sp1_recursion_core/chips/mem/

constant.rs

use core::borrow::Borrow;
use itertools::Itertools;
use p3_air::{Air, BaseAir, PairBuilder};
use p3_field::PrimeField32;
use p3_matrix::{dense::RowMajorMatrix, Matrix};
use sp1_core_machine::utils::pad_rows_fixed;
use sp1_derive::AlignedBorrow;
use sp1_stark::air::MachineAir;
use std::{borrow::BorrowMut, iter::zip, marker::PhantomData};

use crate::{builder::SP1RecursionAirBuilder, *};

use super::MemoryAccessCols;

pub const NUM_CONST_MEM_ENTRIES_PER_ROW: usize = 2;

#[derive(Default)]
pub struct MemoryChip<F> {
    _marker: PhantomData<F>,
}

pub const NUM_MEM_INIT_COLS: usize = core::mem::size_of::<MemoryCols<u8>>();

#[derive(AlignedBorrow, Debug, Clone, Copy)]
#[repr(C)]
pub struct MemoryCols<F: Copy> {
    // At least one column is required, otherwise a bunch of things break.
    _nothing: F,
}

pub const NUM_MEM_PREPROCESSED_INIT_COLS: usize =
    core::mem::size_of::<MemoryPreprocessedCols<u8>>();

#[derive(AlignedBorrow, Debug, Clone, Copy)]
#[repr(C)]
pub struct MemoryPreprocessedCols<F: Copy> {
    values_and_accesses: [(Block<F>, MemoryAccessCols<F>); NUM_CONST_MEM_ENTRIES_PER_ROW],
}
impl<F: Send + Sync> BaseAir<F> for MemoryChip<F> {
    fn width(&self) -> usize {
        NUM_MEM_INIT_COLS
    }
}

impl<F: PrimeField32> MachineAir<F> for MemoryChip<F> {
    type Record = crate::ExecutionRecord<F>;

    type Program = crate::RecursionProgram<F>;

    fn name(&self) -> String {
        "MemoryConst".to_string()
    }
    fn preprocessed_width(&self) -> usize {
        NUM_MEM_PREPROCESSED_INIT_COLS
    }

    fn generate_preprocessed_trace(&self, program: &Self::Program) -> Option<RowMajorMatrix<F>> {
        let mut rows = program
            .inner
            .iter()
            .filter_map(|instruction| match instruction {
                Instruction::Mem(MemInstr { addrs, vals, mult, kind }) => {
                    let mult = mult.to_owned();
                    let mult = match kind {
                        MemAccessKind::Read => -mult,
                        MemAccessKind::Write => mult,
                    };

                    Some((vals.inner, MemoryAccessCols { addr: addrs.inner, mult }))
                }
                _ => None,
            })
            .chunks(NUM_CONST_MEM_ENTRIES_PER_ROW)
            .into_iter()
            .map(|row_vs_as| {
                let mut row = [F::zero(); NUM_MEM_PREPROCESSED_INIT_COLS];
                let cols: &mut MemoryPreprocessedCols<_> = row.as_mut_slice().borrow_mut();
                for (cell, access) in zip(&mut cols.values_and_accesses, row_vs_as) {
                    *cell = access;
                }
                row
            })
            .collect::<Vec<_>>();

        // Pad the rows to the next power of two.
        pad_rows_fixed(
            &mut rows,
            || [F::zero(); NUM_MEM_PREPROCESSED_INIT_COLS],
            program.fixed_log2_rows(self),
        );

        // Convert the trace to a row major matrix.
        let trace = RowMajorMatrix::new(
            rows.into_iter().flatten().collect::<Vec<_>>(),
            NUM_MEM_PREPROCESSED_INIT_COLS,
        );

        Some(trace)
    }

    fn generate_dependencies(&self, _: &Self::Record, _: &mut Self::Record) {
        // This is a no-op.
    }

    fn generate_trace(&self, input: &Self::Record, _: &mut Self::Record) -> RowMajorMatrix<F> {
        // Match number of rows generated by the `.chunks` call in `generate_preprocessed_trace`.
        let num_rows = input
            .mem_const_count
            .checked_sub(1)
            .map(|x| x / NUM_CONST_MEM_ENTRIES_PER_ROW + 1)
            .unwrap_or_default();
        let mut rows =
            std::iter::repeat([F::zero(); NUM_MEM_INIT_COLS]).take(num_rows).collect::<Vec<_>>();

        // Pad the rows to the next power of two.
        pad_rows_fixed(&mut rows, || [F::zero(); NUM_MEM_INIT_COLS], input.fixed_log2_rows(self));

        // Convert the trace to a row major matrix.
        RowMajorMatrix::new(rows.into_iter().flatten().collect::<Vec<_>>(), NUM_MEM_INIT_COLS)
    }

    fn included(&self, _record: &Self::Record) -> bool {
        true
    }

    fn local_only(&self) -> bool {
        true
    }
}

impl<AB> Air<AB> for MemoryChip<AB::F>
where
    AB: SP1RecursionAirBuilder + PairBuilder,
{
    fn eval(&self, builder: &mut AB) {
        let prep = builder.preprocessed();
        let prep_local = prep.row_slice(0);
        let prep_local: &MemoryPreprocessedCols<AB::Var> = (*prep_local).borrow();

        for (value, access) in prep_local.values_and_accesses {
            builder.send_block(access.addr, value, access.mult);
        }
    }
}

#[cfg(test)]
mod tests {
    use machine::tests::test_recursion_linear_program;

    use super::*;

    use crate::runtime::instruction as instr;

    #[test]
    pub fn prove_basic_mem() {
        test_recursion_linear_program(vec![
            instr::mem(MemAccessKind::Write, 1, 1, 2),
            instr::mem(MemAccessKind::Read, 1, 1, 2),
        ]);
    }

    #[test]
    #[should_panic]
    pub fn basic_mem_bad_mult() {
        test_recursion_linear_program(vec![
            instr::mem(MemAccessKind::Write, 1, 1, 2),
            instr::mem(MemAccessKind::Read, 9, 1, 2),
        ]);
    }

    #[test]
    #[should_panic]
    pub fn basic_mem_bad_address() {
        test_recursion_linear_program(vec![
            instr::mem(MemAccessKind::Write, 1, 1, 2),
            instr::mem(MemAccessKind::Read, 1, 9, 2),
        ]);
    }

    #[test]
    #[should_panic]
    pub fn basic_mem_bad_value() {
        test_recursion_linear_program(vec![
            instr::mem(MemAccessKind::Write, 1, 1, 2),
            instr::mem(MemAccessKind::Read, 1, 1, 999),
        ]);
    }
}