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Remove one helper function

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Linda Guiga 2023-09-14 19:15:43 +01:00
parent 17f661f90f
commit 9ab8a11887
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1 changed files with 20 additions and 25 deletions
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45
evm/src/lookup.rs
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@ -30,7 +30,7 @@ impl Lookup {
pub(crate) fn num_helper_columns(&self, constraint_degree: usize) -> usize {
// One helper column for each column batch of size `constraint_degree-1`,
// then one column for the inverse of `table + challenge` and one for the `Z` polynomial.
ceil_div_usize(self.columns.len(), constraint_degree - 1) + 2
ceil_div_usize(self.columns.len(), constraint_degree - 1) + 1
}
}
@ -89,7 +89,7 @@ pub(crate) fn lookup_helper_columns<F: Field>(
for x in table.iter_mut() {
*x = challenge + *x;
}
helper_columns.push(F::batch_multiplicative_inverse(&table).into());
let table_inverse: Vec<F> = F::batch_multiplicative_inverse(&table).into();
// Compute the `Z` polynomial with `Z(1)=0` and `Z(gx) = Z(x) + sum h_i(x) - frequencies(x)g(x)`.
// This enforces the check from the paper, that the sum of the h_k(x) polynomials is 0 over H.
@ -99,11 +99,11 @@ pub(crate) fn lookup_helper_columns<F: Field>(
let mut z = Vec::with_capacity(frequencies.len());
z.push(F::ZERO);
for i in 0..frequencies.len() - 1 {
let x = helper_columns[..num_helper_columns - 2]
let x = helper_columns[..num_helper_columns - 1]
.iter()
.map(|col| col.values[i])
.sum::<F>()
- frequencies[i] * helper_columns[num_helper_columns - 2].values[i];
- frequencies[i] * table_inverse[i];
z.push(z[i] + x);
}
helper_columns.push(z.into());
@ -158,20 +158,17 @@ pub(crate) fn eval_lookups_checks<F, FE, P, S, const D: usize, const D2: usize>(
_ => todo!("Allow other constraint degrees."),
}
}
// Check that the penultimate helper column contains `1/(table+challenge)`.
let x = lookup_vars.local_values[start + num_helper_columns - 2];
let x = x * (vars.local_values[lookup.table_column] + challenge);
yield_constr.constraint(x - P::ONES);
// Check the `Z` polynomial.
let z = lookup_vars.local_values[start + num_helper_columns - 1];
let next_z = lookup_vars.next_values[start + num_helper_columns - 1];
let y = lookup_vars.local_values[start..start + num_helper_columns - 2]
let table_with_challenge = vars.local_values[lookup.table_column] + challenge;
let y = lookup_vars.local_values[start..start + num_helper_columns - 1]
.iter()
.fold(P::ZEROS, |acc, x| acc + *x)
- vars.local_values[lookup.frequencies_column]
* lookup_vars.local_values[start + num_helper_columns - 2];
yield_constr.constraint(next_z - z - y);
* table_with_challenge
- vars.local_values[lookup.frequencies_column];
yield_constr.constraint((next_z - z) * table_with_challenge - y);
start += num_helper_columns;
}
}
@ -224,23 +221,21 @@ pub(crate) fn eval_lookups_checks_circuit<
_ => todo!("Allow other constraint degrees."),
}
}
let x = lookup_vars.local_values[start + num_helper_columns - 2];
let tmp = builder.add_extension(vars.local_values[lookup.table_column], challenge);
let x = builder.mul_sub_extension(x, tmp, one);
yield_constr.constraint(builder, x);
let z = lookup_vars.local_values[start + num_helper_columns - 1];
let next_z = lookup_vars.next_values[start + num_helper_columns - 1];
let y = builder.add_many_extension(
&lookup_vars.local_values[start..start + num_helper_columns - 2],
let table_with_challenge =
builder.add_extension(vars.local_values[lookup.table_column], challenge);
let mut y = builder.add_many_extension(
&lookup_vars.local_values[start..start + num_helper_columns - 1],
);
let tmp = builder.mul_extension(
vars.local_values[lookup.frequencies_column],
lookup_vars.local_values[start + num_helper_columns - 2],
);
let y = builder.sub_extension(y, tmp);
let constraint = builder.sub_extension(next_z, z);
let constraint = builder.sub_extension(constraint, y);
y = builder.mul_extension(y, table_with_challenge);
y = builder.sub_extension(y, vars.local_values[lookup.frequencies_column]);
let mut constraint = builder.sub_extension(next_z, z);
constraint = builder.mul_extension(constraint, table_with_challenge);
constraint = builder.sub_extension(constraint, y);
yield_constr.constraint(builder, constraint);
start += num_helper_columns;
}