Executing ghost through python causes error when multiple instances of variables of type AtomSpace are used

[Eyob]

Here is sample python code that runs with python3, but am sure would run with python2 as well.

The python code has two functions: chat_1 and chat_2. Each function even imports opencog bindings independently. But it seems when both
functions are executed one after the other, an error occurs (the error message found just after the python code).

My guess is the functions use two different variables "atomspace" and this seems to cause the error. But I can't figure out what the error means or what the real cause is.

The only way to solve this problem seems to use multiprocessing functionality. When multiprocessing is used by calling the proc( ) function in the code below, then
no errors come up. But when threading or simply calling the functions one after the other, the error appears (i.e. calling the functions thrd( ) and vanilla ( ) ).

Even calling the function chat_1 twice causes an error as done in the thrd ( ) function that uses separate threads to run the function chat_1 .

Here is sample python code and below it the  error that appears when either vanilla( ) or thrd( ) is called but not when proc( ) is called

# Tested on python3.4/3.5
import time
import multiprocessing
import threading

def chat_1():

    from opencog.atomspace import AtomSpace
    from opencog.scheme_wrapper import scheme_eval_h

    atomspace = AtomSpace()

    scheme_eval_h(atomspace, "(use-modules (opencog))")
    scheme_eval_h(atomspace, "(use-modules (opencog nlp relex2logic))")
    scheme_eval_h(atomspace, "(use-modules (opencog openpsi))")
    scheme_eval_h(atomspace, "(use-modules (opencog eva-behavior))")
    scheme_eval_h(atomspace, "(use-modules (opencog ghost))")

    print('len(atomspace) =',len(atomspace))

    scheme_query_1 = '(ghost-parse "s: (hi robot) Hello human")'
    scheme_query_2 = '(test-ghost "hi robot good morning")'

    scheme_eval_h(atomspace, scheme_query_1)

    print('len(atomspace) =', len(atomspace))

    scheme_eval_h(atomspace, scheme_query_2)

def chat_2():

    from opencog.atomspace import AtomSpace
    from opencog.scheme_wrapper import scheme_eval_h

    atomspace = AtomSpace()

    scheme_eval_h(atomspace, "(use-modules (opencog))")
    scheme_eval_h(atomspace, "(use-modules (opencog nlp relex2logic))")
    scheme_eval_h(atomspace, "(use-modules (opencog openpsi))")
    scheme_eval_h(atomspace, "(use-modules (opencog eva-behavior))")
    scheme_eval_h(atomspace, "(use-modules (opencog ghost))")

    print('len(atomspace) =',len(atomspace))

    scheme_query_1 = '(ghost-parse "s: (hi robot) Hello human")'
    scheme_query_2 = '(test-ghost "hi robot good morning")'

    scheme_eval_h(atomspace, scheme_query_1)

    print('len(atomspace) =', len(atomspace))

    scheme_eval_h(atomspace, scheme_query_2)

def vanilla():
    chat_1()
    time.sleep(5)
    chat_2()

def proc():
    p1 = multiprocessing.Process(target=chat_1)
    p1.start()
    # p1.join()
    # time.sleep(5)
    p2 = multiprocessing.Process(target=chat_2)
    p2.start()
    # p2.join()

def thrd():
    t1 = threading.Thread(target=chat_1)
    t1.start()
    time.sleep(5)
    t2 = threading.Thread(target=chat_1)
    t2.start()

if __name__ == '__main__':


    # proc()
    # thrd()
    # vanilla()

    pass

Error that appears when either calling vanilla( ) or thrd( ) but not proc( )

len(atomspace) = 3624
[2018-03-21 10:12:04:920] [WARN] [GHOST] Did you forget to link a goal to the rule?
len(atomspace) = 3825
[2018-03-21 10:12:04:990] [INFO] [GHOST] Say: "Hello human"
len(atomspace) = 0
Traceback (most recent call last):
  File "/***/pra5.py", line 96, in <module>
    vanilla()
  File "/***/pra5.py", line 63, in vanilla
    chat_2()
  File "/***/pra5.py", line 53, in chat_2
    scheme_eval_h(atomspace, scheme_query_1)
  File "scheme_wrapper.pyx", line 49, in opencog.scheme_wrapper.scheme_eval_h (/***/atomspace/build/opencog/cython/opencog/scheme_wrapper.cpp:1198)
RuntimeError: Backtrace:
In ice-9/boot-9.scm:
 157: 14 [catch #t #<catch-closure 1cc55a0> ...]
In unknown file:
   ?: 13 [apply-smob/1 #<catch-closure 1cc55a0>]
In ice-9/boot-9.scm:
 157: 12 [catch #t #<catch-closure 1cc5480> ...]
In unknown file:
   ?: 11 [apply-smob/1 #<catch-closure 1cc5480>]
   ?: 10 [call-with-input-string "(ghost-parse \"s: (hi robot) Hello human\")" ...]
In ice-9/boot-9.scm:
2320: 9 [save-module-excursion #<procedure 1848d20 at ice-9/eval-string.scm:65:9 ()>]
In ice-9/eval-string.scm:
  44: 8 [read-and-eval #<input: string 1b9d4e0> #:lang ...]
  37: 7 [lp (ghost-parse "s: (hi robot) Hello human")]
In system/base/lalr.upstream.scm:
1927: 6 [___run]
In opencog/ghost/cs-parse.scm:
 320: 5 [#<procedure 28adde0 (___stack ___sp ___goto-table ___push yypushback)> # ...]
In opencog/ghost/translator.scm:
 409: 4 [create-rule ((lemma . "hi") (lemma . "robot")) ((action # #)) () ...]
 215: 3 [process-pattern-terms (# # # #)]
In unknown file:
   ?: 2 [cog-new-link 58 #<Invalid handle> (VariableNode "$S")
]
In ice-9/boot-9.scm:
 102: 1 [#<procedure 159b200 at ice-9/boot-9.scm:97:6 (thrown-k . args)> C++-EXCEPTION ...]
In unknown file:
   ?: 0 [apply-smob/1 #<catch-closure 1cc5440> C++-EXCEPTION ...]

ERROR: In procedure apply-smob/1:
ERROR: In procedure cog-new-link: Expecting name and state, got size 1 (/***/atomspace/opencog/atoms/core/StateLink.cc:32)
Function args:
(#<Invalid handle> (VariableNode "$S")
)
ABORT: C++-EXCEPTION
 (/***/atomspace/opencog/guile/SchemeEval.cc:930)

Process finished with exit code 1