Author: shuangcrypto.com

following the first post

got two tasks:

• generate trace from pil to stwo
• implement FrameworkEval trait, which is used by stwo to define constraint, to PowdrCircuit

let’s talk about generate trace first.

in stwo, the trace is in this format as showed in last post

ColumnVec<CircleEvaluation<SimdBackend, BaseField, BitReversedOrder>>

how powdr …

stwo:

cargo run -r --features stwo pil test_data/pil/fibonacci.pil -o output -f --field m31 --prove-with stwo

prove with plonky3

cargo run pil test_data/pil/fibonacci.pil -o output -f --field bb --prove-with plonky3

hello world example

cargo run pil test_data/asm/book/hello_world.asm --inputs 0 -o output --field m31 --prove-with plonky3 -f

…

in Powdr, the proving function of Plonky3 is in function prove_with_key, in stark.rs

you can see the inputs for prove_with_key function has “air”, this is what used to define constraints, powdr gives “&circuit” to it, and it is a powdrcircuit, probably powdrcircuit applies the trait of AIR

so at this …

it is about this example in stwo

two parameters:

FIB_SEQUENCE_LENGTH specifies the rounds of fibo sequence

LOG_N_INSTANCES as stwo use SIMD, data parallel data struct, this number specify how many instances of fibo sequences are proved at the same time. The data are packed in LOG_N_LANES chunks, which is 16 …

following note1

packed31 is a vector of length 16

try to understand how the trace is generated

the bottom lines actually transfer the M31 values into circleDomain

from start:

N is log N instances

this code is to initialise the witness columns, later use to store the witness.

this code …

Powdr side

backend trait in powdr

• verify
• prove
• export_verification_key

how plonky3 implemented? this is in mod.rs

in mod.rs the backend trait is implemented for plonky3prover, in the prove function, it calls prove in stark.rs, where plonky3prover is implemented

so this prove function in stark.rs should be simliarly implemented in prover.rs …

hello world example

make the powdr-rs compiler up to date, pull the lasted changes in the repo, in powdr folder do the following:

cargo install --path ./cli-rs

use powdr-rs to compile rust file

powdr-rs compile riscv/tests/riscv_data/std_hello_world -o output

this will generate asm in output, then use pil to compile the …