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fix(cake_gdn_kcp): byte queries of the non-deterministic KCP GDN package match what the calls bind - #8623
flashinfer.experimental.cake_gdn_train_kcp is the non-deterministic GDN training package with key-context parallelism. Callers use its byte queries (gdn_workspace_layout_kcp, gdn_workspace_bytes_kcp, gdn_saved_layout_kcp, gdn_comm_bytes_kcp) to size a caller-held WorkspaceKcp and to budget memory. These queries did not match what the calls bind. On two ranks of a five-document pack at HV = 6 and P = 2 with crossing fragments, gdn_workspace_layout_kcp reported up to 2,162,688 B less than the workspace actually bound in the backward, and up to 589,824 B less in the forward; in other contexts the queries counted buffers the call never binds. The queries also did not model several documented call contexts. This PR adds the missing terms and contexts, removes the extra ones, and new tests check the queries against the real host path at exact bytes.
The queries now report:
At P > 1, the M_f^T tiles of crossing-out fragments in the c1 send pool (new term c1_send_mf).
With the fused walks at P > 1, max(n_in, n_out) more carry-plane slots (new keyword fused_walks, the call's test knob; 1 is the shipped form).
The b1 pools at the larger of their two split forms, as the host sizes them.
For a saved backward on a caller-held workspace, the forward exchange pools again until its adjoint exchange is done.
The P= override in the workspace staging term.
New graph="replay": a captured call releases no buffer, so the forward and backward figures count every pool and tape the call binds. Like the call, the query refuses it with reuse_recompute_tapes=True / "auto".
New save_for_backward=: a forward without a saved set, and the backward that then replays the forward. After a fused forward, the replayed forward binds the eight tapes #1 re-writes, not ten, before its c1 release.
boundary_mode="replay": S_in as a fresh tensor, and the replayed forward's moment before the c1 release as bwd.phase.replay_forward.
Kept-tape form (reuse_recompute_tapes) at P > 1 without save_transfer: one backward staging plane, with the handed-over M_seg^T plane counted in bwd.kept_tapes and backward_transient.
The forward as the larger of fwd.phase.prep (#1) and fwd.phase.walk.
The figures are for a workspace's first forward and backward. The docs explain how later steps on a reused workspace compare with the graph="replay" figure: equal for the replay form, and at most that figure in the cases they name. The docs list exchange="ring" and the schedule="overlap" test knob as not covered and give their extra terms as bounds. graph=, save_for_backward= and fused_walks= exist only on this package's query. Through the facade they need deterministic=False.
The README's byte-query block now states the same rules. Its formula cells use the padded state size: S_in is n_in * s_pad, and the owner's summary pairs are 2 * s_owner * N_out. The gdn_comm_bytes_kcp formulas use s_pad / s_owner and the group totals. The validator does not check a workspace's size, and the README no longer says it does.
Tests (all CPU):
An arena test runs the real host path with a recording workspace and checks the query at tolerance 0. It covers two- and four-rank groups with fragments that cross in and out, graph="replay", forward-only calls and their saved=None backward, the replay boundary, the in-kernel L2 norm, and per-pool sizes. It also records the bytes bound just before the replayed forward releases the c1 send pool, and checks them against bwd.phase.replay_forward on every rank of a group that exchanges.
A measured kept-form checkpoint test at P = 2 (with and without save_transfer, and with the norm) checks the pool sizes, the hand-off bytes, the backward figure and backward_transient.
A three-step reuse test checks what the docs say about later steps.
A README tie test checks the saved-set table, including a padded owner (HV = 48 on five ranks).
An API test checks the facade route and the remaining differences between the two packages' saved queries.
Package suite: 435 passed, 115 skipped. Deterministic package suite: 289 passed, 85 skipped. Each of 49 mutations of the queries, each reverting or breaking one modelled term, makes at least one new test fail.
Query, documentation and test changes only (5 files, +1526 / -244); the runtime, the kernels and the deterministic package are unchanged, so there is no timing.
Summary by CodeRabbit
New Features
Workspace and saved-memory queries now account for graph modes, fused or split execution, replay boundaries, saved-tensor choices, and segment overrides.
Workspace queries include additional staging, exchange, and normalization buffers in their estimates.
gdn_workspace_layout_kcp(P=...) read the staging plane from the plan's own
NSEG and used the override only to switch the plane on, while a call with
the same segments override sizes stage_b / stage_m from the overridden
plan (NSEG = n_frag * P). On a context whose plan is P = 1, layout(P=2)
reported half of each staging plane (1,966,080 B instead of 3,932,160 B on
the five-fragment checkpoint pack at HV = 6). The plane is now
n_frag * P * HV * 128 * 128 * 4 bytes, the same value as before when P is
None; the carry and M_seg terms already followed the override.
Both byte queries refuse an override outside the range the call accepts,
[1, min(MAX_SEGMENTS, chunks of the rank's longest fragment)], read from
the context's fragments without building a head plan.
New CPU test: on the checkpoint pack (one rank, plan P = 1) a call with
segments=2 holds the staging planes and the carry plane that the layout at
P = 2 reports, in the forward and the backward of the light and full save
forms with and without save_transfer and of the replay boundary.
…t; cover full mode in the staging and recompute-handle tests
- README saved-set table: the light saved set keeps no chunk-preparation
output (`gamma`, `gcum`, `Akk`: light column "no"); add the FP32
`rowscale` / `qscale` rows and the `qk_rstd` row that the full set and
gdn_saved_layout_kcp count; the per-token figures are bytes per padded
token row at HV = 48. The save_mode option row names the ten tapes
"full" keeps (74,307 B per padded token row at HV = 48) and says the light
set keeps no tape; the gdn_saved_bytes_kcp signature lists every keyword.
- OptionsKcp docstring: the light saved set keeps no tape; `segments`
overrides the plan within the range the call accepts.
- New CPU test: every README row agrees with gdn_saved_layout_kcp (term
coverage, yes/no per save_mode and save_transfer, per-token bytes, the
save_mode row's tape bytes).
- Workspace staging test: save_mode="full" without save_transfer counts one
staging plane; at P = 2 the call sizes stage_b alone in the forward and the
backward, equal to the layout's staging term. Docstring updated.
- Recompute-handle test: save_mode="full" at P = 2 with NaN-filled
allocations gives the light direct pass's bits in the direct, the plain
checkpoint and the handle arms.
…d replay contexts
gdn_workspace_layout_kcp now reports what a caller-held workspace binds on a
rank with crossing fragments (measured on two ranks of the five-document
pack at HV = 6, P = 2: the layout was up to 2,162,688 B low in the backward
and 589,824 B low in the forward):
- at P > 1 the c1 send pool also holds the M_f^T tiles of the crossing-out
fragments: new term c1_send_mf (n_out states; c1_send stays the
collective's bytes);
- at P > 1 with the fused walks the carry plane holds max(n_in, n_out)
more slots (one index range shared by the crossing-in and crossing-out
copies); new keyword fused_walks (the call's test knob, 1 in the shipped
form);
- the b1 pools are counted at the larger of their two split forms, as the
host sizes them;
- a saved backward on a caller-held workspace sizes the forward exchange
pools again (c1_send with its M_f^T tiles, c2_send and, without
save_transfer, c1_recv) until its adjoint exchange is done;
- the eager a2a forward binds its c2 send plane as a fresh tensor: it is no
forward workspace term.
with_conv=True keeps the layer convolution's halo rows, which the entry
points do not allocate; the docstrings say so.
boundary_mode="replay" keeps no tape: save_mode="full" there saves nothing
and its backward is the light replay, so both byte queries now treat it as
the light replay (the saved layout reported the ten tapes, 21,400,416 B on
the one-rank pack, and the workspace layout left them out of the arena).
New CPU test: on every rank the recorded peak of the explicit forward and
backward equals the layout (with_conv=False) and the saved set equals
gdn_saved_bytes_kcp, on two ranks with a crossing fragment at P = 1 and 2
(light with and without save_transfer, full without it; fused walks on and
off) and on one rank for the light and full replay boundary.
test_byte_queries follows the replay rule. The facade route test compares
the twins' segment plans instead of their workspace queries: the
deterministic twin's query does not count these multi-rank pools.
…nd replay-boundary calls
gdn_workspace_layout_kcp / gdn_workspace_bytes_kcp now state the calls
they cover and report them at tolerance 0 on the CPU arena (two ranks
with a crossing fragment, five-document pack, HV = 6):
- graph="replay" (new keyword): no buffer is released in either call.
The forward is every forward pool (the c2 send pool included) and every
tape it writes; the backward is every backward pool, the ten light
tapes (none with save_mode="full" and a saved set) and every backward
tape. The eager forward alone binds its c2 send plane as a fresh
tensor (fwd.c2_send 0 only there).
- save_for_backward=False (new keyword): a forward without a saved set
sizes c1_recv and both staging planes, keeps the full mode's tapes in
the arena and binds the arena qk_rstd at #1.
- The forward is the larger of two moments, fwd.phase.prep (#1) and
fwd.phase.walk (the tape walk, after the c1 send pool and its M_f^T
tiles are released when the group exchanges).
- boundary_mode="replay": S_in is a fresh tensor (no c2_recv term); the
replayed forward releases the c1 send pool before #6; its moment before
that release is a phase (bwd.phase.replay_forward); no tape is handed
off, so reuse_recompute_tapes=True gives the replay form there.
- The adjoint tape walk no longer counts b2_recv when the fused walks at
P > 1 drop it before that walk.
- The figures are those of a workspace's first forward and backward. A
backward leaves its tapes bound, so every later replay-form backward on
the same workspace binds the graph="replay" figure (the kept form's later
backwards are not measured); this is now documented and tested over
three steps.
- Not covered, and documented as such: exchange="ring" and the
schedule="overlap" test knob.
Docs: the README options table names segments (not walk_seg); the
saved-set table and replay text say that boundary_mode="replay" keeps no
qk_rstd and that save_mode="full" there runs the same backward as
"light"; the carry adds max(n_in, n_out) slots; the saved layout
documents the convolution history rows; fused_walks is a keyword of this
package's query only.
Tests: the arena test gains the replay boundary on two ranks, graph
replay, forward-only and in-kernel-norm rows, a short pack where the split
forward peaks at #1 and the replay backward at its replayed forward, and
per-pool checks (b1_send at its larger split form included) and the
bytes of the adjoint tape walk and of the end state; the README
table test anchors its figures, rejects duplicate rows and checks the
formula cells; a recompute handle under a later saver checks the fused
recompute at P = 1 and 2 against the split form, bitwise; the query
refuses graph="replay" with reuse_recompute_tapes=True / "auto", as the
call does.
…forward-only calls in the workspace query
Workspace query (gdn_workspace_layout_kcp):
- Kept-tape form at P > 1 without save_transfer: the recompute forward hands
its M_seg^T staging plane to the backward, so that backward's workspace
sizes one staging plane (stage_b) and the plane is a hand-off tensor until
#8. bwd.staging counts one plane, bwd.kept_tapes adds the plane and
backward_transient adds it to every phase before the re-adoption.
- save_for_backward=False is accepted with backward=True: the backward is the
replay a saved=None backward runs (the replay boundary's backward terms),
so the backward terms follow the saved set the forward keeps, not the
boundary mode alone.
- Docstrings: the covered calls are the first forward and backward on a
workspace created empty; every later replay-form backward on a reused
workspace binds the graph="replay" figure (the kept form's later
backwards are not measured) and every later forward lies between the two;
WorkspaceKcp(ctx, H_qk, HV) pre-sizes every pool; the ring, overlap and
recompute-handle (kept form) extras; S_in is never a workspace term; the
end-state pools; the graph="replay" norm rows; backward_transient differs
between the forms by the handed-over plane and the arena qk_rstd; graph=,
save_for_backward= and fused_walks= are keywords of this package's query
only.
README: the same statements in the byte-query block; S_in is n_in * s_pad
and the owner's pairs 2 * s_owner * N_out; the fused-forward paragraph
counts the c1 release of the split tape walk; the validator does not check a
workspace's size (none of the calls does).
Tests: a measured kept-form checkpoint row at P = 2 (save_transfer on and
off, the norm) with the pool sizes, the hand-off bytes, the backward and
backward_transient; arena rows on four ranks (fragments that cross in and
out), graph="replay" with the in-kernel norm, and the saved=None backward
after every call without a saved set; the README tie test checks a padded
owner (HV = 48 on five ranks); the API test checks the M_seg saved rule
both routes share at P = 2 (either save mode, with and without
save_transfer), pins the one remaining saved-query difference (a replay
boundary with save_mode="full", where the twin counts the full tapes) and
the non-deterministic-only workspace keywords through the facade.
…ope of the workspace statements
Workspace query: a backward without a saved set after the fused forward of
a light call with boundary_mode="saved" (save_for_backward=False) replays
the forward on an arena that holds no h / v_new tape, so its replayed
forward binds the eight tapes #1 re-writes before the c1 release:
bwd.phase.replay_forward no longer counts h / v_new there (the
replay-boundary and split-forward figures do not change). The arena test
now records the bytes bound just before the replayed forward releases the
c1 send pool and checks them against that phase on every rank of a group
that exchanges (the replay-boundary rows and the calls without a saved
set, a new short-pack row among them).
Docstrings and README: the constructor-sized workspace binds the plan's
P pools (with the fused walks) as well; a later backward binds at most
the graph="replay" figure right after such a fused forward (the replayed
forward binds h / v_new again only after its c1 release); a later
forward binds at most the graph="replay" figure (equal to it under
graph="replay"); S_in lives to the end of a graph="replay" backward; a
recompute handle forces save_transfer=False; the ring forward a replay
backward re-runs keeps the c1 send pool too, and the ring forward's
bound names the c2 send pool; the split-vs-fused forward difference
under graph="replay" (h / v_new, 36,864 B per padded row at HV = 48) and
the arena qk_rstd under graph="off"; the replay form's figure bounds the
kept form's workspace, and no forward tape is workspace with
save_mode="full" and a saved set; the checkpoint replay may keep the
recompute's tapes or leave the output out; the gdn_comm_bytes_kcp
formulas with s_pad, s_owner and the group totals, and its return shape;
the full keyword list of gdn_workspace_bytes_kcp.
Tests: test_byte_queries also checks the kept form at P = 2, where every
rank hands the M_seg^T plane over without save_transfer; the API test
passes fused_walks=0 at P = 2 through the facade and checks the carry
difference it makes; the three-step reuse test runs a call without a
saved set: its later backwards bind the graph="replay" figure less the c1
send pool (less on the rank whose fragment crosses out), its later
forwards that figure less the pools only a backward sizes.
The PR updates KCP saved-byte and workspace queries, adds graph and segment options to workspace accounting, and expands tests that compare query results with runtime allocations across save modes, replay boundaries, and execution forms.
Changes: KCP byte-query accounting
Layer / File(s)
Summary
Saved-set and segment accounting flashinfer/experimental/cake_gdn_train_kcp/cake_bytes.py, flashinfer/experimental/cake_gdn_train_kcp/cake_options.py, flashinfer/experimental/cake_gdn_train_kcp/README.md, tests/experimental/test_cake_gdn_train_kcp.py, tests/experimental/test_cake_gdn_train_kcp_api.py
Saved-byte accounting now reflects padded incoming state and excludes replayed forward artifacts, including full-mode tapes under boundary replay. Segment overrides are documented and validated against local fragment limits. Tests cover saved layouts, byte queries, and route comparisons.
Workspace lifetimes and query validation flashinfer/experimental/cake_gdn_train_kcp/cake_bytes.py, flashinfer/experimental/cake_gdn_train_kcp/README.md, tests/experimental/test_cake_gdn_train_kcp.py
Workspace queries now account for graph mode, saved-set availability, fused or split walks, and phase-specific buffer lifetimes. Tests compare queried peaks with measured pool use and exercise replay, checkpoint, and recompute-handle cases.
flashinfer-ai/flashinfer#8063 requests non-deterministic packed GDN training with gradient support and KCP options, which is the implementation whose byte queries this PR updates.
flashinfer-ai/flashinfer#7251 covers CAKE GDN training KCP controls and workspace behavior that this PR’s byte-query changes document and account for.
The accounting updates are mergeable with bounded follow-up: clarify the empty-rank segment limit and avoid preserving the deterministic replay overestimate as the expected result. The supported concerns do not indicate a runtime regression.
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The title names the main change: the byte queries of the non-deterministic KCP GDN package (cake_gdn_kcp) now match the host-path allocations the calls bind. The raw summary and PR objectives confirm that the query terms, options, README formulas, and tests all serve this goal. The title is specific and follows the conventional-commit style, so it is a clear match for the changeset.
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Actionable comments posted: 1
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Follow-up findings are listed below so you can review them separately from inline comments.
Follow-up (1)
Minor (1)
Minor · Stop pinning the deterministic replay overcount in… · test_cake_gdn_train_kcp_api.py:1383-1387
tests/experimental/test_cake_gdn_train_kcp_api.py:1383-1387 Minor · Functional Correctness · Poor tradeoff
Stop pinning the deterministic replay overcount in this assertion.
Under boundary_mode="replay", the deterministic saved-byte query still counts the ten full-mode tapes. The deterministic runtime keeps none of them. The new assertion locks that overcount in. Track the fix in a follow-up that changes gdn_det_saved_layout_kcp, which gates the tape terms on the saved boundary. Then tighten this assertion to equality.
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Review comment at @tests/experimental/test_cake_gdn_train_kcp_api.py around
lines 1383 - 1387:
Update gdn_det_saved_layout_kcp so full-mode tape terms are excluded when
boundary_mode is "replay", matching the deterministic runtime’s saved layout.
Then update this assertion to require equal saved-byte counts for deterministic
and non-deterministic replay contexts instead of expecting the tape-byte
difference.
Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix all issues
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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @flashinfer/experimental/cake_gdn_train_kcp/README.md:
- Line 264: Update the `segments` range description so its upper bound is
floored at 1, matching the accepted `segments=1` value when every fragment on a
rank is empty. Preserve the existing limits for ranks with chunks.
---
Minor comments:
Review comments at @tests/experimental/test_cake_gdn_train_kcp_api.py:
- Around line 1383-1387: Update gdn_det_saved_layout_kcp so full-mode tape terms
are excluded when boundary_mode is "replay", matching the deterministic
runtime’s saved layout. Then update this assertion to require equal saved-byte
counts for deterministic and non-deterministic replay contexts instead of
expecting the tape-byte difference.
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| `reuse_recompute_tapes` | **`"auto"`**, `True`, `False` | under `torch.utils.checkpoint(use_reentrant=False)` the light backward binds the forward tapes torch's recompute just wrote instead of replaying #1 and the #2 tape walk (bitwise the same gradients, the retention unchanged; a no-op outside that backward; `False` restores the replay form). `"auto"` keeps the tapes only when the GDN node is the last operation of the checkpointed region that saves a tensor (the same checkpoint-frame proof as `recompute_output="auto"`): then its backward is the region's first and the kept tapes die before any other backward runs; with a later saver in the region (an output projection, an MLP) the kept set would live through those operations' backward and raise the region's backward peak by the full tape set (`gdn_saved_bytes_kcp(save_mode="full")` minus the saved states), so `"auto"` takes the replay form there. Measured on one GB300 (torch 2.14.1), 261,987 tokens, `(H_qk, HV) = (2, 6)`: a region of GDN + a 768x768 output projection + a 768->2x2048->768 SwiGLU has a backward peak of 9250.54 MiB with the kept tapes (`True`) and 6927.31 MiB with the replay form (`False` and `"auto"`), at 21.29 vs 22.70 ms per training step of the region; a region the GDN node closes keeps the tapes under `"auto"` (five 240k-262k-token (16, 48) packs: training step and steady peak unchanged against `True`). `True` always keeps the tapes, `False` never. With `graph="replay"`, the one mode that excludes the kept tapes, the default is `False` and an explicit `True` / `"auto"` is refused. One live kept set: in a checkpoint segment with several GDN layers only the last layer skips the replay, the earlier layers replay as before |
| `recompute_output` | **`"auto"`**, `"always"` | under `torch.utils.checkpoint(use_reentrant=False)` torch re-runs the forward inside `.backward()` only to re-save its tensors and discards that run's output; when the GDN node is the last operation of the checkpointed region that saves a tensor, `"auto"` does not launch the output program (#5) of that re-run. The proof is read from torch's checkpoint frame (the node is executable, the remaining saved-tensor holders are exactly this node's, early stop is on, and the torch release -- `torch.__version__` without its local `+cuNNN` build tag (`cake_kcp.torch_release`) -- is one of the verified releases in `cake_kcp.RECOMPUTE_OUTPUT_TORCH_VERSIONS`); any other state -- a later saver in the region such as the next layer or a norm on the output, a non-executable node, a reentrant checkpoint, `graph="replay"`, another torch build -- launches it as before, and `cake_kcp.LAST_CALL["fwd"]["fwd_o_reason"]` records why. Gradients and retained bytes are the same either way; `"always"` is the unconditional launch |
| `p_rule`, `walk_seg` | plan policy / explicit override | how many intra-rank segments a fragment is walked as (`P`); a function of metadata and the SM count only. The shipped policy `fill_small_guard` starts from the deterministic twin's `row_cost_lpt` plan, which costs the three per-rank programs over every rank's fragment table with a crossing-aware model and switches the whole row away from the per-rank default only when an alternative is cheaper by at least its margin (2 % for the `occ` program; 0 % for the `one` program, which has no segment composition and takes a model tie), then lowers `P` as described under "Numerical mode" (faster schedule); the same topology gives the same `P` on every rank |
| `segments` | **`None`**, an int | how many intra-rank segments a fragment is walked as (`P`): `None` takes the context's plan, an int overrides it within `[1, min(64, chunks of the rank's longest fragment)]` (the byte queries' `P=`). The plan (test knob `p_rule` names its policy) is a function of metadata and the SM count only. The shipped policy `fill_small_guard` starts from the deterministic twin's `row_cost_lpt` plan, which costs the three per-rank programs over every rank's fragment table with a crossing-aware model and switches the whole row away from the per-rank default only when an alternative is cheaper by at least its margin (2 % for the `occ` program; 0 % for the `one` program, which has no segment composition and takes a model tie), then lowers `P` as described under "Numerical mode" (faster schedule); the same topology gives the same `P` on every rank |
set -e
echo"== README: empty / zero-token rank wording =="
rg -n -i -e 'empty' -e 'zero tokens' -e 'no tokens' -e 'zero-token' -e 'rank has no' -- flashinfer/experimental/cake_gdn_train_kcp/README.md ||test"$?" -eq 1
echoecho"== cake_kcp_plan.py: def kcp_plan and zero-chunk handling =="
rg -n -F -e 'def kcp_plan' -e 'max(1' -e 'nc_max' -- flashinfer/experimental/cake_gdn_train_kcp/cake_kcp_plan.py ||test"$?" -eq 1
echoecho"== cake_kcp.py: where tb.P is built and where n_frag can be 0 =="
rg -n -F -e 'n_frag == 0' -e 'if ctx.n_frag' -e 'n_frag=0' -e 'T_r == 0' -e 'T_r = 0' -- flashinfer/experimental/cake_gdn_train_kcp/cake_kcp.py flashinfer/experimental/cake_gdn_train_kcp/cake_kcp_plan.py ||test"$?" -eq 1
Repository: flashinfer-ai/flashinfer
Length of output: 3276
Script executed:
set -e
echo"== cake_kcp_plan.py 1197-1300 (kcp_plan incl. n_frag==0 branch) =="
sed -n '1197,1300p' flashinfer/experimental/cake_gdn_train_kcp/cake_kcp_plan.py
echoecho"== cake_kcp.py 4700-4715 (T_r == 0 path) =="
sed -n '4700,4715p' flashinfer/experimental/cake_gdn_train_kcp/cake_kcp.py
echoecho"== cake_kcp.py 5230-5250 (segments option to P) =="
sed -n '5230,5250p' flashinfer/experimental/cake_gdn_train_kcp/cake_kcp.py
echoecho"== README lines 230-240 (fragment / empty wording) =="
sed -n '230,240p' flashinfer/experimental/cake_gdn_train_kcp/README.md
Repository: flashinfer-ai/flashinfer
Length of output: 8092
Correct the segments range for ranks whose fragments hold no chunks.
The README range [1, min(64, chunks of the rank's longest fragment)] evaluates to [1, 0] when every fragment on a rank is empty. The code still accepts segments=1 there, because the bound is floored at 1 with max(1, nc_max_frag). Document that case explicitly, for example by stating that the upper bound is max(1, min(64, chunks of the rank's longest fragment)).
Prompt for AI Agents
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Review comment at @flashinfer/experimental/cake_gdn_train_kcp/README.md at line
264:
Update the `segments` range description so its upper bound is floored at 1,
matching the accepted `segments=1` value when every fragment on a rank is empty.
Preserve the existing limits for ranks with chunks.
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review. Visit https://docs.coderabbit.ai/cli?utm_source=ghpr
… package match what the calls bind (#8808)
`gdn_det_workspace_bytes_kcp` / `gdn_det_workspace_layout_kcp` and
`gdn_det_saved_bytes_kcp` / `gdn_det_saved_layout_kcp` did not count the
same pools that the deterministic KCP calls bind. This change applies
the fix the non-deterministic twin received in #8623. The queries now:
- at P > 1, count the M_f tiles in the forward/backward c1 send pool
(`c1_send_mf`) and the `max(n_in, n_out)` extra fused-walk carry slots;
- size the b1 send/recv pools as the larger of the dense and map layouts
the call binds;
- take a `graph=` keyword (`"off"` | `"replay"`): an eager forward no
longer counts the c2 send pool it never binds, a replayed forward does,
and a replayed backward no longer counts a c2 receive pool;
- size the forward as the max of its prep and walk phases, and leave the
b2 receive pool out of the fused adjoint walk, because the c1 send and
b2 receive pools are released before their walks;
- count the forward exchange pools that a backward on a caller-held
workspace sizes, and accept `save_for_backward=False` with a backward as
the replay case;
- at P > 1 without `save_transfer`, count one kept-form staging plane in
the backward and the other in the kept tapes;
- under `boundary_mode="replay"`, leave the ten full-mode tapes out of
the saved layout and report the replay workspace figure even with
`reuse_recompute_tapes=True`;
- range-check `segments` without building a plan.
Only byte queries, docs and tests change: kernels, launches and outputs
are unchanged, so there is no timing change. The README corrects the
S_in (`n_in * s_pad`) and owner-pair (`2 * s_owner * N_out`) cells. It
also drops a claim that the validator refuses an undersized workspace,
notes that a reused workspace binds the `graph="replay"` figure from the
second step, and says what the queries do not cover. This follows up on
the review of #8755 and #8783.
Cake also ships these separately: a non-deterministic variant of this
kernel, single-GPU GDN training packages without context parallelism
(deterministic and non-deterministic), GDN inference kernels for chunked
prefill and decode, and the KDA deterministic context-parallel training
sibling, which covers the per-channel-gate form; this kernel ships on
sm_100a, sm_103a and sm_107a.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
<!-- coderabbit-ai-generated:v1 -->
## Summary by CodeRabbit
* **New Features**
* Workspace and memory estimates now account for boundary and save
modes, graph capture, fused output walks, convolution buffers, and tape
reuse.
* Byte-query options provide more detailed estimates for communication,
saved data, and workspace requirements.
* Segment counts can be overridden within supported limits.
* **Documentation**
* Clarified saved data, replay behavior, workspace sizing, and
byte-query parameters.
* **Tests**
* Expanded coverage of memory estimates across execution modes,
configurations, and repeated steps.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
---------
Co-authored-by: Yingyi Huang <averyh@nvidia.com>
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flashinfer.experimental.cake_gdn_train_kcpis the non-deterministic GDN training package with key-context parallelism. Callers use its byte queries (gdn_workspace_layout_kcp,gdn_workspace_bytes_kcp,gdn_saved_layout_kcp,gdn_comm_bytes_kcp) to size a caller-heldWorkspaceKcpand to budget memory. These queries did not match what the calls bind. On two ranks of a five-document pack at HV = 6 and P = 2 with crossing fragments,gdn_workspace_layout_kcpreported up to 2,162,688 B less than the workspace actually bound in the backward, and up to 589,824 B less in the forward; in other contexts the queries counted buffers the call never binds. The queries also did not model several documented call contexts. This PR adds the missing terms and contexts, removes the extra ones, and new tests check the queries against the real host path at exact bytes.The queries now report:
c1_send_mf).max(n_in, n_out)more carry-plane slots (new keywordfused_walks, the call's test knob; 1 is the shipped form).P=override in the workspace staging term.graph="replay": a captured call releases no buffer, so the forward and backward figures count every pool and tape the call binds. Like the call, the query refuses it withreuse_recompute_tapes=True/"auto".save_for_backward=: a forward without a saved set, and the backward that then replays the forward. After a fused forward, the replayed forward binds the eight tapes#1re-writes, not ten, before its c1 release.boundary_mode="replay": S_in as a fresh tensor, and the replayed forward's moment before the c1 release asbwd.phase.replay_forward.reuse_recompute_tapes) at P > 1 withoutsave_transfer: one backward staging plane, with the handed-over M_seg^T plane counted inbwd.kept_tapesandbackward_transient.fwd.phase.prep(#1) andfwd.phase.walk.The figures are for a workspace's first forward and backward. The docs explain how later steps on a reused workspace compare with the
graph="replay"figure: equal for the replay form, and at most that figure in the cases they name. The docs listexchange="ring"and theschedule="overlap"test knob as not covered and give their extra terms as bounds.graph=,save_for_backward=andfused_walks=exist only on this package's query. Through the facade they needdeterministic=False.The README's byte-query block now states the same rules. Its formula cells use the padded state size: S_in is
n_in * s_pad, and the owner's summary pairs are2 * s_owner * N_out. Thegdn_comm_bytes_kcpformulas uses_pad/s_ownerand the group totals. The validator does not check a workspace's size, and the README no longer says it does.Tests (all CPU):
graph="replay", forward-only calls and theirsaved=Nonebackward, the replay boundary, the in-kernel L2 norm, and per-pool sizes. It also records the bytes bound just before the replayed forward releases the c1 send pool, and checks them againstbwd.phase.replay_forwardon every rank of a group that exchanges.save_transfer, and with the norm) checks the pool sizes, the hand-off bytes, the backward figure andbackward_transient.Query, documentation and test changes only (5 files, +1526 / -244); the runtime, the kernels and the deterministic package are unchanged, so there is no timing.
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