openvm_stark_backend/prover/
coordinator.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
use std::{iter, marker::PhantomData};

use itertools::{izip, Itertools};
use p3_challenger::CanObserve;
use p3_field::FieldAlgebra;
use p3_util::log2_strict_usize;
use tracing::{info, instrument};

use super::{
    hal::{ProverBackend, ProverDevice},
    types::{DeviceMultiStarkProvingKey, HalProof, ProvingContext},
    Prover,
};
#[cfg(feature = "bench-metrics")]
use crate::prover::metrics::trace_metrics;
use crate::{
    config::{Com, StarkGenericConfig, Val},
    keygen::view::MultiStarkVerifyingKeyView,
    proof::{AirProofData, Commitments},
    prover::{
        hal::MatrixDimensions,
        types::{PairView, SingleCommitPreimage},
    },
    utils::metrics_span,
};

/// Host-to-device coordinator for full prover implementation.
///
/// The generics are:
/// - `SC`: Stark configuration for proving key (from host)
/// - `PB`: Prover backend types
/// - `PD`: Prover device methods
pub struct Coordinator<SC: StarkGenericConfig, PB, PD> {
    pub backend: PB,
    pub device: PD,
    challenger: SC::Challenger,
    phantom: PhantomData<(SC, PB)>,
}

impl<SC: StarkGenericConfig, PB, PD> Coordinator<SC, PB, PD> {
    pub fn new(backend: PB, device: PD, challenger: SC::Challenger) -> Self {
        Self {
            backend,
            device,
            challenger,
            phantom: PhantomData,
        }
    }
}

impl<SC, PB, PD> Prover for Coordinator<SC, PB, PD>
where
    SC: StarkGenericConfig,
    PB: ProverBackend<
        Val = Val<SC>,
        Challenge = SC::Challenge,
        Commitment = Com<SC>,
        Challenger = SC::Challenger,
    >,
    PD: ProverDevice<PB>,
{
    type Proof = HalProof<PB>;
    type ProvingKeyView<'a>
        = &'a DeviceMultiStarkProvingKey<'a, PB>
    where
        Self: 'a;

    type ProvingContext<'a>
        = ProvingContext<'a, PB>
    where
        Self: 'a;

    /// Specialized prove for InteractiveAirs.
    /// Handles trace generation of the permutation traces.
    /// Assumes the main traces have been generated and committed already.
    ///
    /// The [DeviceMultiStarkProvingKey] should already be filtered to only include the relevant AIR's proving keys.
    #[instrument(name = "Coordinator::prove", level = "info", skip_all)]
    fn prove<'a>(
        &'a mut self,
        mpk: Self::ProvingKeyView<'a>,
        ctx: Self::ProvingContext<'a>,
    ) -> Self::Proof {
        #[cfg(feature = "bench-metrics")]
        let start = std::time::Instant::now();
        assert!(mpk.validate(&ctx), "Invalid proof input");
        self.challenger.observe(mpk.vk_pre_hash.clone());

        let num_air = ctx.per_air.len();
        info!(num_air);
        #[allow(clippy::type_complexity)]
        let (cached_commits_per_air, cached_views_per_air, common_main_per_air, pvs_per_air): (
            Vec<Vec<PB::Commitment>>,
            Vec<Vec<SingleCommitPreimage<&'a PB::Matrix, &'a PB::PcsData>>>,
            Vec<Option<PB::Matrix>>,
            Vec<Vec<PB::Val>>,
        ) = ctx
            .into_iter()
            .map(|(_, ctx)| {
                let (cached_commits, cached_views): (Vec<_>, Vec<_>) =
                    ctx.cached_mains.into_iter().unzip();
                (
                    cached_commits,
                    cached_views,
                    ctx.common_main,
                    ctx.public_values,
                )
            })
            .multiunzip();

        // ==================== All trace commitments that do not require challenges ====================
        // Commit all common main traces in a commitment. Traces inside are ordered by AIR id.
        let (common_main_traces, (common_main_commit, common_main_pcs_data)) =
            metrics_span("main_trace_commit_time_ms", || {
                let traces = common_main_per_air.into_iter().flatten().collect_vec();
                let prover_data = self.device.commit(&traces);
                (traces, prover_data)
            });

        // Commitments order:
        // - for each air:
        //   - for each cached main trace
        //     - 1 commitment
        // - 1 commitment of all common main traces
        let main_trace_commitments: Vec<PB::Commitment> = cached_commits_per_air
            .iter()
            .flatten()
            .chain(iter::once(&common_main_commit))
            .cloned()
            .collect();

        // All commitments that don't require challenges have been made, so we collect them into trace views:
        let mut common_main_idx = 0;
        let mut log_trace_height_per_air: Vec<u8> = Vec::with_capacity(num_air);
        let mut pair_trace_view_per_air = Vec::with_capacity(num_air);
        for (pk, cached_views, pvs) in izip!(&mpk.per_air, &cached_views_per_air, &pvs_per_air) {
            let mut main_trace_views: Vec<&PB::Matrix> =
                cached_views.iter().map(|view| view.trace).collect_vec();
            if pk.vk.has_common_main() {
                main_trace_views.push(&common_main_traces[common_main_idx]);
                common_main_idx += 1;
            }
            let trace_height = main_trace_views.first().expect("no main trace").height();
            let log_trace_height: u8 = log2_strict_usize(trace_height).try_into().unwrap();
            let pair_trace_view = PairView {
                log_trace_height,
                preprocessed: pk.preprocessed_data.as_ref().map(|d| &d.trace),
                partitioned_main: main_trace_views,
                public_values: pvs.to_vec(),
            };
            log_trace_height_per_air.push(log_trace_height);
            pair_trace_view_per_air.push(pair_trace_view);
        }
        #[cfg(feature = "bench-metrics")]
        trace_metrics(mpk, &log_trace_height_per_air).emit();

        // ============ Challenger observations before additional RAP phases =============
        // Observe public values:
        for pvs in &pvs_per_air {
            self.challenger.observe_slice(pvs);
        }

        // Observes preprocessed and main commitments:
        let mvk = mpk.vk_view();
        let preprocessed_commits = mvk.flattened_preprocessed_commits();
        self.challenger.observe_slice(&preprocessed_commits);
        self.challenger.observe_slice(&main_trace_commitments);
        // Observe trace domain size per air:
        self.challenger.observe_slice(
            &log_trace_height_per_air
                .iter()
                .copied()
                .map(Val::<SC>::from_canonical_u8)
                .collect_vec(),
        );

        // ==================== Partially prove all RAP phases that require challenges ====================
        let (rap_partial_proof, prover_data_after) =
            self.device
                .partially_prove(&mut self.challenger, mpk, pair_trace_view_per_air);
        // Challenger observes additional commitments if any exist:
        for (commit, _) in &prover_data_after.committed_pcs_data_per_phase {
            self.challenger.observe(commit.clone());
        }

        // Collect exposed_values_per_air for the proof:
        // - transpose per_phase, per_air -> per_air, per_phase
        let exposed_values_per_air = (0..num_air)
            .map(|i| {
                let mut values = prover_data_after
                    .rap_views_per_phase
                    .iter()
                    .map(|per_air| {
                        per_air
                            .get(i)
                            .and_then(|v| v.inner.map(|_| v.exposed_values.clone()))
                    })
                    .collect_vec();
                // Prune Nones
                while let Some(last) = values.last() {
                    if last.is_none() {
                        values.pop();
                    } else {
                        break;
                    }
                }
                values
                    .into_iter()
                    .map(|v| v.unwrap_or_default())
                    .collect_vec()
            })
            .collect_vec();

        // ==================== Quotient polynomial computation and commitment, if any ====================
        // Note[jpw]: Currently we always call this step, we could add a flag to skip it for protocols that
        // do not require quotient poly.
        let (quotient_commit, quotient_data) = self.device.eval_and_commit_quotient(
            &mut self.challenger,
            &mpk.per_air,
            &pvs_per_air,
            &cached_views_per_air,
            &common_main_pcs_data,
            &prover_data_after,
        );
        // Observe quotient commitment
        self.challenger.observe(quotient_commit.clone());

        let (commitments_after, pcs_data_after): (Vec<_>, Vec<_>) = prover_data_after
            .committed_pcs_data_per_phase
            .into_iter()
            .unzip();
        // ==================== Polynomial Opening Proofs ====================
        let opening = metrics_span("pcs_opening_time_ms", || {
            let mut quotient_degrees = Vec::with_capacity(mpk.per_air.len());
            let mut preprocessed = Vec::new();

            for pk in &mpk.per_air {
                quotient_degrees.push(pk.vk.quotient_degree);
                if let Some(data) = pk.preprocessed_data.as_ref().map(|d| &d.data) {
                    preprocessed.push(data);
                }
            }

            let main = cached_views_per_air
                .into_iter()
                .flatten()
                .map(|cv| cv.data)
                .chain(iter::once(&common_main_pcs_data))
                .collect();
            self.device.open(
                &mut self.challenger,
                preprocessed,
                main,
                pcs_data_after,
                quotient_data,
                &quotient_degrees,
            )
        });

        // ==================== Collect data into proof ====================
        // Collect the commitments
        let commitments = Commitments {
            main_trace: main_trace_commitments,
            after_challenge: commitments_after,
            quotient: quotient_commit,
        };
        let proof = HalProof {
            commitments,
            opening,
            per_air: izip!(
                &mpk.air_ids,
                log_trace_height_per_air,
                exposed_values_per_air,
                pvs_per_air
            )
            .map(
                |(&air_id, log_height, exposed_values, public_values)| AirProofData {
                    air_id,
                    degree: 1 << log_height,
                    public_values,
                    exposed_values_after_challenge: exposed_values,
                },
            )
            .collect(),
            rap_partial_proof,
        };

        #[cfg(feature = "bench-metrics")]
        ::metrics::gauge!("stark_prove_excluding_trace_time_ms")
            .set(start.elapsed().as_millis() as f64);

        proof
    }
}

impl<'a, PB: ProverBackend> DeviceMultiStarkProvingKey<'a, PB> {
    pub(crate) fn validate(&self, ctx: &ProvingContext<PB>) -> bool {
        ctx.per_air.len() == self.air_ids.len()
            && ctx
                .per_air
                .iter()
                .zip(&self.air_ids)
                .all(|((id1, _), id2)| id1 == id2)
            && ctx.per_air.iter().tuple_windows().all(|(a, b)| a.0 < b.0)
    }

    pub(crate) fn vk_view(&'a self) -> MultiStarkVerifyingKeyView<'a, PB::Val, PB::Commitment> {
        MultiStarkVerifyingKeyView::new(
            self.per_air.iter().map(|pk| pk.vk).collect(),
            &self.trace_height_constraints,
            self.vk_pre_hash.clone(),
        )
    }
}