add "Optimal time we can hope for" in logup_star benchmark

Author: TomWambsgans

crates/lookup/src/logup_star.rs

@@ -256,6 +256,8 @@ pub fn compute_pushforward<F: PrimeField64, EF: ExtensionField<EF>>(
 
 #[cfg(test)]
 mod tests {
+    use std::time::Instant;
+
     use super::*;
     use p3_field::PrimeCharacteristicRing;
     use p3_koala_bear::{KoalaBear, QuinticExtensionFieldKB};
@@ -340,5 +342,22 @@ mod tests {
         for eval in &statements.on_pushforward {
             assert_eq!(pushforward.evaluate(&eval.point), eval.value);
         }
+
+        {
+            let n_muls = 20;
+            let slice = (0..(table_length + indexes_len) / packing_width::<EF>())
+                .map(|_| rng.random())
+                .collect::<Vec<EFPacking<EF>>>();
+            let time = Instant::now();
+            let sum = slice
+                .par_iter()
+                .map(|x| (0..n_muls).map(|_| *x).product::<EFPacking<EF>>())
+                .sum::<EFPacking<EF>>();
+            assert!(sum != EFPacking::<EF>::ZERO);
+            println!(
+                "Optimal time we can hope for: {} ms",
+                time.elapsed().as_millis()
+            );
+        }
     }
 }