Implement Small-Value Sum-Check Optimization (Algorithm 6)

examples/compute_barrett_constants.rs

@@ -0,0 +1,81 @@
+//! Compute Barrett reduction constants for Pallas Fp.
+//! Run with: cargo run --example compute_barrett_constants
+
+use num_bigint::BigUint;
+use num_traits::{One, ToPrimitive};
+use tracing::info;
+use tracing_subscriber::EnvFilter;
+
+fn main() {
+  tracing_subscriber::fmt()
+    .with_target(false)
+    .with_ansi(true)
+    .with_env_filter(EnvFilter::from_default_env())
+    .init();
+
+  // Pallas Fp modulus (base field)
+  let p = BigUint::parse_bytes(
+    b"40000000000000000000000000000000224698fc094cf91b992d30ed00000001",
+    16,
+  )
+  .unwrap();
+
+  // Barrett parameters
+  let np = 255u32; // bit-length of p
+  let r_prime = BigUint::one() << np; // R' = 2^255
+  let r = BigUint::one() << 64u32; // r = 2^64
+
+  // Compute constants
+  let two_p = &p * 2u32;
+  let mu = (&r * &r_prime) / &two_p;
+  let two_pow_64_mod_p = (BigUint::one() << 64u32) % &p;
+
+  // Log as structured data
+  info!(field = "Pallas Fp (Base field)", modulus = %format!("0x{:x}", p), "Barrett constants");
+  log_const("PALLAS_FP", &p, 4);
+  log_const("PALLAS_FP_2P", &two_p, 5);
+  log_const("PALLAS_FP_MU", &mu, 5);
+  log_const("TWO_POW_64_MOD_FP", &two_pow_64_mod_p, 4);
+
+  // Also compute Fq constants
+  compute_pallas_fq();
+
+  // Print final summary
+  println!("\nBarrett constants computed successfully. Run with RUST_LOG=info to see values.");
+}
+
+fn log_const(name: &str, value: &BigUint, num_limbs: usize) {
+  let limbs: Vec<u64> = (0..num_limbs)
+    .map(|i| {
+      let shifted = value >> (64 * i);
+      let masked = &shifted & BigUint::from(u64::MAX);
+      masked.to_u64().unwrap_or(0)
+    })
+    .collect();
+
+  info!(name = name, num_limbs = num_limbs, limbs = ?limbs, "computed constant");
+}
+
+// Also compute for Pallas Fq (scalar field) = Vesta Fp
+fn compute_pallas_fq() {
+  // Pallas Fq modulus (scalar field)
+  let q = BigUint::parse_bytes(
+    b"40000000000000000000000000000000224698fc0994a8dd8c46eb2100000001",
+    16,
+  )
+  .unwrap();
+
+  let nq = 255u32;
+  let r_prime = BigUint::one() << nq;
+  let r = BigUint::one() << 64u32;
+
+  let two_q = &q * 2u32;
+  let mu = (&r * &r_prime) / &two_q;
+  let two_pow_64_mod_q = (BigUint::one() << 64u32) % &q;
+
+  info!(field = "Pallas Fq (Scalar field)", modulus = %format!("0x{:x}", q), "Barrett constants");
+  log_const("PALLAS_FQ", &q, 4);
+  log_const("PALLAS_FQ_2Q", &two_q, 5);
+  log_const("PALLAS_FQ_MU", &mu, 5);
+  log_const("TWO_POW_64_MOD_FQ", &two_pow_64_mod_q, 4);
+}