mirror of
https://github.com/logos-storage/plonky2.git
synced 2026-01-02 13:53:07 +00:00
428 lines
16 KiB
Rust
428 lines
16 KiB
Rust
use std::marker::PhantomData;
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use itertools::unfold;
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use crate::field::extension_field::target::ExtensionTarget;
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use crate::field::extension_field::Extendable;
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use crate::field::field_types::{Field, RichField};
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use crate::gates::gate::Gate;
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use crate::iop::generator::{GeneratedValues, SimpleGenerator, WitnessGenerator};
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use crate::iop::target::Target;
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use crate::iop::wire::Wire;
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use crate::iop::witness::{PartitionWitness, Witness};
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use crate::plonk::circuit_builder::CircuitBuilder;
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use crate::plonk::vars::{EvaluationTargets, EvaluationVars, EvaluationVarsBase};
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/// Number of arithmetic operations performed by an arithmetic gate.
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pub const NUM_U32_ARITHMETIC_OPS: usize = 3;
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/// A gate to perform a basic mul-add on 32-bit values (we assume they are range-checked beforehand).
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#[derive(Clone, Debug)]
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pub struct U32ArithmeticGate<F: RichField + Extendable<D>, const D: usize> {
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_phantom: PhantomData<F>,
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}
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impl<F: RichField + Extendable<D>, const D: usize> U32ArithmeticGate<F, D> {
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pub fn new() -> Self {
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Self {
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_phantom: PhantomData,
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}
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}
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pub fn wire_ith_multiplicand_0(i: usize) -> usize {
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debug_assert!(i < NUM_U32_ARITHMETIC_OPS);
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5 * i
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}
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pub fn wire_ith_multiplicand_1(i: usize) -> usize {
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debug_assert!(i < NUM_U32_ARITHMETIC_OPS);
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5 * i + 1
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}
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pub fn wire_ith_addend(i: usize) -> usize {
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debug_assert!(i < NUM_U32_ARITHMETIC_OPS);
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5 * i + 2
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}
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pub fn wire_ith_output_low_half(i: usize) -> usize {
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debug_assert!(i < NUM_U32_ARITHMETIC_OPS);
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5 * i + 3
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}
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pub fn wire_ith_output_high_half(i: usize) -> usize {
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debug_assert!(i < NUM_U32_ARITHMETIC_OPS);
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5 * i + 4
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}
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pub fn limb_bits() -> usize {
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2
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}
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pub fn num_limbs() -> usize {
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64 / Self::limb_bits()
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}
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pub fn wire_ith_output_jth_limb(i: usize, j: usize) -> usize {
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debug_assert!(i < NUM_U32_ARITHMETIC_OPS);
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debug_assert!(j < Self::num_limbs());
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5 * NUM_U32_ARITHMETIC_OPS + Self::num_limbs() * i + j
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}
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}
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impl<F: RichField + Extendable<D>, const D: usize> Gate<F, D> for U32ArithmeticGate<F, D> {
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fn id(&self) -> String {
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format!("{:?}", self)
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}
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fn eval_unfiltered(&self, vars: EvaluationVars<F, D>) -> Vec<F::Extension> {
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let mut constraints = Vec::with_capacity(self.num_constraints());
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for i in 0..NUM_U32_ARITHMETIC_OPS {
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let multiplicand_0 = vars.local_wires[Self::wire_ith_multiplicand_0(i)];
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let multiplicand_1 = vars.local_wires[Self::wire_ith_multiplicand_1(i)];
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let addend = vars.local_wires[Self::wire_ith_addend(i)];
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let computed_output = multiplicand_0 * multiplicand_1 + addend;
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let output_low = vars.local_wires[Self::wire_ith_output_low_half(i)];
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let output_high = vars.local_wires[Self::wire_ith_output_high_half(i)];
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let base = F::Extension::from_canonical_u64(1 << 32u64);
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let combined_output = output_high * base + output_low;
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constraints.push(combined_output - computed_output);
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let mut combined_low_limbs = F::Extension::ZERO;
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let mut combined_high_limbs = F::Extension::ZERO;
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let midpoint = Self::num_limbs() / 2;
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let base = F::Extension::from_canonical_u64(1u64 << Self::limb_bits());
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for j in (0..Self::num_limbs()).rev() {
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let this_limb = vars.local_wires[Self::wire_ith_output_jth_limb(i, j)];
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let max_limb = 1 << Self::limb_bits();
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let product = (0..max_limb)
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.map(|x| this_limb - F::Extension::from_canonical_usize(x))
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.product();
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constraints.push(product);
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if j < midpoint {
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combined_low_limbs = base * combined_low_limbs + this_limb;
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} else {
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combined_high_limbs = base * combined_high_limbs + this_limb;
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}
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}
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constraints.push(combined_low_limbs - output_low);
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constraints.push(combined_high_limbs - output_high);
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}
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constraints
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}
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fn eval_unfiltered_base(&self, vars: EvaluationVarsBase<F>) -> Vec<F> {
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let mut constraints = Vec::with_capacity(self.num_constraints());
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for i in 0..NUM_U32_ARITHMETIC_OPS {
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let multiplicand_0 = vars.local_wires[Self::wire_ith_multiplicand_0(i)];
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let multiplicand_1 = vars.local_wires[Self::wire_ith_multiplicand_1(i)];
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let addend = vars.local_wires[Self::wire_ith_addend(i)];
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let computed_output = multiplicand_0 * multiplicand_1 + addend;
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let output_low = vars.local_wires[Self::wire_ith_output_low_half(i)];
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let output_high = vars.local_wires[Self::wire_ith_output_high_half(i)];
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let base = F::from_canonical_u64(1 << 32u64);
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let combined_output = output_high * base + output_low;
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constraints.push(combined_output - computed_output);
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let mut combined_low_limbs = F::ZERO;
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let mut combined_high_limbs = F::ZERO;
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let midpoint = Self::num_limbs() / 2;
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let base = F::from_canonical_u64(1u64 << Self::limb_bits());
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for j in (0..Self::num_limbs()).rev() {
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let this_limb = vars.local_wires[Self::wire_ith_output_jth_limb(i, j)];
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let max_limb = 1 << Self::limb_bits();
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let product = (0..max_limb)
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.map(|x| this_limb - F::from_canonical_usize(x))
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.product();
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constraints.push(product);
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if j < midpoint {
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combined_low_limbs = base * combined_low_limbs + this_limb;
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} else {
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combined_high_limbs = base * combined_high_limbs + this_limb;
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}
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}
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constraints.push(combined_low_limbs - output_low);
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constraints.push(combined_high_limbs - output_high);
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}
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constraints
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}
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fn eval_unfiltered_recursively(
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&self,
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builder: &mut CircuitBuilder<F, D>,
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vars: EvaluationTargets<D>,
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) -> Vec<ExtensionTarget<D>> {
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let mut constraints = Vec::with_capacity(self.num_constraints());
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for i in 0..NUM_U32_ARITHMETIC_OPS {
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let multiplicand_0 = vars.local_wires[Self::wire_ith_multiplicand_0(i)];
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let multiplicand_1 = vars.local_wires[Self::wire_ith_multiplicand_1(i)];
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let addend = vars.local_wires[Self::wire_ith_addend(i)];
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let computed_output = builder.mul_add_extension(multiplicand_0, multiplicand_1, addend);
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let output_low = vars.local_wires[Self::wire_ith_output_low_half(i)];
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let output_high = vars.local_wires[Self::wire_ith_output_high_half(i)];
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let base: F::Extension = F::from_canonical_u64(1 << 32u64).into();
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let base_target = builder.constant_extension(base);
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let combined_output = builder.mul_add_extension(output_high, base_target, output_low);
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constraints.push(builder.sub_extension(combined_output, computed_output));
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let mut combined_low_limbs = builder.zero_extension();
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let mut combined_high_limbs = builder.zero_extension();
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let midpoint = Self::num_limbs() / 2;
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let base = builder
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.constant_extension(F::Extension::from_canonical_u64(1u64 << Self::limb_bits()));
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for j in (0..Self::num_limbs()).rev() {
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let this_limb = vars.local_wires[Self::wire_ith_output_jth_limb(i, j)];
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let max_limb = 1 << Self::limb_bits();
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let mut product = builder.one_extension();
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for x in 0..max_limb {
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let x_target =
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builder.constant_extension(F::Extension::from_canonical_usize(x));
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let diff = builder.sub_extension(this_limb, x_target);
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product = builder.mul_extension(product, diff);
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}
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constraints.push(product);
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if j < midpoint {
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combined_low_limbs =
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builder.mul_add_extension(base, combined_low_limbs, this_limb);
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} else {
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combined_high_limbs =
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builder.mul_add_extension(base, combined_high_limbs, this_limb);
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}
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}
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constraints.push(builder.sub_extension(combined_low_limbs, output_low));
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constraints.push(builder.sub_extension(combined_high_limbs, output_high));
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}
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constraints
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}
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fn generators(
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&self,
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gate_index: usize,
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_local_constants: &[F],
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) -> Vec<Box<dyn WitnessGenerator<F>>> {
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(0..NUM_U32_ARITHMETIC_OPS)
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.map(|i| {
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let g: Box<dyn WitnessGenerator<F>> = Box::new(
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U32ArithmeticGenerator {
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gate_index,
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i,
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_phantom: PhantomData,
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}
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.adapter(),
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);
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g
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})
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.collect::<Vec<_>>()
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}
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fn num_wires(&self) -> usize {
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NUM_U32_ARITHMETIC_OPS * (5 + Self::num_limbs())
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}
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fn num_constants(&self) -> usize {
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0
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}
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fn degree(&self) -> usize {
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1 << Self::limb_bits()
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}
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fn num_constraints(&self) -> usize {
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NUM_U32_ARITHMETIC_OPS * (3 + Self::num_limbs())
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}
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}
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#[derive(Clone, Debug)]
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struct U32ArithmeticGenerator<F: RichField + Extendable<D>, const D: usize> {
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gate_index: usize,
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i: usize,
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_phantom: PhantomData<F>,
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}
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impl<F: RichField + Extendable<D>, const D: usize> SimpleGenerator<F>
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for U32ArithmeticGenerator<F, D>
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{
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fn dependencies(&self) -> Vec<Target> {
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let local_target = |input| Target::wire(self.gate_index, input);
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vec![
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local_target(U32ArithmeticGate::<F, D>::wire_ith_multiplicand_0(self.i)),
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local_target(U32ArithmeticGate::<F, D>::wire_ith_multiplicand_1(self.i)),
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local_target(U32ArithmeticGate::<F, D>::wire_ith_addend(self.i)),
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]
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}
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fn run_once(&self, witness: &PartitionWitness<F>, out_buffer: &mut GeneratedValues<F>) {
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let local_wire = |input| Wire {
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gate: self.gate_index,
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input,
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};
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let get_local_wire = |input| witness.get_wire(local_wire(input));
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let multiplicand_0 =
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get_local_wire(U32ArithmeticGate::<F, D>::wire_ith_multiplicand_0(self.i));
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let multiplicand_1 =
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get_local_wire(U32ArithmeticGate::<F, D>::wire_ith_multiplicand_1(self.i));
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let addend = get_local_wire(U32ArithmeticGate::<F, D>::wire_ith_addend(self.i));
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let output = multiplicand_0 * multiplicand_1 + addend;
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let mut output_u64 = output.to_canonical_u64();
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let output_high_u64 = output_u64 >> 32;
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let output_low_u64 = output_u64 & ((1 << 32) - 1);
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let output_high = F::from_canonical_u64(output_high_u64);
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let output_low = F::from_canonical_u64(output_low_u64);
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let output_high_wire =
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local_wire(U32ArithmeticGate::<F, D>::wire_ith_output_high_half(self.i));
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let output_low_wire =
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local_wire(U32ArithmeticGate::<F, D>::wire_ith_output_low_half(self.i));
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out_buffer.set_wire(output_high_wire, output_high);
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out_buffer.set_wire(output_low_wire, output_low);
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let num_limbs = U32ArithmeticGate::<F, D>::num_limbs();
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let limb_base = 1 << U32ArithmeticGate::<F, D>::limb_bits();
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let output_limbs_u64 = unfold((), move |_| {
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let ret = output_u64 % limb_base;
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output_u64 /= limb_base;
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Some(ret)
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})
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.take(num_limbs);
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let output_limbs_f = output_limbs_u64.map(F::from_canonical_u64);
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for (j, output_limb) in output_limbs_f.enumerate() {
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let wire = local_wire(U32ArithmeticGate::<F, D>::wire_ith_output_jth_limb(
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self.i, j,
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));
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out_buffer.set_wire(wire, output_limb);
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use std::marker::PhantomData;
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use anyhow::Result;
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use rand::Rng;
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use crate::field::extension_field::quartic::QuarticExtension;
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use crate::field::field_types::Field;
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use crate::field::goldilocks_field::GoldilocksField;
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use crate::gates::arithmetic_u32::{U32ArithmeticGate, NUM_U32_ARITHMETIC_OPS};
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use crate::gates::gate::Gate;
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use crate::gates::gate_testing::{test_eval_fns, test_low_degree};
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use crate::hash::hash_types::HashOut;
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use crate::plonk::vars::EvaluationVars;
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#[test]
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fn low_degree() {
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test_low_degree::<GoldilocksField, _, 4>(U32ArithmeticGate::<GoldilocksField, 4> {
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_phantom: PhantomData,
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})
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}
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#[test]
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fn eval_fns() -> Result<()> {
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test_eval_fns::<GoldilocksField, _, 4>(U32ArithmeticGate::<GoldilocksField, 4> {
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_phantom: PhantomData,
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})
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}
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#[test]
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fn test_gate_constraint() {
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type F = GoldilocksField;
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type FF = QuarticExtension<GoldilocksField>;
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const D: usize = 4;
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fn get_wires(
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multiplicands_0: Vec<u64>,
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multiplicands_1: Vec<u64>,
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addends: Vec<u64>,
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) -> Vec<FF> {
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let mut v0 = Vec::new();
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let mut v1 = Vec::new();
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let limb_bits = U32ArithmeticGate::<F, D>::limb_bits();
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let num_limbs = U32ArithmeticGate::<F, D>::num_limbs();
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let limb_base = 1 << limb_bits;
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for c in 0..NUM_U32_ARITHMETIC_OPS {
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let m0 = multiplicands_0[c];
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let m1 = multiplicands_1[c];
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let a = addends[c];
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let mut output = m0 * m1 + a;
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let output_low = output & ((1 << 32) - 1);
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let output_high = output >> 32;
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let mut output_limbs = Vec::with_capacity(num_limbs);
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for _i in 0..num_limbs {
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output_limbs.push(output % limb_base);
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output /= limb_base;
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}
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let mut output_limbs_f: Vec<_> = output_limbs
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.into_iter()
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.map(F::from_canonical_u64)
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.collect();
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v0.push(F::from_canonical_u64(m0));
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v0.push(F::from_canonical_u64(m1));
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v0.push(F::from_canonical_u64(a));
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v0.push(F::from_canonical_u64(output_low));
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v0.push(F::from_canonical_u64(output_high));
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v1.append(&mut output_limbs_f);
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}
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v0.iter()
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.chain(v1.iter())
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.map(|&x| x.into())
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.collect::<Vec<_>>()
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}
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let mut rng = rand::thread_rng();
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let multiplicands_0: Vec<_> = (0..NUM_U32_ARITHMETIC_OPS)
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.map(|_| rng.gen::<u32>() as u64)
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.collect();
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let multiplicands_1: Vec<_> = (0..NUM_U32_ARITHMETIC_OPS)
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.map(|_| rng.gen::<u32>() as u64)
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.collect();
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let addends: Vec<_> = (0..NUM_U32_ARITHMETIC_OPS)
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.map(|_| rng.gen::<u32>() as u64)
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.collect();
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let gate = U32ArithmeticGate::<F, D> {
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_phantom: PhantomData,
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};
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let vars = EvaluationVars {
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local_constants: &[],
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local_wires: &get_wires(multiplicands_0, multiplicands_1, addends),
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public_inputs_hash: &HashOut::rand(),
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};
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assert!(
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gate.eval_unfiltered(vars).iter().all(|x| x.is_zero()),
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"Gate constraints are not satisfied."
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);
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}
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}
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