Add a simple metrics Recorder for counting things in models

Cargo.toml

@@ -35,5 +35,6 @@ harness = false
 [dependencies]
 subtle = "2.2.1"
 crossbeam-utils = "0.7"
+metrics = "0.13.0-alpha.8"
 num_cpus = "1.13"
 rand = "0.7"

src/lib.rs

@@ -18,3 +18,5 @@ pub mod plonk;
 pub mod poly;
 pub mod transcript;
 pub mod tweedle;
+
+pub mod model;

src/model.rs

@@ -0,0 +1,110 @@
+//! Helpers for modelling halo2 circuit performance.
+
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::fmt;
+use std::sync::Arc;
+
+use metrics::{Key, Recorder, Unit};
+
+/// A [`metrics`] recorder for examining halo2 metrics.
+///
+/// # Examples
+///
+/// ```
+/// use halo2::model::ModelRecorder;
+///
+/// fn main() {
+///     let recorder = Box::leak(Box::new(ModelRecorder::default()));
+///     metrics::set_recorder(recorder).unwrap();
+///
+///     // Create circuit, build and/or verify proof.
+///
+///     println!("{}", recorder);
+/// }
+/// ```
+#[derive(Debug)]
+pub struct ModelRecorder {
+    counters: Arc<RefCell<HashMap<Key, u64>>>,
+}
+
+impl Default for ModelRecorder {
+    fn default() -> Self {
+        ModelRecorder {
+            counters: Default::default(),
+        }
+    }
+}
+
+impl fmt::Display for ModelRecorder {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut counters = self
+            .counters
+            .try_borrow()
+            .unwrap()
+            .iter()
+            .map(|(k, v)| (k.clone(), *v))
+            .collect::<Vec<_>>();
+
+        counters.sort_by(|(k1, _), (k2, _)| {
+            let key1 = (
+                k1.name(),
+                k1.labels()
+                    .map(|l| (l.key(), l.value()))
+                    .collect::<Vec<_>>(),
+            );
+            let key2 = (
+                k2.name(),
+                k2.labels()
+                    .map(|l| (l.key(), l.value()))
+                    .collect::<Vec<_>>(),
+            );
+            key1.cmp(&key2)
+        });
+
+        writeln!(f, "Recorded metrics:")?;
+        for (key, value) in counters.iter() {
+            writeln!(f, "- {}: {}", key, value)?;
+        }
+        Ok(())
+    }
+}
+
+impl Recorder for ModelRecorder {
+    fn register_counter(&self, _key: Key, _unit: Option<Unit>, _description: Option<&'static str>) {
+    }
+
+    fn register_gauge(&self, _key: Key, _unit: Option<Unit>, _description: Option<&'static str>) {}
+
+    fn register_histogram(
+        &self,
+        _key: Key,
+        _unit: Option<Unit>,
+        _description: Option<&'static str>,
+    ) {
+    }
+
+    fn increment_counter(&self, key: Key, value: u64) {
+        *self
+            .counters
+            .try_borrow_mut()
+            .unwrap()
+            .entry(key)
+            .or_default() += value;
+    }
+
+    fn update_gauge(&self, _key: Key, _value: f64) {
+        unimplemented!()
+    }
+
+    fn record_histogram(&self, _key: Key, _value: u64) {
+        unimplemented!()
+    }
+}
+
+impl ModelRecorder {
+    /// Clear all recorded metrics.
+    pub fn clear(&self) {
+        self.counters.try_borrow_mut().unwrap().clear();
+    }
+}