Initial FOIL implemenation.

Cargo.toml

@@ -109,7 +109,7 @@ flamegraph = ["pprof/flamegraph", "pprof/criterion"]
 
 [workspace]
 resolver = "2"
-members = ["lurk-macros", "lurk-metrics"]
+members = ["foil", "lurk-macros", "lurk-metrics"]
 
 # Dependencies that should be kept in sync through the whole workspace
 [workspace.dependencies]

foil/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "foil"
+version = "0.1.0"
+edition = "2021"
+authors = ["porcuquine <porcuquine@gmail.com>"]
+description = "Flat Optimization Intermediate Language"
+repository = "https://github.com/lurk-lab/lurk-rs"
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = { workspace = true }
+bellpepper = { workspace = true }
+bellpepper-core = { workspace = true }
+ff = { workspace = true }
+indexmap = { version = "1.9.3", features = ["rayon"] }
+generic-array = "0.14.7"
+lurk = { path = "../" }
+lurk-macros = { path = "../lurk-macros" }
+tracing = { workspace = true }
+neptune = { workspace = true, features = ["arity2","arity4","arity8","arity16","pasta","bls"] }
+once_cell = { workspace = true }
+pasta_curves = { workspace = true, features = ["repr-c", "serde"] }
+pretty_env_logger = "0.4"
+
+[dev-dependencies]
+env_logger = "*"
+test-log = "0.2.12"

foil/src/circuit.rs

@@ -0,0 +1,129 @@
+//! This module provides a general mechanism for synthesizing a circuit for a minimized Foil instance.
+
+use std::collections::HashSet;
+use std::fmt::Debug;
+
+use bellpepper::gadgets::num::AllocatedNum;
+use bellpepper_core::{Circuit, ConstraintSystem, SynthesisError};
+
+use crate::{Id, MappedFoil, MetaData, MetaMapper};
+use lurk::field::LurkField;
+
+pub trait Relation<F: LurkField>: Debug {
+    fn synthesize<CS: ConstraintSystem<F>>(
+        &self,
+        _cs: &mut CS,
+        _allocated_head: AllocatedNum<F>,
+        _successors: Vec<AllocatedNum<F>>,
+    ) -> Result<(), SynthesisError> {
+        unimplemented!()
+    }
+}
+
+// This is an incomplete schematic sketch of what synthesis should entail. NOTE: the simplicity and uniformity of this
+// last-mile conversion to a circuit. Most circuit-specific heavy lifting will be concentrated in the individual
+// `Relation` implementations.
+impl<T: PartialEq + Clone, F: LurkField, M: MetaData, R: Relation<F>, MR: MetaMapper<M, R>>
+    Circuit<F> for MappedFoil<T, M, R, MR>
+{
+    fn synthesize<CS: ConstraintSystem<F>>(self, cs: &mut CS) -> Result<(), SynthesisError> {
+        let foil = self.foil;
+        assert!(
+            foil.is_minimized(),
+            "only minimized Foils can be synthesized"
+        );
+
+        let partition = foil.graph.partition();
+        let _classes = partition.classes().clone();
+
+        let allocated = foil
+            .graph
+            .vertices()
+            .iter()
+            .enumerate()
+            .map(|(i, vertex)| {
+                AllocatedNum::alloc(
+                    &mut cs.namespace(|| format!("allocated-{i}-{vertex}")),
+                    //|| todo!("get from witness, calculate, or get as constant..."),
+                    || Ok(F::ZERO), // Just for initial testing.
+                )
+            })
+            .collect::<Result<Vec<_>, SynthesisError>>()?;
+
+        let mut constrained: HashSet<Id> = Default::default();
+        // for constructor in foil.schema.constructors.iter() {
+        //     let _projectors = constructor.projectors();
+        //     todo!();
+        // }
+
+        for (i, (representative_id, _)) in partition.classes.iter().enumerate() {
+            let vertex = foil.graph.vertex(*representative_id);
+            let allocated_head = allocated[i].clone();
+
+            //if todo!("determine whether this vertex requires allocation") {
+            if true {
+                // For example, projectors do not require allocation given that they will be constrained by their
+                // corresponding constructor. This *could* be handled at the `Relation` level, however, in general this
+                // decision may require more global context -- so for now, consider that it should be made in the
+                // top-level `synthesize` method.
+
+                // Currently, so-called `Bindings` (equivalences specified through the graph) become trivial after
+                // finalization. There is no reason to allocate variables for them or add any related constraints. The
+                // right answer is probably that minimization should remove them -- along with any other superfluous
+                // nodes of the graph.
+                //
+                // The point is that some parts of the decision (whether a given vertex needs constraints of its own)
+                // should probably be handled upstream. What is important is that we clearly understand the separation
+                // of concerns -- so decisions at each stage do not rely on invalid assumptions about the
+                // responsibilities of others. Some redundancy may therefore be appropriate.
+                //
+                // For example, in the case of bindings, all of the following could be implemented:
+                //
+                // - A full 'minimization' can remove them (with a check to ensure they were indeed enforced -- which
+                // means their successors have been made equivalent). This implies that the bindings themselves will not
+                // be seen here.
+
+                // - If they do appear here, we can detect that and not allocate or constrain them. However, note that
+                // maybe this is the wrong approach -- since it will require increasing knowledge of semantics here. Not
+                // special-casing would be simplest. One answer is to ensure that `Func`s can be defined in such a way
+                // as to provide hints here. Designation of `Bindings` (in the constructors example) as `equivalences`
+                // is effectively such an annotation, but it may be useful to provide a more general (probably
+                // trait-based) mechanism.
+                //
+                // - If we do reach the point of constraining such nodes, their defined `Relation::synthesize` method
+                // can be a no-op.
+
+                constrained.insert(*representative_id);
+
+                let allocated_successors = vertex
+                    .successors()
+                    .borrow()
+                    .iter()
+                    .map(|successor_id| {
+                        constrained.insert(*successor_id);
+                        allocated[*successor_id].clone()
+                    })
+                    .collect::<Vec<_>>();
+
+                let relation = {
+                    self.mapper
+                        .find(vertex.metadata())
+                        .unwrap_or_else(|| panic!("relation missing for {:?}", vertex.metadata()))
+                };
+
+                dbg!(relation);
+
+                relation.synthesize(
+                    &mut cs.namespace(|| format!("relation-{}", i)),
+                    allocated_head,
+                    allocated_successors,
+                )?;
+            }
+        }
+
+        // Every allocation has been constrained.
+        assert_eq!(constrained.len(), partition.size());
+
+        Ok(())
+    }
+}