sp1_core_machine/operations/
add5.rs

1use slop_algebra::{AbstractField, Field};
2use sp1_derive::AlignedBorrow;
3
4use sp1_core_executor::events::ByteRecord;
5use sp1_hypercube::air::SP1AirBuilder;
6use sp1_primitives::consts::u32_to_u16_limbs;
7
8use crate::{air::WordAirBuilder, utils::u32_to_half_word};
9
10/// A set of columns needed to compute the sum of five u32s as u32.
11#[derive(AlignedBorrow, Default, Debug, Clone, Copy)]
12#[repr(C)]
13pub struct Add5Operation<T> {
14    /// The result of `a + b + c + d + e`.
15    pub value: [T; 2],
16}
17
18impl<F: Field> Add5Operation<F> {
19    #[allow(clippy::too_many_arguments)]
20    pub fn populate(
21        &mut self,
22        record: &mut impl ByteRecord,
23        a_u32: u32,
24        b_u32: u32,
25        c_u32: u32,
26        d_u32: u32,
27        e_u32: u32,
28    ) -> u32 {
29        let expected =
30            a_u32.wrapping_add(b_u32).wrapping_add(c_u32).wrapping_add(d_u32).wrapping_add(e_u32);
31        let expected_limbs = u32_to_u16_limbs(expected);
32        self.value = u32_to_half_word(expected);
33        let a = u32_to_u16_limbs(a_u32);
34        let b = u32_to_u16_limbs(b_u32);
35        let c = u32_to_u16_limbs(c_u32);
36        let d = u32_to_u16_limbs(d_u32);
37        let e = u32_to_u16_limbs(e_u32);
38        let base = 1u32 << 16;
39        let mut carry = 0;
40        let mut carry_limbs = [0u8; 2];
41        for i in 0..2 {
42            carry = ((a[i] as u32)
43                + (b[i] as u32)
44                + (c[i] as u32)
45                + (d[i] as u32)
46                + (e[i] as u32)
47                + carry
48                - expected_limbs[i] as u32)
49                / base;
50            carry_limbs[i] = carry as u8;
51        }
52
53        // Range check.
54        record.add_u16_range_checks(&expected_limbs);
55        record.add_u8_range_checks(&carry_limbs);
56        expected
57    }
58
59    /// Evaluate the add5 operation.
60    /// Assumes that the five words are valid u32s of two u16 limbs.
61    /// Constrains that `is_real` is boolean.
62    /// If `is_real` is true, the `value` is constrained to a valid u32 representing the sum.
63    pub fn eval<AB: SP1AirBuilder>(
64        builder: &mut AB,
65        words: &[[AB::Expr; 2]; 5],
66        is_real: AB::Var,
67        cols: Add5Operation<AB::Var>,
68    ) {
69        builder.assert_bool(is_real);
70
71        let base = AB::F::from_canonical_u32(1 << 16);
72        let mut carry_limbs = [AB::Expr::zero(), AB::Expr::zero()];
73        let mut carry = AB::Expr::zero(); // Initialize carry to zero
74
75        // The set of constraints are
76        //  - carry is initialized to zero
77        //  - 2^16 * carry_next + value[i] = sum(word[i]) + carry
78        //  - 0 <= carry < 2^8
79        //  - 0 <= value[i] < 2^16
80        // Since the carries are bounded by 2^8, no SP1Field overflows are possible.
81        // The maximum carry possible is less than 2^8, so the circuit is complete.
82        for i in 0..2 {
83            carry = (words[0][i].clone()
84                + words[1][i].clone()
85                + words[2][i].clone()
86                + words[3][i].clone()
87                + words[4][i].clone()
88                - cols.value[i]
89                + carry.clone())
90                * base.inverse();
91            carry_limbs[i] = carry.clone();
92        }
93        // Range check each limb.
94        builder.slice_range_check_u16(&cols.value, is_real);
95        builder.slice_range_check_u8(&carry_limbs, is_real);
96    }
97}
sp1_core_machine/operations/add5.rs

sp1_core_machine/operations/
add5.rs
