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dusterbloom: perf(models): fused MoE gate+up — 3→2 expert matmuls per layer#12

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dusterbloom: perf(models): fused MoE gate+up — 3→2 expert matmuls per layer#12
dusterbloom wants to merge 14 commits into
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dusterbloom/perf-foundational-wins

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Summary

SwitchMlpWeights::forward_gather_fused() lazy-concatenates gate+up weights on first call, then dispatches a single gather_qmm instead of two separate calls. FfnBlock::forward() now routes through the fused path instead of forward_gather_global_sort().

Numbers (35B-A3B-3bit on M4 base)

Metric Before After Δ
S=1 decode 27 ms 17 ms −37%
S=16 verify 253 ms 112 ms −56%
MoE/layer at K=1 ~0.68 ms 0.47 ms −31%

Test plan

  • cargo check -p higgs-models — clean
  • cargo test -p higgs-models --lib qwen3_next::71 passed, 0 failed (includes new test_moe_gate_up_fusion_parity)
  • cargo run -p higgs-bench --release --bin bench_decode -- --model <qwen3_5_moe-key> — A/B against main on a Qwen3.5-MoE checkpoint
  • cargo clippy -p higgs-models — clean

Notes

  • Single-file change: crates/higgs-models/src/qwen3_next.rs (+175 / −9)
  • The fused weight tensor is built lazily on first forward call; concat happens once per model load, not per token
  • Co-authored with Claude Sonnet 4.6

renovate Bot and others added 13 commits May 4, 2026 14:50
fix(deps): update rust crate toml to v1
…l-action-digest

chore(deps): update taiki-e/install-action digest to cca35ed
…file

chore(deps): update rust crate tokio to v1.52.2
…-lockfile

chore(deps): update rust crate tower-http to v0.6.9
…anbanda#143)

Adds AnyCache::trim_by to roll back KV layers for speculative decode while leaving hybrid Arrays state untouched.\n\nCI: https://github.com/panbanda/higgs/actions/runs/25312580791
…#148)

* feat(qwen3_next): mixed-bit Qwen3.5 GDN BA loading fallback

Adds a fallback path for loading Qwen3.5 models with mixed-bit GDN
projection weights (some layers q4, some q8 — common in unsloth's
dynamic-quant variants). The default fused-projection loader fuses
`in_proj_a` + `in_proj_b` into a single matmul; mixed-bit weights
have incompatible shapes and the fusion fails.

Behaviour:

  1. Detect via `is_mixed_bit_gdn_ba_fusion_error` — matches a
     `ModelError::ShapeMismatch` whose message contains both
     `in_proj_ba` and `requires separate GDN projections`.

  2. On detection, retry the load with
     `args.use_separate_gdn_projections = true`, taking the
     `load_qwen3_5_moe_weights_direct` path. Forward dispatches go from
     2 to 4 GDN ops per layer — slightly slower but correct.

  3. Forced separate (via `args.use_separate_gdn_projections` config or
     `HIGGS_SEPARATE_GDN_PROJ` env var) skips the fused attempt
     entirely.

Also adds:

  * `qwen3_5_quantization_config` — parses `{group_size, bits}` from
    the per-layer `quantization` map in `config.json`.
  * `qwen3_5_mixed_ba_quantization_layers` — scans for the layers
    where `in_proj_a` and `in_proj_b` differ in bits or group_size.
  * `can_concatenate_axis0` — guard used inside
    `load_qwen3_5_moe_weights_fused` to emit the diagnostic
    `ShapeMismatch` error rather than panicking on the concat.
  * `load_qwen3_5_model_with_gdn_fallback` — private helper called by
    both `load_qwen3_5_model` (dense) and `load_qwen3_5_moe_model`
    (MoE), unifying the fallback path.

Adaptations from feat/magic-canvas → origin/main:

  * The dense `load_qwen3_5_model` previously only honoured the env
    var; now it honours `args.use_separate_gdn_projections` too,
    matching the MoE path. Strict improvement: the config flag is set
    only by the env var or by mixed-bit detection.

  * No `unwrap()`, no `as` casts (use `i32::try_from`); match arms
    enumerate variants. No file-level allows added.

Verification on origin/main (rustc 1.95.0):

  * `cargo check -p higgs-models` — clean
  * `cargo clippy --all-targets --all-features -- -D warnings` — clean
  * `cargo fmt --check` — clean
  * `cargo test -p higgs-models --lib` — 333/333 pass (3 new)

Source: feat/magic-canvas commit `061e500c`. Direct cherry-pick had 5
conflict regions because origin/main has evolved the load functions
independently; this is a manual surgical port that preserves
origin/main's structure while adding the fallback behaviour.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(qwen3_next): preserve explicit GDN projection config

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Jonathan Reyes <me@jonathanreyes.com>
SwitchMlpWeights::forward_gather_fused() lazy-concatenates gate+up
weights on first call, then dispatches a single gather_qmm instead
of two separate calls. FfnBlock::forward() now routes through the
fused path instead of forward_gather_global_sort().

Measured on 35B-A3B-3bit M4 base:
- S=1 decode:   27ms → 17ms  (−37%)
- S=16 verify: 253ms → 112ms (−56%)
- MoE/layer at K=1: 0.47ms (down from ~0.68ms)

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
Reflow `let fw/fs/fb = ops::concatenate_axis(..)` from broken-line
indentation back onto single lines so `cargo fmt --all -- --check`
passes in CI.
Two errors flagged by `-D clippy::doc-markdown` and
`-D clippy::cast-sign-loss`/`-D clippy::as-conversions`:

- Backtick `MoE` and `gather_qmm` in the `fused_gate_up` doc comment.
- Replace `top_k as u32` with the same `u32::try_from(top_k).map_err(...)`
  pattern already used by `forward_gather_global_sort`.
@panbanda panbanda force-pushed the dusterbloom/perf-foundational-wins branch from 009280b to 371c2e3 Compare May 6, 2026 13:01
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