Introduce changeable magnitude weight factors for polling

src/gridcoin/voting/result.cpp

@@ -2,6 +2,7 @@
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or https://opensource.org/licenses/mit-license.php.
 
+#include "gridcoin/protocol.h"
 #include "main.h"
 #include "gridcoin/beacon.h"
 #include "gridcoin/quorum.h"
@@ -787,7 +788,7 @@ class VoteCounter
     //! \param supply     The total network money supply as of the latest
     //! block in the poll window in units of 1/100000000 GRC.
     //!
-    void EnableMagnitudeWeight(SuperblockPtr superblock, const uint64_t supply)
+    void EnableMagnitudeWeight(SuperblockPtr superblock, const uint64_t supply, const Fraction magnitude_weight_factor)
     {
         const uint64_t total_mag = superblock->m_cpids.TotalMagnitude();
 
@@ -796,7 +797,9 @@ class VoteCounter
         }
 
         // Use integer arithmetic to avoid floating-point discrepancies:
-        m_magnitude_factor = supply / total_mag * 100 / 567;
+        m_magnitude_factor = supply / total_mag
+                             * (uint64_t) magnitude_weight_factor.GetNumerator()
+                             / (uint64_t) magnitude_weight_factor.GetDenominator();
         m_resolver.SetSuperblock(std::move(superblock));
     }
 
@@ -1133,6 +1136,30 @@ CAmount ResolveMoneySupplyForPoll(const Poll& poll)
 
     return pindex->nMoneySupply;
 }
+
+//!
+//! \brief Fetch the applicable magnitude factor for the poll. This is the magnitude factor of the last entry in the
+//! protocol registry database that has a timestamp at or before the poll start timestamp.
+//!
+//! \param poll Poll for which to fetch the Magnitude Weight Factor.
+//! \return Fraction Magnitude factor expressed as a Fraction.
+//!
+Fraction ResolveMagnitudeWeightFactorForPoll(const Poll& poll)
+{
+    Fraction magnitude_weight_factor = Params().GetConsensus().DefaultMagnitudeWeightFactor;
+
+    // Find the current protocol entry value for Magnitude Weight Factor, if it exists.
+    ProtocolEntryOption protocol_entry = GetProtocolRegistry().TryLastBeforeTimestamp("magnitudeweightfactor", poll.m_timestamp);
+
+    // If their is an entry prior or equal in timestemp to the start of the poll and it is active then set the magnitude weight
+    // factor to that value. If the last entry is not active (i.e. deleted), then leave at the default.
+    if (protocol_entry != nullptr && protocol_entry->m_status == ProtocolEntryStatus::ACTIVE) {
+        magnitude_weight_factor = Fraction().FromString(protocol_entry->m_value);
+    }
+
+    return magnitude_weight_factor;
+}
+
 } // Anonymous namespace
 
 // -----------------------------------------------------------------------------
@@ -1186,7 +1213,8 @@ PollResultOption PollResult::BuildFor(const PollReference& poll_ref)
         if (result.m_poll.IncludesMagnitudeWeight()) {
             counter.EnableMagnitudeWeight(
                 ResolveSuperblockForPoll(result.m_poll),
-                ResolveMoneySupplyForPoll(result.m_poll));
+                ResolveMoneySupplyForPoll(result.m_poll),
+                ResolveMagnitudeWeightFactorForPoll(result.m_poll));
         }
 
         LogPrint(BCLog::LogFlags::VOTE, "INFO: %s: number of votes = %u for poll %s",