Networksim additions + fix agents and normal_distribution types

beacon_chain/fork_choice_rule/distributions.nim

@@ -12,11 +12,14 @@
 
 import math, random
 
-proc normal_distribution*(mean = 0.0, std = 1.0): int =
+proc normal_distribution*(mean = 0, std = 1): int =
   ## Return an integer sampled from a normal distribution (gaussian)
   ## ⚠ This is not thread-safe
   # Implementation via the Box-Muller method
   # See https://en.wikipedia.org/wiki/Box–Muller_transform
+  let
+    mean = mean.float
+    std = std.float
 
   var
     z1 {.global.}: float
@@ -46,8 +49,8 @@ when isMainModule:
     abs(y_true - y)/abs(y_true)
 
   let
-    mu = 1000f
-    sigma = 12f
+    mu = 1000
+    sigma = 12
     a = newSeqWith(10000000, normal_distribution(mean = mu, std = sigma))
 
   var statistics: RunningStat
@@ -61,13 +64,13 @@ when isMainModule:
     echo &"{stat:<20} {value:>9.4f} | Expected: {expected:>9.4f}"
 
   echo &"Statistics on {a.len} samples"
-  report "Mean: ", statistics.mean, mu
-  report "Standard deviation: ", statistics.standardDeviationS, sigma
+  report "Mean: ", statistics.mean, mu.float
+  report "Standard deviation: ", statistics.standardDeviationS, sigma.float
 
   # Absolute error
-  doAssert absolute_error(mu, statistics.mean) < 0.6
-  doAssert absolute_error(sigma, statistics.standardDeviationS) < 0.01
+  doAssert absolute_error(mu.float, statistics.mean) < 0.6
+  doAssert absolute_error(sigma.float, statistics.standardDeviationS) < 0.01
 
   # Relative error
-  doAssert relative_error(mu, statistics.mean) < 0.01
-  doAssert relative_error(sigma, statistics.standardDeviationS) < 0.01
+  doAssert relative_error(mu.float, statistics.mean) < 0.01
+  doAssert relative_error(sigma.float, statistics.standardDeviationS) < 0.01

beacon_chain/fork_choice_rule/fork_choice_types.nim

@@ -104,7 +104,7 @@ func hash*(x: Duration): Hash =
 
 type
   NetworkSimulator* = ref object
-    agents*: seq[int]
+    agents*: seq[Node]
     latency_distribution_sample*: proc (): Duration
     time*: Duration
     objqueue*: TableRef[Duration, seq[(Node, BlockOrSig)]]

beacon_chain/fork_choice_rule/networksim.nim

@@ -10,8 +10,32 @@
 # Part of Casper+Sharding chain v2.1: https://notes.ethereum.org/SCIg8AH5SA-O4C1G1LYZHQ#
 
 import
-  tables, times,
-  ./fork_choice_types
+  tables, times, sugar, random,
+  ./fork_choice_types, ./distributions
+
+proc initNetworkSimulator*(latency: int): NetworkSimulator =
+  result.latency_distribution_sample = () => initDuration(
+    seconds = max(
+      0,
+      normal_distribution(latency, latency * 2 div 5)
+    )
+  )
+  result.reliability = 0.9
+  result.objqueue = newTable[Duration, seq[(Node, BlockOrSig)]]()
+  result.peers = newTable[int, seq[Node]]()
+
+proc generate_peers*(self: NetworkSimulator, num_peers = 5) =
+  self.peers.clear()
+  var p: seq[Node]
+  for a in self.agents:
+    p.setLen(0) # reset without involving GC/realloc
+    while p.len <= num_peers div 2:
+      p.add self.agents.rand()
+      if p[^1] == a:
+        discard p.pop()
+    self.peers[a.id].add p
+    for peer in p:
+      self.peers[peer.id].add a
 
 func broadcast*(self: NetworkSimulator, sender: Node, obj: BlockOrSig) =
   for p in self.peers[sender.id]: