Enabler struct

stwo_cairo_prover/crates/prover/src/components/utils.rs

@@ -1,8 +1,9 @@
+use std::array;
 use std::mem::transmute;
 use std::simd::Simd;
 use std::sync::atomic::{AtomicU32, Ordering};
 
-use num_traits::One;
+use num_traits::{One, Zero};
 use stwo_prover::core::backend::simd::column::BaseColumn;
 use stwo_prover::core::backend::simd::conversion::Pack;
 use stwo_prover::core::backend::simd::m31::{PackedM31, N_LANES};
@@ -83,17 +84,37 @@ impl AtomicMultiplicityColumn {
     }
 }
 
-/// Generates a column for the given padding offset.
-/// The enabler column is a column of length next_power_of_two(padding_offset) where
+/// The enabler column is a column of length `padding_offset.next_power_of_two()` where
 /// 1. The first `padding_offset` elements set to 1;
 /// 2. Otherwise set to 0.
-pub fn gen_enabler_column(padding_offset: usize) -> BaseColumn {
-    let log_size = padding_offset.next_power_of_two().ilog2();
-    let mut res = BaseColumn::zeros(1 << log_size);
-    for i in 0..padding_offset {
-        res.set(i, M31::one());
+#[derive(Debug, Clone)]
+pub struct Enabler {
+    pub padding_offset: usize,
+}
+impl Enabler {
+    pub const fn new(padding_offset: usize) -> Self {
+        Self { padding_offset }
+    }
+
+    pub fn packed_at(&self, vec_row: usize) -> PackedM31 {
+        let packed_row_offset = vec_row * N_LANES;
+        PackedM31::from_array(array::from_fn(|i| {
+            if i < self.padding_offset - packed_row_offset {
+                M31::one()
+            } else {
+                M31::zero()
+            }
+        }))
+    }
+
+    pub fn gen_column_simd(&self) -> BaseColumn {
+        let log_size = self.padding_offset.next_power_of_two().ilog2();
+        let mut col = BaseColumn::zeros(1 << log_size);
+        for i in 0..self.padding_offset {
+            col.set(i, M31::one());
+        }
+        col
     }
-    res
 }
 
 #[cfg(test)]
@@ -124,10 +145,11 @@ mod tests {
     }
 
     #[test]
-    fn test_gen_enabler_column() {
+    fn test_enabler_column() {
         let n_calls = 30;
+        let padding = super::Enabler::new(n_calls);
 
-        let enabler_column = super::gen_enabler_column(n_calls);
+        let enabler_column = padding.gen_column_simd();
 
         for (i, val) in enabler_column.into_cpu_vec().into_iter().enumerate() {
             if i < n_calls {
@@ -137,4 +159,16 @@ mod tests {
             }
         }
     }
+
+    #[test]
+    fn test_enabler_packed_at() {
+        let n_calls = 30;
+        let padding = super::Enabler::new(n_calls);
+
+        assert_eq!(padding.packed_at(0).to_array(), [1; N_LANES].map(M31::from));
+        assert_eq!(
+            padding.packed_at(1).to_array(),
+            [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0].map(M31::from)
+        );
+    }
 }