I've been trying to wrap my head around multiprocessing using an old python bitcoin mining program. Although relatively useless for mining, I figured this would be a great way to explore multiprocessing. However, I've hit a wall when it comes to stopping the processes when one of them achieves the goal they are all working towards.
I want to kill all multiprocessing pools when one of them finds the solution. Then allow the program to continue. I have tried terminate() and join(). I've attempted to include an Event(). I've tried using Process instead of Pool with the direction of a similar issue here: Killing a multiprocessing process when condition is met. However, same problem. How can I stop all processes after a condition is met without exiting the program with something like sys.exit() that would kill the entire program?
I tried also apply_sync with the direction from this post: Python Multiprocess Pool. How to exit the script when one of the worker process determines no more work needs to be done? However, it did not solve the problem of needing to continue executing the final functions of the program. In fact, it actually slowed the program significantly.
For clarity, I've included the code I tried based on the above mentioned link here:
from multiprocessing import Pool
from hashlib import sha256
import time
def SHA256(text):
return sha256(text.encode("ascii")).hexdigest()
def solution_helper(args):
solution, nonce = do_job(args)
if solution:
print(f"\nNonce Found: {nonce}\n")
return True
else:
return False
class Mining():
def __init__(self, workers, initargs):
self.pool = Pool(processes=workers, initargs=initargs)
def callback(self, result):
if result:
print('Solution Found...Terminating Processes...')
self.pool.terminate()
def do_job(self):
for args in values:
start_nonce = args[0]
end_nonce = args[1]
prefix_str = '0'*difficulty
self.pool.apply_async(solution_helper, args=args, callback=self.callback)
start = time.time()
for nonce in range(start_nonce, end_nonce):
text = str(block_number) + transactions + previous_hash + str(nonce)
new_hash = SHA256(text)
if new_hash.startswith(prefix_str):
print(f"Hashing: {text}")
print(f"\nSuccessfully mined bitcoin with nonce value: {nonce}\n")
print(f"New hash: {new_hash}")
total_time = str((time.time()-start))
print(f"\nEnd mning... Mining took {total_time} seconds\n")
return new_hash, nonce
self.pool.close()
self.pool.join()
print('.Goodbye.')
block_number = 5
transactions = """
bill->steve->20,
jan->phillis->45
"""
previous_hash = '0000000b7c7723e4d3a8654c975fe4dd23d4d37f22d0ea7e5abde2225d1567dc6'
values = [(20000, 100000), (100000, 1000000), (1000000, 10000000), (10000000, 100000000)]
difficulty = 4
m = Mining(5, values)
m.do_job()
Here's the basic concept. It works great to start the processes, but I cannot figure out how to stop them:
from multiprocessing import Pool
from hashlib import sha256
import functools
MAX_NONCE = 1000000000
def SHA256(text):
return sha256(text.encode("ascii")).hexdigest()
def nonce(block_number, transactions, previous_hash, prefix_str):
import time
start = time.time()
for nonce in range(MAX_NONCE):
text = str(block_number) + transactions + previous_hash + str(nonce)
new_hash = SHA256(text)
if new_hash.startswith(prefix_str):
print(f"\nYay! Successfully mined bitcoins with nonce value:{nonce}")
total_time = str((time.time()-start))
print(f"\nend mining. Mining took: {total_time} seconds\n")
print(new_hash + "\n")
def mine(block_number, transactions, previous_hash, prefix_zeros):
from multiprocessing import Pool
with Pool(4) as p:
prefix_str = '0'*prefix_zeros
p.map(nonce(block_number, transactions, previous_hash, prefix_str), [20000, 40000, 60000, 80000, 100000])
if __name__=='__main__':
transactions="""
bill->steve->20,
jan->phillis->45
"""
difficulty=7
print("\nstart mining\n")
new_hash = mine(5, transactions, '0000000b7c7723e4d3a8654c975fe4dd23d4d37f22d0ea7e5abde2225d1567dc6', difficulty)
# Do some other things... Here is where I'd like to get to after the multiproccesses are killed
print(f"\nMission Complete...{new_hash}\n") <---This never gets a chance to happen
