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Documentation and variable naming cleanups. 

Co-authored-by: Daira Hopwood <daira@jacaranda.org>
This commit is contained in:
therealyingtong 2021-07-19 18:48:49 +08:00
parent fe95122ef7
commit c444ddebf8
1 changed files with 17 additions and 10 deletions
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27
src/circuit/gadget/utilities/decompose_running_sum.rs
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@ -9,9 +9,11 @@
//! The difference between each interstitial running sum output is constrained
//! to be $K$ bits, i.e.
//! `range_check`($k_i$, $2^K$),
//! where `range_check(word, range)
//! = word * (1 - word) * (2 - word) * ... * ((range - 1) - word)`
//! is an expression of degree range.
//! where
//! ```
//! range_check(word, range)
//! = word * (1 - word) * (2 - word) * ... * ((range - 1) - word)
//! ```
//!
//! Given that the `range_check` constraint will be toggled by a selector, in
//! practice we will have a `selector * range_check(word, range)` expression
@ -133,7 +135,14 @@ impl<F: FieldExt + PrimeFieldBits, const WINDOW_NUM_BITS: usize>
word_num_bits: usize,
num_windows: usize,
) -> Result<(CellValue<F>, RunningSum<F>), Error> {
let z_0 = copy(region, || "z_0 = alpha", self.z, offset, &alpha, &self.perm)?;
let z_0 = copy(
region,
|| "copy z_0 = alpha",
self.z,
offset,
&alpha,
&self.perm,
)?;
self.decompose(region, offset, z_0, strict, word_num_bits, num_windows)
}
@ -192,13 +201,11 @@ impl<F: FieldExt + PrimeFieldBits, const WINDOW_NUM_BITS: usize>
let mut zs: Vec<CellValue<F>> = Vec::with_capacity(num_windows);
let mut z = z_0;
// Assign running sum `z_i`, i = 0..=n, where z_{i+1} = (z_i - k_i) / (2^K).
// Assign running sum `z_{i+1}` = (z_i - k_i) / (2^K) for i = 0..=n-1.
// Outside of this helper, z_0 = alpha must have already been loaded into the
// `z` column at `offset`.
let offset = offset + 1;
let two_pow_k_inv = F::from_u64(1 << WINDOW_NUM_BITS as u64).invert().unwrap();
for (idx, word) in words.iter().enumerate() {
for (i, word) in words.iter().enumerate() {
// z_next = (z_cur - word) / (2^K)
let z_next = {
let word = word.map(|word| F::from_u64(word as u64));
@ -207,9 +214,9 @@ impl<F: FieldExt + PrimeFieldBits, const WINDOW_NUM_BITS: usize>
.zip(word)
.map(|(z_cur_val, word)| (z_cur_val - word) * two_pow_k_inv);
let cell = region.assign_advice(
|| format!("z_{:?}", idx + 1),
|| format!("z_{:?}", i + 1),
self.z,
offset + idx,
offset + i + 1,
|| z_next_val.ok_or(Error::SynthesisError),
)?;
CellValue::new(cell, z_next_val)