argsort_f32_i32_cuda_cub called the one-shot DeviceRadixSort::SortPairs
API with d_keys_in == d_keys_out (temp_keys, temp_keys). CUB's internal
double-buffer ping-pong requires distinct key buffers: with aliased
buffers the sort partially overwrites its own input mid-pass and emits a
corrupted permutation, surfacing as intermittent garbage indices (e.g.
backend top_k over a 248k-column vocab on Maxwell/CUDA 12.5/CCCL 2.x,
which then triggered out-of-bounds gathers in downstream get_rows).
Use a distinct keys-out buffer for all six call sites (plain and
segmented, ascending and descending, size-query and execute).
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Oliver Simons <osimons@nvidia.com>
Allow HMX flash-attention to run with head_dim not a multiple of 64
(e.g. SigLIP head_dim=72), by operating on DK/DV rounded up to 64 with
zero-filled tail lanes.
* ggml-cpu: add F16 input to the FWHT
The CPU FWHT accepts F32 input only. This change makes the source type a
template parameter. The CPU path now accepts F16 input and F32 input.
The CPU MUL_MAT reference now converts an F16 src1 to F32. It does this when
the caller sets the Hadamard hint.
No backend has an F16 FWHT kernel yet. The test cases come with the backend
changes that add one.
* ggml-cpu: assert the F16 FWHT input path, and use the bulk converter
Address review feedback.
The F16 branch writes plain floats into wdata, which is only correct when
vec_dot_type is F32. That invariant held because supports_op only accepts an
F16 src1 for the Hadamard hint with F32 src0 and dst, but nothing enforced it.
Assert it next to the existing src1 type check so widening supports_op cannot
silently break the write.
Replace the hand-rolled conversion loop with ggml_cpu_fp16_to_fp32.
* vulkan: add IQ3_S MMQ matmul kernels
* Make block_a_to_shmem do 2-byte loads (110 bytes is divisible by 2)
* Align the check, IQ3_S is also using K tile size
* vulkan: raise the hoisted row-id limit for mul_mat_id to 512 experts
The expert-count shader (count_experts.comp) sizes its shared arrays
with BLOCK_SIZE, which is 256. Because of that, row-id hoisting is
switched off for any model with more than 256 experts, and every
mul_mat_id workgroup has to rescan the whole ids tensor on its own.
Qwen3.8-Flash-Next has 512 experts and was quietly running on that
slow path.
This change sizes the arrays with a separate MAX_EXPERTS constant (512),
clears them in a loop instead of one entry per thread, and raises the
matching limit on the host side.
On Strix Halo at batch 2048 the expert matmuls drop from 12.5 to 9.5 ms
(iq3_s) and from 14.0 to 7.5 ms (iq4_nl) per op, and prompt processing
gets about 19 % faster at 8k tokens. test-backend-ops MUL_MAT_ID passes
(891/891) with new 512-expert test cases.
Assisted-by: Claude Fable 5.1
* vulkan: raise the hoisted row-id limit for mul_mat_id to 1024 experts
Follow-up to review feedback: 1024 matches LLAMA_MAX_EXPERTS instead of
stopping at 512. The three shared arrays in count_experts.comp grow to
3 * 1024 * 4 = 12 KiB, which fits the 16 KiB that Vulkan guarantees for
maxComputeSharedMemorySize.
Adds mul_mat_id test cases at 1024 experts alongside the existing 512
ones. test-backend-ops MUL_MAT_ID passes on Vulkan (RADV, Strix Halo,
Radeon 8060S): 889/889.
* Update to openvino-2026.4
* Update OV docs
* ggml-openvino : fix clangd and MSVC warnings
* fix int to ptr cast, more internal linkage enforcement, and avoiding duplicate switch case
---------
Co-authored-by: Mostafa Faheem <mostafaaafaheem@gmail.com>
* gguf : align the data section relative to the GGUF start, not the file
gguf_init_from_file_ptr reads a GGUF from the current file position, but padded
the data section from file offset 0, so a GGUF embedded at an offset that is not
a multiple of the alignment loaded without error and returned wrong tensor data.
Also adds llama_adapter_lora_init_from_file_ptr, and disables mmap with a warning
when an embedded data section is not aligned, instead of asserting in ggml.
Assisted-by: Claude Opus 5
* llama : load lora from path through the FILE* variant
The test now checks that mmap is disabled only for an unaligned offset.
Assisted-by: Claude Fable 5.1
* Update ggml/src/gguf.cpp
Co-authored-by: Johannes Gäßler <johannesg@5d6.de>
* Update include/llama.h
Co-authored-by: Johannes Gäßler <johannesg@5d6.de>
* llama : error on unaligned mmap of an embedded GGUF, drop test-load-file-ptr
---------
Co-authored-by: Johannes Gäßler <johannesg@5d6.de>
Both im2col.comp and im2col_3d.comp declare D_ptr without an explicit
buffer_reference_align, so glslang emits writes through it as Aligned
16. The shaders advance the pointer by D_SIZE, a per-variant define
set to 4 for float and 2 for float16_t, so most write addresses are
not 16-byte aligned. This triggers
VUID-RuntimeSpirv-PhysicalStorageBuffer64-06315 under GPU-AV.
Declaring buffer_reference_align = D_SIZE matches the alignment to the
actual write stride and takes validation hits from 20 to 0 for both
IM2COL and IM2COL_3D.
Fixes#28960
llama probes weight placement with a rope where all params are 0, so rejecting
n_dims == 0 or freq_base == 0 puts rope_freqs on the CPU. That splits the decode
graph at every full-attention layer (gemma-4-E2B: 5 splits instead of 2).
Assisted-by: Claude Opus 5
The `sizeof(int16_t)` branch in `permute_transpose_impl` calls
`rvv_transposed_s32_mn_to_nm` instead of `rvv_transposed_s16_mn_to_nm`.
This is a copy-paste bug from the `sizeof(int32_t)` branch above it.
The s32 function uses 32-bit segment load/stores (`vssseg8e32.v`) on 16-bit
data, reading 2x bytes per element and producing completely wrong
transposition results -- 14 out of 16 positions are corrupted for a 4x4
int16 matrix.
The correct function `rvv_transposed_s16_mn_to_nm` already exists (line 390)
and is used elsewhere in flash attention (line 1488).
The server caches the most recent compute graph per device so that
GRAPH_RECOMPUTE can re-execute it without resending tensor data. The
cached graph nodes hold direct pointers to backend buffers that were
live at graph_compute() time. If any of those buffers is later
released via FREE_BUFFER, the next GRAPH_RECOMPUTE re-executes the
cached graph through the dangling pointers (use-after-free).
The bug is reachable by an unauthenticated remote client. The
dangling pointers point into chunks an attacker can reshape via
subsequent ALLOC_BUFFER/SET_TENSOR commands, and the resulting
read/write through the cached graph is sufficient to leak libc
addresses and hijack the buffer iface vtable used by BUFFER_CLEAR,
yielding remote code execution.
Discard all cached graphs in free_buffer(). The existing null-check
in graph_recompute() then rejects the request and the client falls
back to GRAPH_COMPUTE on the next call.
No protocol or API change.
It's found the MoE ncols_opt tile heuristic needs to be broadened
to include the RDNA3.5 architecture.
The code change is implemented in ggml/src/ggml-cuda/mmq.cu
and just change the GGML_CUDA_CC_IS_RDNA3_0 to
GGML_CUDA_CC_IS_RDNA3 in the condition.
The dense dispatch logic remains unchanged.
The Test machine configuration we used is
AMD Radeon 8060S, gfx1151 (RDNA3.5), 20 CU, wave32
+ AMD Ryzen AI MAX+ 388, 8C/16T, 23.79 GB RAM
we complete the Correctness verification and performance evaluation as follows:
test-backend-ops test -b ROCm0 -o MUL_MAT -p type_a=<q4_K|q5_K|q4_0|q5_0>
test-backend-ops test -b ROCm0 -o MUL_MAT_ID -p type_a=<q4_K|q5_K|q4_0|q5_0>
all pass: MUL_MAT 64/64, 29/29, 48/48, 14/14;
MUL_MAT_ID 84/84, 3/3, 74/74, 3/3
Performance result on target machine:
LFM2.5-8B-A1B-UD-Q4_K_M (Q4_K MoE) +16.198% [+12.704, +19.799] 8/8
Qwen1.5-MoE-A2.7B-Q2_K (Q2_K MoE) +6.189% [ +5.245, +7.141] 8/8
pooled (16 pairs) +11.081% [ +7.972, +14.279] 16/16
Token generation (tg128) is unchanged on the Q4_K MoE model and +2.188%
[+0.905, +3.488] on the Q2_K one.
Use BN/2 as the default for BNover2 and as the disabled fallback for BNover4, and remove the enable gate from the MUL_MAT_ID BN/2 branch. The BN/4 branch remains gated by enable_smaller_matrices, while the p.N path is unchanged.
* test-backend-ops: reproduce MUL_MAT_ID NaN for activations beyond f16
The Metal mul_mm_id path narrows src1 to `half` for the simdgroup MMA
(`S1 = half` in every instantiation; ggml-metal.metal:10582 and :10595,
mirrored at :10643/:10654 in the tensor-ops path). f16 saturates at
65504, so a model whose activations exceed that produces inf, and
`simdgroup_multiply_accumulate` then turns the whole 8x8 accumulator
tile into NaN. The mul_mv_id path used below `ne21_mm_id_min` (32)
carries the same values in f32 and is correct, as is every CPU path.
This was untestable before: `init_mul_mat_id_tensors` initializes
uniform [-1, 1], so no existing case can drive an operand out of f16
range. `test_mul_mat_id` gains an `amax` parameter (default 1.0f,
preserving the historical init exactly) that scales only the f32
activations, leaving the quantized weights in their normal range.
Six cases: n=16 sits below the mul_mv_id -> mul_mm_id switch and is the
control that must stay green; n=32 and n=64 are above it and fail on
Metal today. Two shapes, because this is not model- or size-specific —
q4_K at 128 experts / 4 active / 4096x2048 mirrors a real model, and
q8_0 at 8 experts / 2 active / 512x256 shows the same failure at
minimal size.
Observed on Apple M2 Max, macOS, llama.cpp b10156:
MUL_MAT_ID(type_a=q8_0,...,n=32,k=256,amax=100000.000000):
[MUL_MAT_ID] NaN at index 0 (MTL0=nan CPU=583442.375000) FAIL
The real model behind this is Mistral Small 4 (arch mistral4, 128
experts / 4 active), one of whose layers reaches ~1e5 activations: on
Metal every prefill of >=32 tokens returns an entirely NaN vocabulary,
while <32 tokens is correct.
Note kernel_mul_mm (dense) has the identical conversion at :10273 and
:10286 and is expected to fail the same way; it is not covered here.
Found and written by Claude Opus 5 (via Claude Code).
* metal: fix NaN in mul_mm_id when activations exceed f16 range
kernel_mul_mm_id narrows src1 to `half` for the simdgroup MMA operands
(`S1 = half` in every instantiation). f16 saturates at 65504, so a model
whose activations exceed that produces inf on load, and
simdgroup_multiply_accumulate then propagates NaN across the whole 8x8
accumulator tile. The result is an entirely NaN output — not a precision
loss, a total loss. The mul_mv_id path taken below ne21_mm_id_min (32)
keeps the same values in f32 and is correct, as is every CPU path, so
the same model produces correct logits for short inputs and NaN for
long ones.
Fix: rescale src1 by a power of two so it fits, and undo the scale on
the f32 accumulator at the store. A two-stage reduction computes
max(|src1|) and writes the pair (1/scale, scale) into scratch chained
off the destination buffer, in the same style as the existing tpe/ids
id-mapping scratch. The matmul multiplies on load and on store.
This is exact, not approximate, for two reasons: the dot product is
linear, so one tensor-wide factor commutes through the accumulation;
and the factor is a power of two, so both multiplications are exact in
binary floating point. When max(|src1|) already fits — every model that
works today — the factor is exactly 1.0 and the output is bit-identical
to before. Accumulation was already f32 and is unchanged; only the
operand narrowing was ever the problem.
The reduction is two-stage (256 threadgroups into partials, then one
threadgroup folding them) specifically so it stays bandwidth-bound. A
single-threadgroup version was measured first and cost up to +451%
median on prefill — the scan serialized against an otherwise idle GPU.
It is also dispatched only on the mm path, so decode never pays for it.
Measured on Apple M2 Max, `test-backend-ops perf -o MUL_MAT_ID -b MTL0`,
99 cases, versus the same build without this change:
n=1/4/8 (mul_mv_id, decode) : -0.8% / -0.8% / -0.4% median (noise)
n=32 (mul_mm_id, prefill) : +1.73% median
n=64 : +1.30% median
n=128 : +1.80% median
n=256 : +3.98% median
n=512 : +3.74% median, +7.20% worst
overall : +1.14% median
Correctness, same machine:
- the six new test-backend-ops cases go from 4 FAIL / 2 OK to all OK,
with the n=16 controls (mul_mv_id path) unchanged;
- `test-backend-ops -b MTL0` full run: 0 failures, no regression;
- Mistral-Small-4-119B (arch mistral4, 128 experts / 4 active) now
generates correctly at the default n_ubatch of 512, in both
UD-IQ3_S and UD-Q4_K_XL quantizations. Before this, every prefill of
>= 32 tokens returned an all-NaN vocabulary and only n_ubatch <= 31
(forcing the mul_mv_id path) worked.
Likely fixes#25722 (mistral4 empty output on Metal above ~300 tokens,
FA on and off, generation degenerating to a single control token — the
signature of argmax over an all-NaN distribution). #20668 may be the
same defect attributed to a bad GGUF.
Note kernel_mul_mm (dense) has the identical narrowing at the
corresponding load sites and is expected to fail the same way; it is
left alone here to keep this change reviewable. Also possible, and left
for later: scaling per output column rather than per tensor, which
would preserve more precision when a single token is the hot one.
Found, diagnosed and fixed by Claude Opus 5 (via Claude Code).
* metal : make requested edits
- remove verbose comments
- explain rationale as requested
Generative AI disclosure: Claude made the edits as requested.
* metal : stack mul_mm_id map0 with amax_part
Implement @ggerganov suggestion to stack amax_part + map0. Mean 2.6% faster (worst -0.7%, best -4.1%). Win grows with batch size. Benchmarked on a hot M2 Max after reboot.
Generative AI disclosure:
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
* cont : fix var scope
* cont : comment out tests temporarily
Comment out tess to not break CI temporarily
Assisted-by: Claude Fable 5.1
---------
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
* rpc : hash-cache only weights
ggml_backend_rpc_buffer_set_tensor and ggml_backend_rpc_set_tensor_async
hashed every transfer above HASH_THRESHOLD and let `rpc-server -c` serve it
from its file cache. The cache is meant for weights, but the activations
ggml_backend_sched copies between backends took the same path: with a
two-node split of Qwen3.8-Flash-Next every prefill ubatch above 10 MB was
hashed, written to the worker's cache directory (1.4 TB after a day) and
later served from there. Use the hash path only for tensors in buffers
marked GGML_BACKEND_BUFFER_USAGE_WEIGHTS.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
* rpc : save a cache entry only for the tensor that missed the hash check
With the client hashing weights only, the server still wrote every
SET_TENSOR above HASH_THRESHOLD to the cache directory, so the compute
data the scheduler sends kept filling the disk. Remember the hash of the
last SET_TENSOR_HASH that missed and save only the SET_TENSOR that
follows it with that hash - the weight the client is re-sending.
* rpc : signal the cache decision in the SET_TENSOR payload
Replace the server-side `pending_cache` state with a `cache_flag` byte
in the SET_TENSOR message: the client sets it when SET_TENSOR_HASH
reported a miss, the server saves a cache entry only when it is set.
Bump RPC_PROTO_MAJOR_VERSION since the wire format changes.
---------
Co-authored-by: Patrick Hoffmann <patrickhoffmann@MacBook-Pro-14-HOP.local>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
* cuda: support row-contiguous SUM_ROWS
* organize the code and add GGML_OP_MEAN to support row-contiguous tensors using the same shared kernel, and add a test to MEAN permute/slice
* Keep original comments and add if/else branch
* exclude GPU/NPU failing POOL_2D case
* Fix pool case
* ggml-openvino: fix stateful decode for Gemma-4 per-layer-type head sizes
* ggml-openvino: fix MSVC narrowing error in permute
* ggml-openvino: classify sliding-window layers structurally on interleaved-SWA models
* ggml-openvino: add GGML_OPENVINO_REQUANT_KQUANT to select a 4-bit requant target
* ggml-openvino: add GGML_OPENVINO_SPILL_DIR to spill weight buffers to disk
* Stateful Performance: Added pass::KVStateSeqAxis to change KV layout
* ggml-openvino: fix stateful decode past the sliding-window size
Assisted-by: Claude Sonnet
* ggml-openvino: refuse stateful decode that cannot resume from the KV state
The stateful path seeds its KV state from ggml's cache when the decode position
is ahead of what the state holds. That only works when ggml's cache is a plain
prefix, where cell i holds position i. A sliding-window layer keeps just the last
n_swa positions and drops the rest, so past the window cell i no longer holds
position i and the seeded state is wrong.
Slicing the state to the decode position also had no bounds check, so a position
past the end surfaced as a bare ov::Exception from the ROI constructor
(llama_decode ret = -3, with no reason given at default verbosity).
Refuse both cases with a clear message instead, and refuse on the compile path
too, where a new model starts with an empty state and so can only serve a
sequence from its beginning. Reproducible with llama-bench -d, which restores a
saved sequence state rather than recomputing the depth prefill.
Assisted-by: Claude Opus 5
* ggml-openvino: use the per-layer KV head count for the stateful KV state
The stateful path reinterprets ggml's KV buffer [1, 1, seq, n_heads_kv * head_size]
as [1, seq, n_heads_kv, head_size]. The head size is already taken from the
tensor's own combined dim, because gemma-4 varies it per layer type, but the head
count still came from a model-level scalar that compute_llm_params() overwrites
per attention node, so it ended up holding whatever the last layer said.
gemma-4 varies the head count per layer too: 12B has 8 x 256 sliding layers and
1 x 512 full layers, 31B has 16 x 256 and 4 x 512. So 40 of 12B's 48 layers were
split as 1 x 2048 instead of 8 x 256, and attention read the state with the wrong
head split - both models decoded garbage on CPU and GPU. E2B is unaffected, its
head count is 1 everywhere.
Record the count per layer instead and look it up by the cache_k_l<N> leaf name.
Key it by layer, not by layer type: the sliding/full classification comes from
cache extents, which tie at a small -c, while the head count does not.
The stateful state trim now derives its sequence axis per state for the same
reason, since pass::KVStateSeqAxis matches per state on the head count.
Assisted-by: Claude Opus 5
* ggml-openvino: apply the KV state relayout to any KV head count
pass::KVStateSeqAxis was limited to states with a single KV head, where moving
the sequence axis from dim 1 to dim 2 is a pure metadata change. The limit was
also based on a measurement showing no gain for a multi-head model, but that was
taken at depth 0, which is the one depth where this change does nothing.
With several heads the pass does more than move metadata: it drops the reader
side transpose of the whole accumulated state, which the graph otherwise redoes
every token at a cost that grows with the context length, and replaces it with a
transpose of the single new row. Measured on GPU, tg128, alternating arms:
gemma-4-12B 6.27 -> 9.11 t/s at depth 8192 (stateless is 7.69, so stateful now
wins at depth instead of losing), Llama-3.2-1B 47.8 -> 59.6 t/s. Both are within
noise at depth 0, which is why the earlier check saw nothing.
The state refill needs the rows copied rather than reinterpreted now: ggml stores
[seq][n_heads_kv * head_size], and a relayout state with several heads is a
different element order. Without that, a refill would seed wrong data - it is
reachable today through llama-bench -d.
Assisted-by: Claude Opus 5
* ggml-openvino : support ggml_rope_set_offset and simplify op support gating
* add more cpy cases
* reject BF16 cpy on NPU
* Remove mul_mat_id fallback, gate large mul_mat_id only for mxfp4
* ggml-openvino: fuse the MoE expert block into MOECompressed on GPU
* ggml-openvino: skip GPU MUL_MAT_ID for unbound expert tensors
* ggml-openvino: requantize grouped 8-bit MoE experts on GPU
* Enable special strided CPY for conv state writeback
* openvino: support cacheless encoder models on NPU
Packed QKV views used by mmBERT were rejected by the ROPE support check. This split Q/K RoPE onto CPU, prevented cacheless attention detection, and sent fragmented encoder graphs through the decoder-oriented NPUW path.
Accept packed QKV RoPE views, detect cacheless attention from its mask, and run these models as a single full-sequence prefill without NPUW or a decode graph. Also provide static mask, output index, and mean-pooling shapes and inputs.
* openvino: optimize norm and RoPE translation
Replace the decomposed mean/variance normalization graph with an opset6 MVN operation. This preserves the GGML epsilon placement while allowing OpenVINO plugins to compile normalization as one operation with fewer intermediate tensors.
Cache RoPE sine and cosine outputs in the graph-wide tensor map. Build the cache key from all RoPE parameters and the optional frequency-factor input so compatible Q/K and layer nodes share one subgraph without mixing different RoPE configurations.
Expose NodeContext::put_shared() to publish translator-created outputs for graph-level reuse.
* ggml-openvino : simplify op translators and enable IMROPE/NEOX RoPE fusion
* remove unnecessary include and clean up PAD
* fix mulmat bug
* use ov::as_type_ptr instead of std::dynamic_pointer_cast
* ggml-openvino: fix mixed-dtype ADD/SWIGLU_CLAMP, gate unsupported ROPE/SOFTPLUS cases
- translate_add: upcast mismatched operand types (e.g. f16/f32 in fused
ADD_ADD) to f32, add, then cast once to the output type. opset1::Add
requires matching input types and downcasting first lost precision.
- translate_glu_swiglu_clamp: same fix, f16 Swish/Clamp rounding was
drifting past the test tolerance.
- supports_op: reject ROPE with ne[3] > 1 (multi-sequence) since the
cos/sin tables only cover one sequence, and SOFTPLUS on GPU since the
OpenVINO GPU kernel overflows to inf for large inputs (CPU is fine).
- ci/run.sh: serialize test-backend-ops on OpenVINO GPU; running two
workers concurrently crashes the GPU plugin (CL_OUT_OF_RESOURCES).
* openvino: share compiled models with per-context inference state; fix thread-safety
* ggml-openvino: gate MoE expert-sum ReduceSum shortcut past 8 experts
The ReduceSum shortcut for the MoE expert-plane-sum ADD chain drifts past
the 1e-7 test tolerance for >8 experts (f32 accumulation order vs CPU
reference), intermittently, like the existing Q4_K/Q5_K NMSE case.
Expose is_moe_expert_sum_add() so supports_op can gate on expert count
and fall back to CPU for just that reduction op.
* ggml-openvino: gate degenerate m=1,n=1 MUL_MAT on GPU
CI hit ERR=1.8e-3 (> 5e-4 tolerance) for a scalar-output f32 dot product
(m=1,n=1,k=2048); didn't reproduce locally in 8 tries, so likely an
internal fp16 accumulation path the GPU plugin picks for this tiny
shape. m=1 output dim doesn't occur in real model weights, so gate it.
* ggml-openvino: make SoftPlus decomposition opt-in native
Assisted-by: Codex
---------
Co-authored-by: Mostafa Faheem <mostafaaafaheem@gmail.com>
Co-authored-by: Mustafa Cavus <mustafa.cavus@intel.com>
Co-authored-by: zhaixuejun1993 <xuejun.zhai@intel.com>
Co-authored-by: ravi9 <ravi.panchumarthy@intel.com>
* metal : add FA kernels for HSK=96, HSV=64 (MiniCPM3)
MiniCPM3 sets attention.key_length to 96 and does not set
attention.value_length, which defaults to n_embd / n_head = 64. Metal had no
(96, 64) instantiation, so -fa auto aborted on the missing
kernel_flash_attn_ext_vec_f16_dk96_dv64.
Instantiate the tile kernel at (96, 64) for every K/V type that already has
(96, 96), and the vec kernel for the NE=4 configurations. Of the NE values the
vec dispatch considers, only NE=4 works here, because NL = 32/NE has to divide
both DK/4 = 24 and DV/4 = 16.
* tests : avoid redundant FA vec slice coverage
* sycl: GPU-resident TOP_K for large k, parallelised over the device
The SYCL backend refused GGML_OP_TOP_K above k = 32 and let it fall back to
the CPU, a backend round-trip per call. The limit was not conservatism: the
scan-merge kernels keep (split_block + 1) * k candidate (value, index) pairs
in SLM, so at k = 128 a work-group already needs 132 KB and cannot launch.
qwen4exp's sparse-attention indexer asks for k = 2048 in 12 layers on every
token, so this fired at every context length.
Add a radix select for large k. The k-th largest is found by four
most-significant-first passes over an order-preserving unsigned key: histogram
the digit over the candidate set, walk the buckets from the top, and recurse
into the one where the running count reaches what is still needed. SLM holds
the histogram rather than candidates, so the footprint is independent of k.
A final pass emits every column beating the pivot plus exactly as many
pivot-equal columns as are still missing, so duplicate keys still yield
exactly k distinct indices. Output order is not required and is not paid for:
ggml-cpu/ops.cpp swaps its first two outputs to say so.
The key folds -0.0 onto +0.0 so its equivalence classes match the reference
comparator, under which the two tie. NaN has no defined order in the reference
(its comparator is not a strict weak order there); here +NaN keys above +inf
and -NaN below -inf, which at least makes the result deterministic.
One work-group per row leaves the device idle whenever a graph has fewer rows
than it has cores, which at batch size 1 means one work-group full stop:
qwen4exp tops-k a tensor of shape [n_kv, n_tokens/n_stream, n_stream], so
token generation gives nrows == 1, and the backend sampler reshapes logits to
a single row as well. Measured, ne=[200000,1] and ne=[200000,16] cost 358.0 us
and 363.4 us -- sixteen rows for 1.5% more wall-clock.
So also spread a row over several groups when there are too few rows to cover
the device. Per-pass state moves to global memory and each digit pass becomes
its own launch, since a work-group barrier can no longer span the row. Groups
accumulate in SLM and contribute 256 global atomics each, keeping global
traffic per-group rather than per-element, and the last group of a row -- the
one whose fetch_add returns G-1 -- performs that pass's scan, holding the
launch count at one per digit plus one emit. The group count comes from the
device and is floor-divided by nrows, so a row count that already covers the
device is left whole and pays nothing. Below 64K columns the single-group
kernel finishes inside the cost of the extra launches and stays in charge.
Reading the row's prefix/mask/need through a device-scope atomic_ref costs
more than the sweep it guards: those loads are uncached, so passes 2-4 ran at
49 us against 12 us for pass 1. One lane reads them into SLM and the group
takes them from there -- 208 us -> 44.6 us at ne=[131072,1], k=2048.
The block size now takes the device's max_work_group_size instead of a cap of
512. The cap was never a floor, so a device reporting 512 is unaffected; one
allowing 1024 was being given half its width.
Finally, put the scan-merge gate where the two paths actually cross. That
kernel's cost climbs with k while the radix select's does not; measured over
widths from 2 to 200K columns and row counts from 1 to 8192, radix is ahead
everywhere from k = 8 up and behind at k <= 2, where scan-merge's smaller
fixed cost wins. The short-row corner (ncols=2, nrows=65536, as in bailingmoe2
group selection) is exactly where radix loses at low k, and the gate keeps it
on scan-merge.
Op-level against the CPU-fallback path this replaces, and against the
single-group radix select for the split: 4.98x at ne=[131072,1] k=2048,
6.65x at ne=[151936,1] k=40, 13.35x at k=20, 118x at ne=[65000,16] k=32.
No measured shape regressed. End to end on 3x Arc Pro B60 with
Qwen3.8-Flash-Next UD-IQ4_XS, llama-bench tg64, the parallelisation is worth
5.91 -> 6.05 t/s at d=131072 and a wash at shallower depths. Perplexity over
wikitext-2 is unchanged within noise at both 512 and 81920 context.
test-backend-ops: 525/525 TOP_K (previously every k > 32 case was refused),
880/880 MUL_MAT_ID. Perf coverage added for k > 32 at large widths and for the
short-row corner, neither of which was exercised before.
* move topk-select to topk-radix.{cpp|hpp}
---------
Co-authored-by: cwriter <cwriter@localhost>
Disable the ggml-cpu precompiled header and remove the
std::hardware_destructive_interference_size branch from CACHE_LINE_SIZE.
The PCH force-includes ggml-impl.h before ops.h, which pulls in <new>
via <array>/<vector> and defines __cpp_lib_hardware_interference_size.
This makes the C++ kernels use CACHE_LINE_SIZE = 256 (hardware
destructive interference size) while the C work-buffer sizing code in
ggml-cpu.c always uses the fallback 64. The mismatch undersizes the
rope work buffer by (CACHE_LINE_SIZE/4 - 16) * n_threads * 4 bytes,
causing a heap-buffer-overflow that corrupts the heap and later crashes
in ggml_compute_forward_rope_flt.
Disabling the ggml-cpu PCH restores the natural include order so
ops.h is processed before <new>, keeping CACHE_LINE_SIZE consistent.
Removing the std::hardware_destructive_interference_size branch makes
the value deterministic and include-order independent.
ref: https://github.com/ggml-org/llama.cpp/issues/28858
Assisted-by: pi:llama.cpp/DeepSeek-V4-Flash-Vision-Exp
* ggml-cuda: fallback to F32 on device without BF16 hardware acceleration: (Nvidia >= AMPERE, AMD >= RDNA3 or = CDNA)
* apply logic to NVIDIA as well
---------
Co-authored-by: Johannes Gäßler <johannesg@5d6.de>
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