simulate scenario from figure 4 in the Mysticeti paper

needed fix: call updateSkipped() when proposing a block

mysticeti/validator.nim

@@ -70,6 +70,12 @@ func updateCertified(validator: Validator, certificate: Block) =
       let stake = validator.committee.stake(certificate.author)
       proposal.certifyBy(certificate.id, stake)
 
+func addBlock(validator: Validator, signedBlock: SignedBlock) =
+  if round =? validator.rounds.latest.find(signedBlock.blck.round):
+    round.addProposal(signedBlock)
+    validator.updateSkipped(signedBlock.blck)
+    validator.updateCertified(signedBlock.blck)
+
 proc propose*(validator: Validator, transactions: seq[Transaction]): auto =
   type SignedBlock = blocks.SignedBlock[Validator.Signing, Validator.Hashing]
   let round = validator.rounds.latest
@@ -93,8 +99,7 @@ proc propose*(validator: Validator, transactions: seq[Transaction]): auto =
     transactions = transactions
   )
   let signedBlock = validator.identity.sign(blck)
-  round.addProposal(signedBlock)
-  validator.updateCertified(blck)
+  validator.addBlock(signedBlock)
   success signedBlock
 
 func check*(validator: Validator, signed: SignedBlock): auto =
@@ -134,10 +139,7 @@ func check*(validator: Validator, signed: SignedBlock): auto =
   BlockCheck.correct(signed)
 
 func receive*(validator: Validator, correct: CorrectBlock) =
-  if round =? validator.rounds.latest.find(correct.blck.round):
-    round.addProposal(correct.signedBlock)
-    validator.updateSkipped(correct.blck)
-    validator.updateCertified(correct.blck)
+  validator.addBlock(correct.signedBlock)
 
 func getBlock*(validator: Validator, id: BlockId): auto =
   validator.rounds.latest.find(id)

tests/mysticeti/scenarios.nim

@@ -0,0 +1,52 @@
+import ./basics
+import ./simulator
+
+proc scenarioFigure4*(simulator: NetworkSimulator): ?!seq[seq[SignedBlock]] =
+  # replays scenario from Figure 4 in the Mysticeti paper
+  # https://arxiv.org/pdf/2310.14821v4
+  # note: round robin is not applied correctly in the figure from
+  # the Mysticeti paper, so this simulation uses different proposer
+  # labels from the fourth round
+  var proposals: seq[seq[SignedBlock]]
+  proposals.add(? simulator.exchangeProposals {
+    0: @[0, 1, 2, 3],
+    1: @[0, 1],
+    2: @[0, 2, 3],
+    3: @[1, 2, 3]
+  })
+  simulator.nextRound()
+  proposals.add(? simulator.exchangeProposals {
+    0: @[0, 1, 3],
+    1: @[0, 1, 3],
+    2: @[0, 3],
+    3: @[1, 3]
+  })
+  simulator.nextRound()
+  proposals.add(? simulator.exchangeProposals {
+    0: @[2, 3, 0, 1],
+    1: @[2, 3, 0, 1],
+
+    3: @[2, 3, 0, 1]
+  })
+  simulator.nextRound()
+  proposals.add(? simulator.exchangeProposals {
+    2: @[2, 3, 0, 1],
+    3: @[3],
+    0: @[2, 3, 0, 1],
+    1: @[2, 3, 0, 1]
+  })
+  simulator.nextRound()
+  proposals.add(? simulator.exchangeProposals {
+    2: @[],
+    3: @[2, 3, 0],
+    0: @[2, 3, 0],
+    1: @[2, 3, 0]
+  })
+  simulator.nextRound()
+  proposals.add(? simulator.exchangeProposals {
+    2: @[2, 3, 0],
+    3: @[2, 3, 0],
+    0: @[2, 3, 0]
+
+  })
+  success proposals

tests/mysticeti/simulator.nim

@@ -2,9 +2,9 @@ import ./basics
 import mysticeti
 import mysticeti/blocks
 
-type Validator = mysticeti.Validator[MockSigning, MockHashing]
-type Identity = mysticeti.Identity[MockSigning]
-type SignedBlock = blocks.SignedBlock[MockSigning, MockHashing]
+type Validator* = mysticeti.Validator[MockSigning, MockHashing]
+type Identity* = mysticeti.Identity[MockSigning]
+type SignedBlock* = blocks.SignedBlock[MockSigning, MockHashing]
 
 type NetworkSimulator* = object
   identities: seq[Identity]

tests/mysticeti/validator/testMultiple.nim

@@ -1,5 +1,6 @@
 import ../basics
 import ../simulator
+import ../scenarios
 import mysticeti
 import mysticeti/blocks
 import mysticeti/hashing
@@ -269,70 +270,11 @@ suite "Multiple Validators":
     check toSeq(simulator.validators[0].committed()) == second
 
   test "commits blocks using the indirect decision rule":
-    # first round: proposals
-    let proposals = !simulator.exchangeProposals {
-      0: @[0, 1, 2, 3],
-      1: @[0, 1],
-      2: @[0, 2, 3],
-      3: @[1, 2, 3]
-    }
-    # second round: voting
-    simulator.nextRound()
-    discard !simulator.exchangeProposals {
-      0: @[0, 1, 3],
-      1: @[0, 1, 3],
-      2: @[0, 3],
-      3: @[1, 3]
-    }
-    # third round: certifying
-    simulator.nextRound()
-    discard !simulator.exchangeProposals {
-      0: @[0, 1, 2, 3],
-      1: @[0, 1, 2, 3],
-      3: @[0, 1, 2, 3]
-    }
-    # fourth round: anchor
-    simulator.nextRound()
-    discard !simulator.exchangeProposals()
-    # fifth round: voting on anchor
-    simulator.nextRound()
-    discard !simulator.exchangeProposals()
-    # sixth round: certifying anchor
-    simulator.nextRound()
-    discard !simulator.exchangeProposals()
-    check toSeq(simulator.validators[0].committed()).contains(proposals[3].blck)
+    let proposals = !scenarioFigure4(simulator)
+    let committed = toSeq(simulator.validators[0].committed())
+    check committed.contains(proposals[0][3].blck)
 
   test "skips blocks using the indirect decision rule":
-    # Modelled after Figure 3f from the Mysticeti paper
-    # first round: proposals
-    let proposals = !simulator.exchangeProposals {
-      0: @[0, 1, 2, 3],
-      1: @[0, 1],
-      2: @[0, 2, 3],
-      3: @[1, 2, 3]
-    }
-    # second round: voting
-    simulator.nextRound()
-    discard !simulator.exchangeProposals {
-      0: @[0, 1, 3],
-      1: @[0, 1, 3],
-      2: @[0, 3],
-      3: @[1, 3]
-    }
-    # third round: certifying
-    simulator.nextRound()
-    discard !simulator.exchangeProposals {
-      0: @[0, 1, 2, 3],
-      1: @[0, 1, 2, 3],
-      3: @[0, 1, 2, 3]
-    }
-    # fourth round: anchor
-    simulator.nextRound()
-    discard !simulator.exchangeProposals()
-    # fifth round: voting on anchor
-    simulator.nextRound()
-    discard !simulator.exchangeProposals()
-    # sixth round: certifying anchor
-    simulator.nextRound()
-    discard !simulator.exchangeProposals()
-    check not toSeq(simulator.validators[0].committed()).contains(proposals[1].blck)
+    let proposals = !scenarioFigure4(simulator)
+    let committed = toSeq(simulator.validators[0].committed())
+    check not committed.contains(proposals[0][1].blck)