fix: Broadcasting unconstrained function with empty sibling

[spalladino]

We were accidentally removing zero elements from the beginning of the sibling path when broadcasting unconstrained functions. Looking at the logs from failed runs, it seems to be the culprit:

2024-03-25 14:15:00 sandbox_1     |   aztec:circuits:artifact_hash TRACE Computed artifact hash artifactHash=0x05ec36f43999f40c957a0ed86659191680430fc1c9f2c451a1cfea8b71f0d7e0 privateFunctionRoot=0x2183eee0e130f895c25e3cda8b7f3b367baeb0bca0ddf5689ac6979da1e8cdb0 unconstrainedFunctionRoot=0x2b65d4d40fae120ec8738725cec71ffb4e340d1a17f678e7b03c1ab05e646210 metadataHash=0x229d43c7daac528d0aefd72bee59385d7e9ff06ea477b673389e1f65168cba9f +0ms

2024-03-25 14:15:17 end-to-end_1  |   aztec:circuits:function_membership_proof TRACE Computed proof for unconstrained function with selector 0xcff0a264 functionArtifactHash=0x26d3bd465a183b367291552b08bd192043bebb5d7b07b6f8b7d43432d74af09b functionMetadataHash=0x1a8b89c75f0ad79c19ba53a8bdfcb25bd4f8d33bfa11f1f52528a8ee58fc2543 artifactMetadataHash=0x229d43c7daac528d0aefd72bee59385d7e9ff06ea477b673389e1f65168cba9f artifactFunctionTreeSiblingPath=0x0000000000000000000000000000000000000000000000000000000000000000,0x01c398cebbd80cad3c89750c7523a853883c54d2248d7f5c634b50b1cf282422 privateFunctionsArtifactTreeRoot=0x2183eee0e130f895c25e3cda8b7f3b367baeb0bca0ddf5689ac6979da1e8cdb0 +0ms

2024-03-25 14:15:23 sandbox_1     |   aztec:circuits:function_membership_proof TRACE Artifact hash mismatch expected=0x05ec36f43999f40c957a0ed86659191680430fc1c9f2c451a1cfea8b71f0d7e0 computedArtifactHash=0x16fcaee22ed912eb011b05ec01cc8bb34a189fe162f122918cc1aa141ec3cc77 computedFunctionArtifactHash=0x26d3bd465a183b367291552b08bd192043bebb5d7b07b6f8b7d43432d74af09b computedArtifactFunctionTreeRoot=0x22266dee73fdd82ff937cd96df83d2d3f96a833978c639289146aa82eceaf305 privateFunctionsArtifactTreeRoot=0x2183eee0e130f895c25e3cda8b7f3b367baeb0bca0ddf5689ac6979da1e8cdb0 metadataHash=0x229d43c7daac528d0aefd72bee59385d7e9ff06ea477b673389e1f65168cba9f artifactFunctionTreeSiblingPath=0x01c398cebbd80cad3c89750c7523a853883c54d2248d7f5c634b50b1cf282422 +0ms

Note how the artifactFunctionTreeSiblingPath starts with a zero when computing the proof, but that's missing when verifying it.

[spalladino]

To the reviewer: this is the only real logic change in this PR

[PhilWindle]

Suggested change

	it('filters out zero-elements at the end of the artifcat tree sibling path', () => {
	it('filters out zero-elements at the end of the artifact tree sibling path', () => {

[AztecBot]

Benchmark results

Metrics with a significant change:

• note_successful_decrypting_time_in_ms (8): 214 (+29%)

Detailed results

All benchmarks are run on txs on the Benchmarking contract on the repository. Each tx consists of a batch call to create_note and increment_balance, which guarantees that each tx has a private call, a nested private call, a public call, and a nested public call, as well as an emitted private note, an unencrypted log, and public storage read and write.

This benchmark source data is available in JSON format on S3 here.

Values are compared against data from master at commit 2136a66c and shown if the difference exceeds 1%.

L2 block published to L1

Each column represents the number of txs on an L2 block published to L1.

Metric	8 txs	32 txs	64 txs
l1_rollup_calldata_size_in_bytes	676	676	676
l1_rollup_calldata_gas	6,412	6,400	6,400
l1_rollup_execution_gas	585,745	585,733	585,733
l2_block_processing_time_in_ms	1,354 (+4%)	4,734	9,111
note_successful_decrypting_time_in_ms	⚠️ 214 (+29%)	513 (-1%)	964 (-3%)
note_trial_decrypting_time_in_ms	19.9 (-71%)	29.6 (-11%)	93.3 (-23%)
l2_block_building_time_in_ms	16,996 (-3%)	63,723 (-1%)	127,424 (-3%)
l2_block_rollup_simulation_time_in_ms	7,936	27,832 (-1%)	55,495 (+1%)
l2_block_public_tx_process_time_in_ms	9,042 (-5%)	35,838 (-1%)	71,836 (-7%)

L2 chain processing

Each column represents the number of blocks on the L2 chain where each block has 16 txs.

Metric	5 blocks	10 blocks
node_history_sync_time_in_ms	14,247 (+4%)	27,581 (-2%)
note_history_successful_decrypting_time_in_ms	1,275 (+3%)	2,522 (+4%)
note_history_trial_decrypting_time_in_ms	104 (+25%)	159 (+5%)
node_database_size_in_bytes	18,636,880	35,020,880
pxe_database_size_in_bytes	29,859	59,414

Circuits stats

Stats on running time and I/O sizes collected for every circuit run across all benchmarks.

Circuit	circuit_simulation_time_in_ms	circuit_input_size_in_bytes	circuit_output_size_in_bytes
private-kernel-init	239 (+1%)	44,377	28,214
private-kernel-ordering	212	52,880	14,296
base-parity	4,663 (+5%)	128	311
root-parity	1,692 (+1%)	1,244	311
base-rollup	17,916	165,760	861
root-rollup	50.3	4,359	725
private-kernel-inner	601	73,794	28,214
public-kernel-app-logic	393 (-2%)	35,251	28,217
public-kernel-tail	171 (-2%)	40,928	28,217
merge-rollup	8.86 (+3%)	2,568	861

Tree insertion stats

The duration to insert a fixed batch of leaves into each tree type.

Metric	1 leaves	16 leaves	64 leaves	128 leaves	512 leaves	1024 leaves	2048 leaves	4096 leaves	32 leaves
batch_insert_into_append_only_tree_16_depth_ms	9.99	16.0	N/A	N/A	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_count	16.8	31.6	N/A	N/A	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_ms	0.582	0.494	N/A	N/A	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_32_depth_ms	N/A	N/A	46.3 (+1%)	72.4	230	445	868	1,718	N/A
batch_insert_into_append_only_tree_32_depth_hash_count	N/A	N/A	96.0	159	543	1,055	2,079	4,127	N/A
batch_insert_into_append_only_tree_32_depth_hash_ms	N/A	N/A	0.475	0.447	0.419	0.416	0.414	0.412 (-1%)	N/A
batch_insert_into_indexed_tree_20_depth_ms	N/A	N/A	53.8	106 (-2%)	333 (-2%)	661	1,302 (-2%)	2,604 (-1%)	N/A
batch_insert_into_indexed_tree_20_depth_hash_count	N/A	N/A	104	207	691	1,363	2,707	5,395	N/A
batch_insert_into_indexed_tree_20_depth_hash_ms	N/A	N/A	0.479	0.480 (-1%)	0.454 (-3%)	0.455	0.453 (-2%)	0.452 (-2%)	N/A
batch_insert_into_indexed_tree_40_depth_ms	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	61.4 (-1%)
batch_insert_into_indexed_tree_40_depth_hash_count	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	109
batch_insert_into_indexed_tree_40_depth_hash_ms	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	0.537 (-1%)

Miscellaneous

Transaction sizes based on how many contract classes are registered in the tx.

Metric	0 registered classes	1 registered classes
tx_size_in_bytes	14,966	494,914

Transaction processing duration by data writes.

Metric	0 new note hashes	1 new note hashes
tx_pxe_processing_time_ms	3,063 (-1%)	1,632

Metric	0 public data writes	1 public data writes
tx_sequencer_processing_time_ms	16.8 (+15%)	1,127 (-1%)