pool: Calculate share weights dynamically.

This calculates the share weights in the global share weights map
dynamically based on the entires in the map of the miner hash rates
instead of hard-coding them to manually calculated values that can
easily become outdated when the hash rates are updated.

pool/share.go

@@ -13,13 +13,39 @@ import (
 )
 
 // ShareWeights represents the associated weights for each known DCR miner.
-// With the share weight of the lowest hash DCR miner (LHM) being 1, the
-// rest were calculated as:
 //
-//	(Hash of Miner X * Weight of LHM)/ Hash of LHM
-var ShareWeights = map[string]*big.Rat{
-	CPU: new(big.Rat).SetFloat64(1.0), // Reserved for testing.
-}
+// The weights are calculated as:
+//
+//	Hash of Miner X / Hash of LHM
+var ShareWeights = func() map[string]*big.Rat {
+	// In practice there will always be at least the CPU miner, however, be safe
+	// and return an empty map if the miner hashes somehow ends up empty in the
+	// future.
+	if len(minerHashes) == 0 {
+		return make(map[string]*big.Rat, len(minerHashes))
+	}
+
+	// Find the lowest hash rate miner.
+	lowestHashRate := big.NewInt(0)
+	for _, hashRate := range minerHashes {
+		if lowestHashRate.Sign() == 0 || hashRate.Cmp(lowestHashRate) < 0 {
+			lowestHashRate.Set(hashRate)
+		}
+	}
+
+	shareWeights := make(map[string]*big.Rat, len(minerHashes))
+	for miner, hashRate := range minerHashes {
+		// Ensure CPU is always a share weight of 1.0 as it is only valid in
+		// either testing scenarios or a CPU-only mining regime.
+		if miner == CPU {
+			shareWeights[CPU] = new(big.Rat).SetFloat64(1.0)
+			continue
+		}
+
+		shareWeights[miner] = new(big.Rat).SetFrac(hashRate, lowestHashRate)
+	}
+	return shareWeights
+}()
 
 // shareID generates a unique share id using the provided account, creation
 // time, and random uint64.