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This commit is contained in:
Nicholas Ward 2021-10-14 13:41:51 -07:00
parent 18567e570b
commit cc48abff94
1 changed files with 14 additions and 10 deletions
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24
src/gadgets/arithmetic_u32.rs
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@ -3,6 +3,7 @@ use std::marker::PhantomData;
use crate::field::extension_field::Extendable;
use crate::field::field_types::RichField;
use crate::gates::arithmetic_u32::{U32ArithmeticGate, NUM_U32_ARITHMETIC_OPS};
use crate::gates::subtraction_u32::U32SubtractionGate;
use crate::iop::target::Target;
use crate::plonk::circuit_builder::CircuitBuilder;
@ -91,7 +92,7 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
self.mul_add_u32(a, b, zero)
}
// Returns x * y + z.
// Returns x - y - borrow, as a pair (result, borrow), where borrow is 0 or 1 depending on whether borrowing from the next digit is required (iff y + borrow > x).
pub fn sub_u32(
&mut self,
x: U32Target,
@ -103,31 +104,34 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
self.connect(
Target::wire(
gate_index,
U32ArithmeticGate::<F, D>::wire_ith_multiplicand_0(copy),
U32SubtractionGate::<F, D>::wire_ith_input_x(copy),
),
x.0,
);
self.connect(
Target::wire(
gate_index,
U32ArithmeticGate::<F, D>::wire_ith_multiplicand_1(copy),
U32SubtractionGate::<F, D>::wire_ith_input_y(copy),
),
y.0,
);
self.connect(
Target::wire(gate_index, U32ArithmeticGate::<F, D>::wire_ith_addend(copy)),
z.0,
Target::wire(
gate_index,
U32SubtractionGate::<F, D>::wire_ith_input_borrow(copy),
),
borrow.0,
);
let output_low = U32Target(Target::wire(
let output_result = U32Target(Target::wire(
gate_index,
U32ArithmeticGate::<F, D>::wire_ith_output_low_half(copy),
U32SubtractionGate::<F, D>::wire_ith_output_result(copy),
));
let output_high = U32Target(Target::wire(
let output_borrow = U32Target(Target::wire(
gate_index,
U32ArithmeticGate::<F, D>::wire_ith_output_high_half(copy),
U32SubtractionGate::<F, D>::wire_ith_output_borrow(copy),
));
(output_low, output_high)
(output_result, output_borrow)
}
}