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feat(avm): Equivalence check between Main trace and Mem trace #5032

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Mar 11, 2024
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22 changes: 17 additions & 5 deletions barretenberg/cpp/pil/avm/avm_main.pil
Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,7 @@ namespace avm_main(256);
pol commit mem_op_a;
pol commit mem_op_b;
pol commit mem_op_c;

// Read-write flag per intermediate register: Read = 0, Write = 1
pol commit rwa;
pol commit rwb;
Expand Down Expand Up @@ -104,7 +104,7 @@ namespace avm_main(256);
rwa * (1 - rwa) = 0;
rwb * (1 - rwb) = 0;
rwc * (1 - rwc) = 0;

// TODO: Constrain rwa, rwb, rwc to u32 type and 0 <= in_tag <= 6

// Relation for division over the finite field
Expand Down Expand Up @@ -189,7 +189,7 @@ namespace avm_main(256);
// TODO: we want to set an initial number for the reserved memory of the jump pointer

// Inter-table Constraints

#[equiv_tag_err]
avm_mem.m_tag_err {avm_mem.m_clk} in tag_err {clk};

Expand All @@ -207,5 +207,17 @@ namespace avm_main(256);
avm_alu.alu_op_add, avm_alu.alu_op_sub, avm_alu.alu_op_mul, avm_alu.alu_op_eq,
avm_alu.alu_op_not, avm_alu.alu_in_tag};

// TODO: Map memory trace with intermediate register values whenever there is no tag error, sthg like:
// mem_op_a * (1 - tag_err) {mem_idx_a, clk, ia, rwa} IS m_sub_clk == 0 && 1 - m_tag_err {m_addr, m_clk, m_val, m_rw}
#[equiv_main_mem_a]
mem_op_a {clk, mem_idx_a, ia, rwa, in_tag}
is
avm_mem.m_op_a {avm_mem.m_clk, avm_mem.m_addr, avm_mem.m_val, avm_mem.m_rw, avm_mem.m_in_tag};

#[equiv_main_mem_b]
mem_op_b {clk, mem_idx_b, ib, rwb, in_tag}
is
avm_mem.m_op_b {avm_mem.m_clk, avm_mem.m_addr, avm_mem.m_val, avm_mem.m_rw, avm_mem.m_in_tag};

#[equiv_main_mem_c]
mem_op_c {clk, mem_idx_c, ic, rwc, in_tag}
is
avm_mem.m_op_c {avm_mem.m_clk, avm_mem.m_addr, avm_mem.m_val, avm_mem.m_rw, avm_mem.m_in_tag};
24 changes: 16 additions & 8 deletions barretenberg/cpp/pil/avm/avm_mem.pil
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,11 @@ namespace avm_mem(256);

pol commit m_in_tag; // Instruction memory tag ("foreign key" pointing to avm_main.in_tag)

// Indicator of the intermediate register pertaining to the memory operation (foreign key to avm_main.mem_op_XXX)
pol commit m_op_a;
pol commit m_op_b;
pol commit m_op_c;

// Error columns
pol commit m_tag_err; // Boolean (1 if m_in_tag != m_tag is detected)

Expand All @@ -26,10 +31,20 @@ namespace avm_mem(256);
m_last * (1 - m_last) = 0;
m_rw * (1 - m_rw) = 0;
m_tag_err * (1 - m_tag_err) = 0;
m_op_a * (1 - m_op_a) = 0;
m_op_b * (1 - m_op_b) = 0;
m_op_c * (1 - m_op_c) = 0;

// TODO: m_addr is u32 and 0 <= m_tag <= 6
// (m_in_tag will be constrained through inclusion check to main trace)

// sub_clk derivation
m_sub_clk = 3 * m_rw + m_op_b + 2 * m_op_c;

// Maximum one memory operation enabled per row
pol M_OP_SUM = m_op_a + m_op_b + m_op_c;
M_OP_SUM * (M_OP_SUM - 1) = 0;

// Remark: m_lastAccess == 1 on first row and therefore any relation with the
// multiplicative term (1 - m_lastAccess) implicitly includes (1 - avm_main.first)
// Similarly, this includes (1 - m_last) as well.
Expand Down Expand Up @@ -96,11 +111,4 @@ namespace avm_mem(256);

// Correctness of two above checks MEM_IN_TAG_CONSISTENCY_1/2:
// m_in_tag == m_tag ==> m_tag_err == 0 (first relation)
// m_tag_err == 0 ==> m_one_min_inv == 0 by second relation. First relation ==> m_in_tag - m_tag == 0

// TODO: when introducing load/store as sub-operations, we will have to add consistency of intermediate
// register values ia, ib, ic

// Inter-table Constraints

// TODO: {m_clk, m_in_tag} IN {avm_main.clk, avm_main.in_tag}
// m_tag_err == 0 ==> m_one_min_inv == 0 by second relation. First relation ==> m_in_tag - m_tag == 0
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