docs: Describe the new message box model

[LHerskind]

Fixes #4250 and writes out an initial implementation of a solidity frontier tree.

[LHerskind]

Current dependencies on/for this PR:

• master
  • PR docs: Describe the new message box model #4485 👈

This stack of pull requests is managed by Graphite.

[AztecBot]

Benchmark results

Metrics with a significant change:

• note_trial_decrypting_time_in_ms (32): 103 (+143%)

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 bc25f9bd 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	128 txs
l1_rollup_calldata_size_in_bytes	45,700	180,580	720,100
l1_rollup_calldata_gas	222,832	871,420	3,466,276
l1_rollup_execution_gas	316,023	989,868	3,686,654
l2_block_processing_time_in_ms	1,164 (+1%)	4,331 (-1%)	17,244
note_successful_decrypting_time_in_ms	325 (+4%)	975 (-3%)	3,665
note_trial_decrypting_time_in_ms	36.3 (+35%)	⚠️ 103 (+143%)	158 (+11%)
l2_block_building_time_in_ms	17,812	70,198	281,756
l2_block_rollup_simulation_time_in_ms	13,091	51,576	207,549
l2_block_public_tx_process_time_in_ms	4,691	18,543	73,954

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	13,807 (+1%)	26,486
note_history_successful_decrypting_time_in_ms	2,389 (-6%)	4,808 (+3%)
note_history_trial_decrypting_time_in_ms	98.7 (-38%)	215 (+17%)
node_database_size_in_bytes	17,342,544	33,091,664
pxe_database_size_in_bytes	29,923	59,478

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	307	44,528	25,825
private-kernel-ordering	194	44,145	16,225
base-rollup	1,404	128,654	933
root-rollup	82.5	4,192	729
private-kernel-inner	435	71,331	25,825
public-kernel-private-input	241	32,287	25,825
public-kernel-non-first-iteration	237	32,329	25,825
merge-rollup	7.85	2,712	933

Tree insertion stats

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

Metric	1 leaves	2 leaves	8 leaves	16 leaves	32 leaves	128 leaves	64 leaves	512 leaves	1024 leaves	2048 leaves	8192 leaves
batch_insert_into_append_only_tree_16_depth_ms	10.2	11.2 (+6%)	12.8 (+2%)	17.0	22.7	64.2	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_count	16.9	17.5	23.0	31.6	47.0	143	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_ms	0.595	0.626 (+6%)	0.542 (+1%)	0.526	0.477	0.443	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_32_depth_ms	N/A	N/A	N/A	N/A	N/A	75.1	47.5	240 (+1%)	462	896 (-1%)	3,554
batch_insert_into_append_only_tree_32_depth_hash_count	N/A	N/A	N/A	N/A	N/A	159	96.0	543	1,055	2,079	8,223
batch_insert_into_append_only_tree_32_depth_hash_ms	N/A	N/A	N/A	N/A	N/A	0.464	0.487	0.437	0.432	0.427	0.428
batch_insert_into_indexed_tree_20_depth_ms	N/A	N/A	N/A	N/A	N/A	104	56.8 (+1%)	353 (+1%)	688	1,359 (-1%)	5,399
batch_insert_into_indexed_tree_20_depth_hash_count	N/A	N/A	N/A	N/A	N/A	197	104	691	1,363	2,707	10,771
batch_insert_into_indexed_tree_20_depth_hash_ms	N/A	N/A	N/A	N/A	N/A	0.496	0.498 (+1%)	0.475	0.473	0.472	0.471
batch_insert_into_indexed_tree_40_depth_ms	N/A	N/A	N/A	56.6	N/A	N/A	N/A	N/A	N/A	N/A	N/A
batch_insert_into_indexed_tree_40_depth_hash_count	N/A	N/A	N/A	94.1	N/A	N/A	N/A	N/A	N/A	N/A	N/A
batch_insert_into_indexed_tree_40_depth_hash_ms	N/A	N/A	N/A	0.578	N/A	N/A	N/A	N/A	N/A	N/A	N/A

Miscellaneous

Transaction sizes based on how many contracts are deployed in the tx.

Metric	0 deployed contracts	1 deployed contracts
tx_size_in_bytes	16,859	40,167

Transaction processing duration by data writes.

Metric	0 new commitments	1 new commitments
tx_pxe_processing_time_ms	553	1,306

Metric	0 public data writes	1 public data writes
tx_sequencer_processing_time_ms	0.497 (+3%)	576

[sklppy88]

This is super cool. The frontier tree is fascinating. I have a bunch of (highly) opinionated nits, feel free to ignore !

[sklppy88]

Suggested change

	This allows us to move a lot of messages at once without having to update a lot of storage making it cheaper to move messages independent on the number of messages.
	This allows us to move a lot of messages at once without having to update a lot of storage—making it cheaper to move messages independent on the number of messages.

[sklppy88]

Suggested change

	For a binary tree, we have that every `1` in the binary index represent a "right turn" down the tree.
	For a binary tree, we have that every `1` in the binary index represents a "right turn" down the tree.

[sklppy88]

Suggested change

	Then we know that anything that is at the right of the frontier have not yet been inserted, so all of these values are simply "zeros" values.
	Then we know that anything that is at the right of the frontier has not yet been inserted, so all of these values are simply "zeros" values.

[sklppy88]

Suggested change

	Zeros here understood as the root for a subtree only with zeros.
	Zeros here are understood as the root for a subtree only containing zeros.

[sklppy88]

Suggested change

	For example, if we take the tree from above and computes the root for it, we would see that level 2 was updated last.
	For example, if we take the tree from above and compute the root for it, we would see that level 2 was updated last.

[sklppy88]

Suggested change

	For cases where we have built further, we simple "walk" up the tree and use either the frontier value or the zero value for the level.
	For cases where we have built further, we simply "walk" up the tree and use either the frontier value or the zero value for the level.

[benesjan]

Cool way to test this 👍

[benesjan]

Very nice and thorough writeup! I don't see any issues with the design and Esau seem to have caught all the grammatical issues so feel free to merge once you address his comments. Frontier tree is very cool.