEMRA_PRIME_DEQW_DB", db);
}
let mut o_ws = e.zeros(hd * nh * t)?;
e.fa_prefill_view_ws(
&qd,
&kview,
&vview,
&mut o_ws,
hd,
nh,
nhkv,
t,
tkv,
scale,
true,
k_tok_bytes,
v_tok_bytes,
false,
)?;
let ows = e.dtoh(&o_ws)?;
let bitdiff = oq
.iter()
.zip(&ows)
.filter(|(x, y)| x.to_bits() != y.to_bits())
.count();
println!(
"[{label}] fa_prefill_qw(db={db}) T={t}: bitdiff={bitdiff} {}",
if bitdiff == 0 {
"OK"
} else {
fails += 1;
"FAIL"
}
);
}
unsafe {
std::env::remove_var("MEMRA_PRIME_DEQW_DB");
}
}
}
if fails == 0 {
println!("FA-HD128 GREEN");
} else {
println!("FA-HD128 FAIL ({fails})");
std::process::exit(1);
}
Ok(())
}