PARDISO generates different results

Dear all,

I use PARDISO to solve a symmetric sparse matrix with size n=400,000 and number of nonzero=1,100,000. When I set the number of thread to one, I can get the same answer every time. But when I set the number of threads higher than 1 and run it many times, the answers become different every time (and never same as the answer by one thread). Are these weird results related to the issues of condition number or something else?

By the way, I have tried both  MKL 11.0.2 and 11.2.3.

Regards,

Gisiu