From 56b62f19642303faeb149d1d459aee7cfb8438d0 Mon Sep 17 00:00:00 2001
From: Nicholas Ward <npward@berkeley.edu>
Date: Thu, 29 Jul 2021 10:26:46 -0700
Subject: [PATCH 1/3] new exp gate takes in CircuitConfig and determines
 num_bits

---
 src/gadgets/arithmetic.rs   |  2 +-
 src/gates/exponentiation.rs | 22 ++++++++++++++++++++--
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/gadgets/arithmetic.rs b/src/gadgets/arithmetic.rs
index 5597499d..bf16a820 100644
--- a/src/gadgets/arithmetic.rs
+++ b/src/gadgets/arithmetic.rs
@@ -178,7 +178,7 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         exponent_bits: impl Iterator<Item = impl Borrow<Target>>,
     ) -> Target {
         let exp_bits_vec: Vec<Target> = exponent_bits.map(|b| *b.borrow()).collect();
-        let gate = ExponentiationGate::new(exp_bits_vec.len());
+        let gate = ExponentiationGate::new(self.config.clone());
         let gate_index = self.add_gate(gate.clone(), vec![]);
 
         let two = self.constant(F::TWO);
diff --git a/src/gates/exponentiation.rs b/src/gates/exponentiation.rs
index 900559e6..a7cd8b1c 100644
--- a/src/gates/exponentiation.rs
+++ b/src/gates/exponentiation.rs
@@ -1,6 +1,7 @@
 use std::marker::PhantomData;
 
 use crate::circuit_builder::CircuitBuilder;
+use crate::circuit_data::CircuitConfig;
 use crate::field::extension_field::target::ExtensionTarget;
 use crate::field::extension_field::Extendable;
 use crate::field::field::Field;
@@ -20,7 +21,8 @@ pub(crate) struct ExponentiationGate<F: Extendable<D>, const D: usize> {
 }
 
 impl<F: Extendable<D>, const D: usize> ExponentiationGate<F, D> {
-    pub fn new(num_power_bits: usize) -> Self {
+    pub fn new(config: CircuitConfig) -> Self {
+        let num_power_bits = Self::max_power_bits(config.num_wires, config.num_routed_wires);
         Self {
             num_power_bits,
             _phantom: PhantomData,
@@ -281,9 +283,11 @@ mod tests {
 
     use rand::{thread_rng, Rng};
 
+    use crate::circuit_data::CircuitConfig;
     use crate::field::crandall_field::CrandallField;
     use crate::field::extension_field::quartic::QuarticCrandallField;
     use crate::field::field::Field;
+    use crate::fri::FriConfig;
     use crate::gates::exponentiation::ExponentiationGate;
     use crate::gates::gate::Gate;
     use crate::gates::gate_testing::test_low_degree;
@@ -311,7 +315,21 @@ mod tests {
 
     #[test]
     fn low_degree() {
-        test_low_degree::<CrandallField, _, 4>(ExponentiationGate::new(5));
+        let config = CircuitConfig {
+            num_wires: 120,
+            num_routed_wires: 30,
+            security_bits: 0,
+            rate_bits: 0,
+            num_challenges: 0,
+            zero_knowledge: false,
+            fri_config: FriConfig {
+                proof_of_work_bits: 0,
+                reduction_arity_bits: Vec::new(),
+                num_query_rounds: 0,
+            },
+        };
+
+        test_low_degree::<CrandallField, _, 4>(ExponentiationGate::new(config));
     }
 
     #[test]

From 8440a4cbdf50276bc38ecf52c5e32868a6df1e74 Mon Sep 17 00:00:00 2001
From: Nicholas Ward <npward@berkeley.edu>
Date: Thu, 29 Jul 2021 15:15:40 -0700
Subject: [PATCH 2/3] fix

---
 src/gadgets/arithmetic.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/gadgets/arithmetic.rs b/src/gadgets/arithmetic.rs
index a181cb80..bf3c188d 100644
--- a/src/gadgets/arithmetic.rs
+++ b/src/gadgets/arithmetic.rs
@@ -176,8 +176,12 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         base: Target,
         exponent_bits: impl Iterator<Item = impl Borrow<Target>>,
     ) -> Target {
-        let exp_bits_vec: Vec<Target> = exponent_bits.map(|b| *b.borrow()).collect();
         let gate = ExponentiationGate::new(self.config.clone());
+        let num_power_bits = gate.num_power_bits;
+        let mut exp_bits_vec: Vec<Target> = exponent_bits.map(|b| *b.borrow()).collect();
+        while exp_bits_vec.len() < num_power_bits {
+            exp_bits_vec.push(self.constant(F::ZERO));
+        }
         let gate_index = self.add_gate(gate.clone(), vec![]);
 
         self.route(base, Target::wire(gate_index, gate.wire_base()));

From 9eda81c293a17dbd30ce6e37b4f6f31a069f6188 Mon Sep 17 00:00:00 2001
From: Nicholas Ward <npward@berkeley.edu>
Date: Thu, 29 Jul 2021 15:31:04 -0700
Subject: [PATCH 3/3] minor changes

---
 src/gates/exponentiation.rs | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/src/gates/exponentiation.rs b/src/gates/exponentiation.rs
index ef1786f5..2f33e5d9 100644
--- a/src/gates/exponentiation.rs
+++ b/src/gates/exponentiation.rs
@@ -28,7 +28,7 @@ impl<F: Extendable<D>, const D: usize> ExponentiationGate<F, D> {
         }
     }
 
-    pub fn max_power_bits(num_wires: usize, num_routed_wires: usize) -> usize {
+    fn max_power_bits(num_wires: usize, num_routed_wires: usize) -> usize {
         let max_for_routed_wires = num_routed_wires - 3;
         let max_for_wires = (num_wires - 3) / 2;
         max_for_routed_wires.min(max_for_wires)
@@ -297,15 +297,7 @@ mod tests {
         let config = CircuitConfig {
             num_wires: 120,
             num_routed_wires: 30,
-            security_bits: 0,
-            rate_bits: 0,
-            num_challenges: 0,
-            zero_knowledge: false,
-            fri_config: FriConfig {
-                proof_of_work_bits: 0,
-                reduction_arity_bits: Vec::new(),
-                num_query_rounds: 0,
-            },
+            ..CircuitConfig::large_config()
         };
 
         test_low_degree::<CrandallField, _, 4>(ExponentiationGate::new(config));