Help of multiple threads using cpython

[LM19952012]

I recently tried to use a lot of threads (i.e. about 100) to run the same python function. That function will call an external library written in C. However, cpython will periodically throw an error at the line of calling the external C function, which looks like the following:

Error:
Exception in thread Thread-34:
Traceback (most recent call last):
  File "/homes/liu1740/miniconda3/envs/my-rdkit-env/lib/python3.6/threading.py", line 916, in _bootstrap_inner
    self.run()
  File "/homes/liu1740/miniconda3/envs/my-rdkit-env/lib/python3.6/threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
  File "/u/subspace_s4/liu1740/Research/LocalGraphClustering/localgraphclustering/ncp.py", line 50, in ncp_node_worker
    ncpdata.results.extend(ncp_experiment(ncpdata, R, func, method_stats))
  File "/u/subspace_s4/liu1740/Research/LocalGraphClustering/localgraphclustering/ncp.py", line 26, in ncp_experiment
    S = func(ncpdata.graph, R)
  File "<ipython-input-4-a67f0813539b>", line 1, in <lambda>
    funcs = {lambda G,R: lgc.spectral_clustering(G,R,alpha=alpha,rho=rho,method="acl")[0]:'acl;rho=%.0e'%(rho) for rho in rholist}
  File "/u/subspace_s4/liu1740/Research/LocalGraphClustering/localgraphclustering/spectral_clustering.py", line 96, in spectral_clustering
    rho = rho, epsilon = epsilon, method = method, ys = ys)
  File "/u/subspace_s4/liu1740/Research/LocalGraphClustering/localgraphclustering/approximate_PageRank.py", line 115, in approximate_PageRank
    alpha,rho,ref_nodes,iterations,G.lib)
  File "/u/subspace_s4/liu1740/Research/LocalGraphClustering/localgraphclustering/cpp/aclpagerank_cpp.py", line 52, in aclpagerank_cpp
    actual_length=fun(n,ai,aj,flag,alpha,eps,seedids,nseedids,maxsteps,xids,xlength,values)
ctypes.ArgumentError: argument 11: <class 'TypeError'>: 'int' object is not callable

And it can happen at any argument randomly, not just argument 11. The code works fine with few threads. My guess is something is wrong during the conversion from a python variable to a C variable, but I am not sure and don't know how to fix it.