Update parallel_miner_v3.py

parallel_miner_v3.py

@@ -134,7 +134,7 @@ class MiningCore:
 
 class ParallelMiner:
     """Top-level parallel miner managing multiple cores"""
-    def __init__(self, num_cores: int = 2, wallet_address: str = None):
+    def __init__(self, num_cores: int = 4, wallet_address: str = None):
         self.cores = [MiningCore(i) for i in range(num_cores)]
         self.start_time = None
         self.mining = False