# Swiplserver: error or long execution time in multiprocessing application

**URL:** <https://swi-prolog.discourse.group/t/swiplserver-error-or-long-execution-time-in-multiprocessing-application/5066>\
**Category:** Help!\
**Created:** [February 26, 2022, 6:36pm UTC](https://swi-prolog.discourse.group/t/swiplserver-error-or-long-execution-time-in-multiprocessing-application/5066 "2022-02-26T18:36:53Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Losbarthos](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/losbarthos/32/4037_2.png) [@Losbarthos](https://swi-prolog.discourse.group/u/Losbarthos)\
**Post date:** [February 26, 2022, 6:36pm UTC](https://swi-prolog.discourse.group/t/swiplserver-error-or-long-execution-time-in-multiprocessing-application/5066/1 "2022-02-26T18:36:53Z")

</div>

I’m using swiplserver and my aim is to control it in some multiprocessing application in python. My application loads some .pl file (say test.pl) and so it costs much time to init the server every time in the loop with e.g.:

```prolog
 with PrologMQI() as mqi:
    with mqi.create_thread() as prolog_thread:
    prolog_thread.query(f"consult('{PL_TEST}').")
    result = prolog_thread.query("test().")
    print(result)

```

My Idea now is to initiate the server only once (see function ‘ **get\_new\_prolog** ’) at the start of the process or alternative at the start of the program itself. Here is some code example of my problem (here I start the server once at start of every process):

**Prolog file (test.pl):**

```prolog
test():-
	false.

```

**Python file:**

```prolog
import multiprocessing

from config import *
from pathlib import Path
from swiplserver import PrologMQI, json_to_prolog

ROOT_DIR = Path( __file__ ).parent.parent
PL_TEST = f"{ROOT_DIR}/prolog/test.pl"

def get_new_prolog():
	MQI = PrologMQI()
	MQI.start()

	PL = MQI.create_thread()
	PL.start()
	PL.query(f"consult('{PL_TEST}').")
	return PL

def find(process, initial, PL ):
	succ = False
	i = 0
	print(f"Init: {process}")
	while i < 50:
# with PrologMQI() as mqi:
# with mqi.create_thread() as prolog_thread:
# prolog_thread.query(f"consult('{PL_TEST}').")
# result = prolog_thread.query("test().")
# print(result)
			PL.query(f"test().")
			i = i + 1

threads = []
PL = get_new_prolog()
processes = []
manager = multiprocessing.Manager()
queue = multiprocessing.Queue(maxsize=1)

for i in range(2):
	process = multiprocessing.Process(target=find, args=(f'computer_{i}', i, PL))
	processes.append(process)
	process.start()

ret = queue.get()
for i in range(2):
    process = processes[i]
    process.terminate()
    print(f'terminated {i}')

print(ret)

```

If I execute this I get the error:

```prolog
  File "/usr/lib/python3.9/multiprocessing/process.py", line 315, in _bootstrap
    self.run()
  File "/usr/lib/python3.9/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/home/martin/Dokumente/Programme/git/my/Beginning-Logic/python/test.py", line 29, in find
    PL.query(f"test().")
  File "/home/martin/.local/lib/python3.9/site-packages/swiplserver/prologmqi.py", line 682, in query
    return self._return_prolog_response()
  File "/home/martin/.local/lib/python3.9/site-packages/swiplserver/prologmqi.py", line 831, in _return_prolog_response
    raise {
swiplserver.prologmqi.PrologError: unknownCommand

```

As solution I could uncomment the lines

```prolog
# with PrologMQI() as mqi:
# with mqi.create_thread() as prolog_thread:
# prolog_thread.query(f"consult('{PL_TEST}').")
# result = prolog_thread.query("test().")
# print(result)

```

and comment the following line

```prolog
PL.query(f"test().")

```

but this costs a lot of time. Is their a way to:

1. Get a quick execution time
2. Solve the error above?

---

<div class="post-metadata">

**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\
**Post date:** [February 28, 2022, 12:14pm UTC](https://swi-prolog.discourse.group/t/swiplserver-error-or-long-execution-time-in-multiprocessing-application/5066/2 "2022-02-28T12:14:30Z")

</div>

This is cross [posted](https://stackoverflow.com/q/71294782/1243762) on StackOverflow.