cluster_sparse_solver can not release physical memory for rank=0 process

Hi:

   I find out that cluster_sparse_solver can not release physical memory for rank=0 process.

   I apply two processes and two threads for each process to solve mtype=6, complex and symmetric matrix and use distribute assembled matrix input format as well as distribute RHS elements. The full example is in the attachment file.

   The test I do is use literation statement to do the same calculation again and again. The result for every loop is correct. And the physical memory for rank=1 remains the same for each loop. However, the physical memory for rank=0 keeps on climbing. My computer has 16G memory and the physical memory occupation is shown below:

loop             rank=0(%)               rank=1(%)

         phase 11   phase 23

0       4.7            6.5                   4.6

1       5.7            7.4

2       6.6            8.3

3       7.5            9.3

4       8.4            10.2

5       9.4            11.2

I use the following command to compile: mpic++ -cxx=icpc -std=c++1y -mkl -xHost plain.cpp

and to run: mpiexec -n 2 ./a.out

I use mpich 3.1, mkl 11.2, icpc 15.0.0 on linux 64