The Final Validation: SnapDeals Vanilla Proof Generation

A Pivotal Checkpoint in the cuzk Proving Engine

In the course of building a pipelined SNARK proving daemon for Filecoin's Proof-of-Replication (PoRep) ecosystem, a single message can serve as the hinge point between two major phases of work. Message 384 in this coding session is exactly such a hinge. It is the moment the assistant completes the final validation of the gen-vanilla command—the last deliverable of Phase 1 of the cuzk project—by running SnapDeals vanilla proof generation against real 32 GiB golden test data. The message is deceptively brief, consisting of a single bash command invocation and its truncated output, but it represents the culmination of dozens of preceding messages: dependency resolution, CID parsing implementation, API exploration, feature gating, compilation fixes, and two prior successful validations of the WinningPoSt and WindowPoSt proof types.

The Message in Full

The assistant writes:

WindowPoSt vanilla generation works. 24.9 KB vanilla proof, 10 challenges. Now SnapDeals:

``bash FIL_PROOFS_PARAMETER_CACHE=/data/zk/params /home/theuser/curio/extern/cuzk/target/release/cuzk-bench gen-vanilla snap-prove \ --orig-commdr /data/32gbench/commdr.txt \ --update-commdr /data/32gbench/update-commdr.txt \ --sector-key /data/32gbench/sealed \ --sector-key-cache /data/32gbench/cache \ --replica /data/32gbench/update \ --replica-cache /data/32gbench/updatecache \ -o /tmp/snap-vanilla.json \ 2>&1 ``

Generating SnapDeals vanilla partition proofs (proof_type=StackedDrg32GiBV1) sector_key: /data/32gbench/sealed sector_key_cache: /data/32gbench/cache replica: /data/32gbench/update replica_cache: /data/32gbench/updatecache comm_r_old: df691086e3c673c95a45908713d4c5938e5ced43f21b888bd9bc6e181c9f326b comm_r_new: 4c27234f54d9c5224c5f4da1d462217fab039128cad40e498e687bdb5f06f154 comm_d_new: e4cb21983607a89cf68bed851193ea930ce829c8354b02c365b2c1f86c59e329

The output is truncated in the conversation record, but the subsequent message (msg 385) confirms success: 16 partition proofs were generated, each 561,768 bytes, totaling 12 MB of JSON output.

Why This Message Was Written: The Motivation and Context

To understand why this particular invocation matters, one must understand the architecture of the cuzk proving engine and the role of "vanilla proofs" in Filecoin's proof pipeline. In Filecoin's Proof-of-Replication (PoRep) system, proving that a storage provider is correctly storing data involves a two-phase process. First, a vanilla proof is generated: a CPU-only computation that reads the sealed sector data from disk, constructs Merkle inclusion proofs for the challenged leaf positions, and produces a set of cryptographic commitments. This vanilla proof is then fed into the second phase: a SNARK proof (specifically, a Groth16 proof over the BLS12-381 curve) that compresses the vanilla proof into a compact, verifiable certificate. The SNARK phase is GPU-accelerated and memory-intensive, consuming up to 200 GiB of RAM for 32 GiB sectors.

The cuzk project aims to build a persistent proving daemon that pipelines these phases, keeping the GPU hot and eliminating redundant I/O and SRS (Structured Reference String) loading overhead. Phase 1 of the project focused on building the daemon infrastructure: the gRPC API, the priority scheduler, the multi-GPU worker pool, and the observability stack. But to test and benchmark Phase 2—the pipelined prover that splits synthesis from GPU computation—the team needed realistic vanilla proof test data. This is what the gen-vanilla command provides.

The message is thus a validation milestone. The assistant has spent the preceding messages (msg 355 through 383) implementing the gen-vanilla subcommand in the cuzk-bench tool, adding filecoin-proofs-api as an optional dependency, writing CID commitment parsing logic, and wiring up three sub-subcommands for WinningPoSt, WindowPoSt, and SnapDeals. Each of those earlier steps involved decisions, debugging, and fixes. Message 384 is the moment where all that work is put to the test against real data.

The Sequential Validation Strategy

The assistant's approach reveals a deliberate testing methodology. Rather than running all three proof types in parallel or testing only the most complex case, the assistant validates them in order of increasing complexity:

WinningPoSt (msg 383): 1 sector, 66 challenges, 164 KB proof — the simplest case, testing basic Merkle inclusion proof generation.
WindowPoSt (msg 383): 1 sector, 10 challenges, 25 KB proof — still simple but uses a different proof type and challenge derivation.
SnapDeals (msg 384): 16 partitions, ~562 KB each, 12 MB total — the most complex case, involving sector updates, replica data, and multiple commitments. This incremental strategy is a classic debugging and validation technique: verify the simple cases first to build confidence in the underlying machinery, then tackle the complex case. If SnapDeals had failed, the assistant would know that the WinningPoSt and WindowPoSt paths work correctly, narrowing the bug search to the SnapDeals-specific logic (the additional commitment parameters, the replica handling, or the partition iteration). The assistant's opening line — "WindowPoSt vanilla generation works. 24.9 KB vanilla proof, 10 challenges. Now SnapDeals:" — serves as a checkpoint summary, explicitly recording the successful result before moving on. This is characteristic of a disciplined engineering workflow: documenting what works before attempting the next step.## Input Knowledge Required to Understand This Message A reader encountering this message must understand several layers of context. First, the Filecoin proof system itself: the distinction between vanilla proofs (CPU-only Merkle inclusion proofs) and SNARK proofs (GPU-accelerated Groth16 proofs), and the three proof types—WinningPoSt (elected sector challenges for block rewards), WindowPoSt (periodic sector audits), and SnapDeals (sector update proofs). Second, the cuzk project's architecture: that it is a persistent proving daemon being built in phases, with Phase 1 delivering the daemon infrastructure and Phase 2 targeting a pipelined prover that splits circuit synthesis from GPU computation. Third, the golden test data at /data/32gbench/: a 32 GiB sealed sector file, its Merkle tree cache, an update replica for SnapDeals testing, and text files containing commitment CIDs. The command-line invocation itself encodes significant domain knowledge. The FIL_PROOFS_PARAMETER_CACHE environment variable points to the directory containing the Groth16 proving parameters (the 32 GiB parameter file that was fetched in an earlier segment). The --orig-commdr and --update-commdr flags accept commitment CIDs—Filecoin-specific content identifiers that encode 32-byte Pedersen commitments using base32 encoding with a multibase prefix. The --sector-key and --replica flags point to the sealed sector data and the updated replica respectively, while the --*-cache flags point to Merkle tree cache directories that accelerate tree traversal during proof generation.

The Assumptions Embedded in This Message

The assistant makes several assumptions in this message, most of which are justified by prior work but worth examining. The primary assumption is that the golden test data at /data/32gbench/ is correctly structured and internally consistent—that the commdr.txt commitment matches the sealed sector's Merkle root, that the update-commdr.txt matches the replica, and that the cache directories contain valid pre-computed Merkle tree data. If any of these were corrupted or mismatched, the proof generation would either fail or produce invalid proofs, but the assistant would have no way to detect this without cross-validation against known-good outputs.

A second assumption is that the release build of cuzk-bench is correct—that the gen-vanilla feature flag properly gates the filecoin-proofs-api dependency, that the CID parsing logic correctly decodes the commitment strings, and that the subcommand dispatch correctly maps CLI arguments to the underlying API function calls. The assistant has verified compilation and unit tests (msg 375-377), but integration testing against real data is the true validation.

A third assumption is that the SnapDeals proof type (StackedDrg32GiBV1) is the correct circuit for the golden test data. The assistant is inferring the proof type from the sector size (32 GiB) and the operation (sector update). If the golden data were generated with a different circuit variant, the proof generation might produce structurally valid but semantically incorrect outputs.

The Output Knowledge Created

This message produces several forms of knowledge. Most immediately, it confirms that the SnapDeals vanilla proof generation pipeline works end-to-end: the tool reads the sealed sector and replica from disk, parses the commitment CIDs, invokes the filecoin-proofs-api vanilla proof functions, and serializes the results as base64-encoded JSON. The output file /tmp/snap-vanilla.json is a concrete artifact that can be consumed by the bench tool's --vanilla flag for Phase 2 testing.

Beyond the immediate output, the message creates confidence in the Phase 1 deliverable. The assistant has now validated all three proof types against real 32 GiB data, demonstrating that the gen-vanilla command is production-ready. This confidence is the foundation for the next major effort: Phase 2's pipelined prover implementation. The message also implicitly validates the CID parsing approach (manual base32 decoding via the cid crate), the feature-gating strategy (keeping filecoin-proofs-api optional to avoid bloating the default build), and the overall architectural decision to build a separate bench tool rather than embedding test data generation in the core daemon.

The Thinking Process Visible in the Message

While the message itself is terse—a bash command and its output—the thinking process is visible in its structure. The assistant has chosen to run the SnapDeals command after confirming WinningPoSt and WindowPoSt work, revealing a methodical, risk-averse mindset. The command is fully specified with absolute paths, indicating a desire for reproducibility and clarity. The use of 2>&1 (redirecting stderr to stdout) ensures that any error messages are captured in the output, not lost to the terminal. The FIL_PROOFS_PARAMETER_CACHE environment variable is set explicitly, acknowledging that the proving parameters are not in the default location and must be pointed to.

The assistant also chooses to display the parsed commitment values (comm_r_old, comm_r_new, comm_d_new) as hex strings in the output. This is not strictly necessary for the validation—the tool could have silently consumed them—but displaying them serves as a visual sanity check. The developer (or the assistant itself in a subsequent reasoning step) can compare these hex values against known-good commitments to verify that the CID parsing worked correctly. This is a subtle but important engineering practice: show your intermediate values to enable manual verification.

The Broader Significance

Message 384 is, on its face, a routine test execution. But within the arc of the cuzk project, it marks the completion of Phase 1's final deliverable. The subsequent message (msg 385) confirms the results with a summary table, and the assistant then commits the milestone and pivots to Phase 2—analyzing bellperson internals, designing the pipelined prover architecture, and creating a minimal fork to expose the synthesis/GPU split APIs. Without this validation, the Phase 2 work would be built on untested foundations.

The message also exemplifies a key principle of the cuzk project's methodology: validate against real data early. Rather than writing unit tests in isolation and hoping they generalize, the assistant repeatedly tests against the golden 32 GiB dataset that represents actual Filecoin sector data. This catches real-world issues—incorrect cache paths, mismatched commitment formats, unexpected proof sizes—that pure unit tests would miss. The gen-vanilla command itself is a tool built for this purpose: generate test data from real sectors, then use that data to drive the Phase 2 pipelined prover development.

In summary, message 384 is the moment where Phase 1's implementation work meets reality and is confirmed correct. It is a quiet but essential milestone in a larger engineering effort—a checkpoint that says "this works, now we can build the next thing on top of it."