Error when calculating PFC with multiple threads

[HPShark]

I defined PFC pfc(AES_SECURITY); in the main function, And refer to the openMP library and threadmp.cpp to calculate pk = pfc.mult(g, s); with multiple threads:

//omp_set_num_threads(1);	// pass
omp_set_num_threads(2);	// error
#pragma omp parallel for
	for (int i = 0; i < 100; i++)
	{
		G1 pk;
		pk = pfc.mult(g, s);      // public key
		cout << pk.g << endl;
	}

but an error will be reported during execution, and the content of each error report is different. The following is the content of a certain error report:

MIRACL error from routine nres_modadd
              called from nres_modmult
              called from ecurve_add
              called from nres_modmult
              called from ecurve_add
              called from your program
Overflow - Number too big

I also tried other multithreading libraries, mutexes, and web frameworks (crow) to try parallel computing, but I still can't solve the problem of pfc parameter passing.

How should I use pfc functions such as pfc.hash_to_aes_key(), pfc.pairing(), pfc.hash_and_map(), etc. in multithreading? Thanks a lot!

I am using Visual Studio 2022 on Windows 11 to compile and execute the code through Debug-win32. The complete code of the main.cpp and mirdef.h files is as follows:

// main.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <cstring>
#include<omp.h>
#define _CRT_SECURE_NO_WARNINGS

//security define
#define AES_SECURITY 128
#define MR_PAIRING_SSP
#include "pairing_1.h"
#include "ssp_pair.h"
#include "miracl.h"
#include "mirdef.h"
using namespace std;


int main()
{
	PFC pfc(AES_SECURITY);
	
	G1 g,pk;
	Big s;
	time_t seed;
	time(&seed);
	irand((long)seed);

	pfc.random(g);
	pfc.precomp_for_mult(g);	// precompute on fixed g
	pfc.random(s);				// mk=s


	//omp_set_num_threads(1);	// pass
	 omp_set_num_threads(2);	// error

#pragma omp parallel for
	for (int i = 0; i < 100; i++)
	{
		G1 pk;
		pk = pfc.mult(g, s);      // public key
		cout << pk.g << endl;
	}
}

// mirdef.h

#define MIRACL 32
#define MR_LITTLE_ENDIAN    /* This may need to be changed        */
#define mr_utype int
                            /* the underlying type is usually int *
                             * but see mrmuldv.any                */
#define mr_unsign32 unsigned int
                            /* 32 bit unsigned type               */
#define MR_IBITS      32    /* bits in int  */
#define MR_LBITS      32    /* bits in long */
#define MR_FLASH      52      
                            /* delete this definition if integer  *
                             * only version of MIRACL required    */
                            /* Number of bits per double mantissa */

#define mr_dltype __int64   /* ... or long long for Unix/Linux */
#define mr_unsign64 unsigned __int64

#define MAXBASE ((mr_small)1<<(MIRACL-1))


#define MR_OPENMP_MT