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Split memory values into 9 bit values. #29

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Jul 24, 2024
Merged

Split memory values into 9 bit values. #29

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14 changes: 7 additions & 7 deletions stwo_cairo_prover/src/components/memory/component.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,14 +30,14 @@ pub const MEMORY_LOOKUP_VALUE_1: &str = "MEMORY_LOOKUP_1";
pub const MEMORY_LOOKUP_VALUE_2: &str = "MEMORY_LOOKUP_2";
pub const MEMORY_LOOKUP_VALUE_3: &str = "MEMORY_LOOKUP_3";

pub const N_M31_IN_FELT252: usize = 21;
pub const MULTIPLICITY_COLUMN: usize = 22;
pub const N_M31_IN_FELT252: usize = 28;
pub const MULTIPLICITY_COLUMN_OFFSET: usize = N_M31_IN_FELT252 + 1;
// TODO(AlonH): Make memory size configurable.
pub const LOG_MEMORY_ADDRESS_BOUND: u32 = 3;
pub const MEMORY_ADDRESS_BOUND: usize = 1 << LOG_MEMORY_ADDRESS_BOUND;

/// Addresses are continuous and start from 0.
/// Values are Felt252 stored as `N_M31_IN_FELT252` M31 values (each value contain 12 bits).
/// Values are Felt252 stored as `N_M31_IN_FELT252` M31 values (each value containing 9 bits).
pub struct MemoryTraceGenerator {
// TODO(AlonH): Consider to change values to be Felt252.
pub values: Vec<[BaseField; N_M31_IN_FELT252]>,
Expand Down Expand Up @@ -104,7 +104,7 @@ impl ComponentTraceGenerator<CpuBackend> for MemoryTraceGenerator {
for (j, value) in values.iter().enumerate() {
trace[j + 1][i] = BaseField::from_u32_unchecked(value.0);
}
trace[MULTIPLICITY_COLUMN][i] = BaseField::from_u32_unchecked(*multiplicity);
trace[MULTIPLICITY_COLUMN_OFFSET][i] = BaseField::from_u32_unchecked(*multiplicity);
}

let domain = CanonicCoset::new(LOG_MEMORY_ADDRESS_BOUND).circle_domain();
Expand Down Expand Up @@ -142,7 +142,7 @@ impl ComponentTraceGenerator<CpuBackend> for MemoryTraceGenerator {
log_size,
);
let interaction_value =
last + (denom_inverses[index] * trace[MULTIPLICITY_COLUMN].values[index]);
last + (denom_inverses[index] * trace[MULTIPLICITY_COLUMN_OFFSET].values[index]);
logup_values[index] = interaction_value;
last = interaction_value;
}
Expand Down Expand Up @@ -207,7 +207,7 @@ impl Component for MemoryComponent {
let address_and_value: [SecureField; N_M31_IN_FELT252 + 1] =
std::array::from_fn(|i| mask[BASE_TRACE][i][0]);
let numerator = value * shifted_secure_combination(&address_and_value, alpha, z)
- mask[BASE_TRACE][MULTIPLICITY_COLUMN][0];
- mask[BASE_TRACE][MULTIPLICITY_COLUMN_OFFSET][0];
let denom = point_vanishing(constraint_zero_domain.at(0), point);
evaluation_accumulator.accumulate(numerator / denom);

Expand All @@ -227,7 +227,7 @@ impl Component for MemoryComponent {
SecureField::from_partial_evals(std::array::from_fn(|i| mask[INTERACTION_TRACE][i][1]));
let numerator = (value - prev_value)
* shifted_secure_combination(&address_and_value, alpha, z)
- mask[BASE_TRACE][22][0];
- mask[BASE_TRACE][MULTIPLICITY_COLUMN_OFFSET][0];
let denom = coset_vanishing(constraint_zero_domain, point)
/ point_excluder(constraint_zero_domain.at(0), point);
evaluation_accumulator.accumulate(numerator / denom);
Expand Down
7 changes: 4 additions & 3 deletions stwo_cairo_prover/src/components/memory/component_prover.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,8 @@ use stwo_prover::trace_generation::{BASE_TRACE, INTERACTION_TRACE};

use super::component::{
MemoryComponent, MEMORY_ALPHA, MEMORY_LOOKUP_VALUE_0, MEMORY_LOOKUP_VALUE_1,
MEMORY_LOOKUP_VALUE_2, MEMORY_LOOKUP_VALUE_3, MEMORY_Z, MULTIPLICITY_COLUMN, N_M31_IN_FELT252,
MEMORY_LOOKUP_VALUE_2, MEMORY_LOOKUP_VALUE_3, MEMORY_Z, MULTIPLICITY_COLUMN_OFFSET,
N_M31_IN_FELT252,
};

impl ComponentProver<CpuBackend> for MemoryComponent {
Expand Down Expand Up @@ -84,12 +85,12 @@ impl ComponentProver<CpuBackend> for MemoryComponent {

let first_point_numerator = accum.random_coeff_powers[2]
* (value * shifted_secure_combination(&address_and_value, alpha, z)
- trace_evals[BASE_TRACE][MULTIPLICITY_COLUMN][i]);
- trace_evals[BASE_TRACE][MULTIPLICITY_COLUMN_OFFSET][i]);

let last_point_numerator = accum.random_coeff_powers[1] * (value - lookup_value);
let step_numerator = accum.random_coeff_powers[0]
* ((value - prev_value) * shifted_secure_combination(&address_and_value, alpha, z)
- trace_evals[BASE_TRACE][MULTIPLICITY_COLUMN][i]);
- trace_evals[BASE_TRACE][MULTIPLICITY_COLUMN_OFFSET][i]);
accum.accumulate(
i,
first_point_numerator * first_point_denom_inverse
Expand Down
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