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Merkle tree for custom predicate batches (#471)

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Resolve https://github.com/0xPARC/pod2/issues/466

Now batches are identified by the root of a merkle tree that contains all the predicates (using sequential indices as keys).  This means that the format to identify a custom predicate reference is still a hash + index, but the calculation of the hash is different.
The MainPod circuit now isn't limited by number of batches but instead number of custom predicates; and for each one we verify a merkle proof to verify the batch id.

I've removed a bunch of tests from lang that were testing splitting into multiple batches because there's no longer any need for that.  In a future PR we'll remove the code that handles batch splitting.

Each custom predicate needs 148.2 gates (which is very close to my estimate of 142.7 in https://github.com/0xPARC/pod2/issues/466#issuecomment-3823531286 where I actually made a mistake and considered 5 predicates per batch instead of 4 in the previous Params).
This commit is contained in:
Eduard S. 2026-02-04 11:12:32 +01:00 • committed by GitHub
parent a7a30176a7
commit 641d8dabdd
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17 changed files with 331 additions and 761 deletions
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42
src/lang/mod.rs
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@ -162,7 +162,7 @@ mod tests {
let request_result = processed.request.templates();
assert_eq!(request_result.len(), 0);
assert_eq!(batch_result.predicates.len(), 1);
assert_eq!(batch_result.predicates().len(), 1);
// Expected structure
let expected_statements = vec![StatementTmpl {
@ -179,11 +179,8 @@ mod tests {
2, // args_len (PodA, PodB)
names(&["PodA", "PodB"]),
)?;
let expected_batch = CustomPredicateBatch::new(
&params,
"PodlangBatch".to_string(),
vec![expected_predicate],
);
let expected_batch =
CustomPredicateBatch::new("PodlangBatch".to_string(), vec![expected_predicate]);
assert_eq!(*batch_result, expected_batch);
@ -244,7 +241,7 @@ mod tests {
let request_result = processed.request.templates();
assert_eq!(request_result.len(), 0);
assert_eq!(batch_result.predicates.len(), 1);
assert_eq!(batch_result.predicates().len(), 1);
// Expected structure: Public args: A (index 0). Private args: Temp (index 1)
let expected_statements = vec![
@ -270,11 +267,8 @@ mod tests {
1, // args_len (A)
names(&["A", "Temp"]),
)?;
let expected_batch = CustomPredicateBatch::new(
&params,
"PodlangBatch".to_string(),
vec![expected_predicate],
);
let expected_batch =
CustomPredicateBatch::new("PodlangBatch".to_string(), vec![expected_predicate]);
assert_eq!(*batch_result, expected_batch);
@ -298,7 +292,7 @@ mod tests {
let batch_result = first_batch(&processed);
let request_templates = processed.request.templates();
assert_eq!(batch_result.predicates.len(), 1);
assert_eq!(batch_result.predicates().len(), 1);
assert!(!request_templates.is_empty());
// Expected Batch structure
@ -316,11 +310,8 @@ mod tests {
2, // args_len (X, Y)
names(&["X", "Y"]),
)?;
let expected_batch = CustomPredicateBatch::new(
&params,
"PodlangBatch".to_string(),
vec![expected_predicate],
);
let expected_batch =
CustomPredicateBatch::new("PodlangBatch".to_string(), vec![expected_predicate]);
assert_eq!(*batch_result, expected_batch);
@ -362,7 +353,7 @@ mod tests {
let batch_result = first_batch(&processed);
let request_templates = processed.request.templates();
assert_eq!(batch_result.predicates.len(), 1); // some_pred is defined
assert_eq!(batch_result.predicates().len(), 1); // some_pred is defined
assert!(!request_templates.is_empty());
// Expected Wildcard Indices in Request Scope:
@ -607,7 +598,7 @@ mod tests {
"Expected no request templates"
);
assert_eq!(
first_batch(&processed).predicates.len(),
first_batch(&processed).predicates().len(),
4,
"Expected 4 custom predicates"
);
@ -727,7 +718,6 @@ mod tests {
)?;
let expected_batch = CustomPredicateBatch::new(
&params,
"PodlangBatch".to_string(),
vec![
expected_friend_pred,
@ -766,7 +756,7 @@ mod tests {
names(&["A", "B"]),
)?;
let available_batch =
CustomPredicateBatch::new(&params, "MyBatch".to_string(), vec![imported_predicate]);
CustomPredicateBatch::new("MyBatch".to_string(), vec![imported_predicate]);
let available_batches = vec![available_batch.clone()];
// 2. Create the input string that uses the batch
@ -819,7 +809,7 @@ mod tests {
let pred3 = CustomPredicate::and(&params, "p3".into(), vec![], 1, names(&["D"]))?;
let available_batch =
CustomPredicateBatch::new(&params, "MyBatch".to_string(), vec![pred1, pred2, pred3]);
CustomPredicateBatch::new("MyBatch".to_string(), vec![pred1, pred2, pred3]);
let available_batches = vec![available_batch.clone()];
// 2. Create the input string that uses the batch with skips
@ -883,7 +873,7 @@ mod tests {
names(&["A", "B"]),
)?;
let available_batch =
CustomPredicateBatch::new(&params, "MyBatch".to_string(), vec![imported_predicate]);
CustomPredicateBatch::new("MyBatch".to_string(), vec![imported_predicate]);
let available_batches = vec![available_batch.clone()];
// 2. Create the input string that defines a new predicate using the imported one
@ -908,13 +898,13 @@ mod tests {
"No request should be defined"
);
assert_eq!(
first_batch(&processed).predicates.len(),
first_batch(&processed).predicates().len(),
1,
"Expected one custom predicate to be defined"
);
// 4. Check the resulting predicate definition
let defined_pred = &first_batch(&processed).predicates[0];
let defined_pred = &first_batch(&processed).predicates()[0];
assert_eq!(defined_pred.name, "wrapper_pred");
assert_eq!(defined_pred.statements.len(), 1);