Hi I am trying to scatter some values to workers and then gather them. But I get strange error in gather step. Any suggestions? Below is the code and error file. //mpicxx test-boost.cpp -o test-boost -I /home1/mutlu/boost/include/boost-1_37/ /home1/mutlu/boost/lib/libboost_mpi-gcc41-mt-1_37.a #include <boost/mpi/environment.hpp> #include <boost/mpi/communicator.hpp> #include <boost/mpi/collectives.hpp> #include <boost/thread/mutex.hpp> #include <iostream> #include <vector> #define MASTER 0 namespace mpi = boost::mpi; using namespace std; struct x{ string name; int age; }; int arraySize = 23; void silly_func(int *px, int sz){ for(int i = 0; i < sz; i++) px[i] = 100; } int main(int argc, char* argv[]) { mpi::environment env(argc, argv); mpi::communicator world; int m_mySize, w_mySize, kk,i; int *myValues; vector<int> a; vector<int> aa; for(int i = 0; i < arraySize; i++) a.push_back(i); w_mySize = arraySize / world.size(); if (world.rank() == MASTER){ m_mySize = arraySize / world.size() + arraySize % world.size(); myValues = (int *) malloc(m_mySize); } else{ myValues = (int *) malloc(w_mySize); } if (world.rank() == MASTER) scatter(world, a, myValues, w_mySize, 0); else scatter(world, a, myValues, w_mySize, 0); if (world.rank() == MASTER) // append the remaining elements { for (i = w_mySize * world.size(), kk = 0; i < arraySize; i++, kk++) myValues[w_mySize + kk] = a[w_mySize * world.size() + kk]; } cout << "my rank is " << world.rank() << " and my values are" << endl; if (world.rank() == MASTER) for (int i = 0; i < m_mySize; i++) cout << myValues[i] << endl; if (world.rank() != MASTER) for (int i = 0; i < w_mySize; i++) cout << myValues[i] << endl; if (world.rank() != MASTER) silly_func(myValues, w_mySize); else silly_func(myValues, m_mySize); if (world.rank() == MASTER) gather(world, myValues, m_mySize, aa, 0); else gather(world, myValues, w_mySize, aa, 0); if (world.rank() == MASTER){ cout << "======================="<< endl; for(int i = 0; i < aa.size(); i++) cout << aa[i] << endl; } } and error file is [ceng3:23784] *** Process received signal *** [ceng3:23784] Signal: Segmentation fault (11) [ceng3:23784] Signal code: Address not mapped (1) [ceng3:23784] Failing at address: (nil) [ceng3:23784] [ 0] /lib64/libpthread.so.0 [0x30e100de80] [ceng3:23784] [ 1] /lib64/libc.so.6(memcpy+0x37) [0x30e047a107] [ceng3:23784] [ 2] /usr/mpi/gcc/openmpi-1.2.8/lib64/libmpi.so.0(ompi_ddt_copy_content_same_ddt+0xe8) [0x2b180e3b5618] [ceng3:23784] [ 3] /usr/mpi/gcc/openmpi-1.2.8/lib64/libmpi.so.0(ompi_ddt_sndrcv+0x3f3) [0x2b180e3b3ef3] [ceng3:23784] [ 4] /usr/mpi/gcc/openmpi-1.2.8/lib64/openmpi/mca_coll_basic.so(mca_coll_basic_gather_intra+0xd2) [0x2b18142f20a2] [ceng3:23784] [ 5] /usr/mpi/gcc/openmpi-1.2.8/lib64/libmpi.so.0(PMPI_Gather+0x19b) [0x2b180e3c7ccb] [ceng3:23784] [ 6] test-boost(_ZN5boost3mpi6detail11gather_implIiEEvRKNS0_12communicatorEPKT_iPS6_iN4mpl_5bool_ILb1EEE+0x6b) [0x414b29] [ceng3:23784] [ 7] test-boost(_ZN5boost3mpi6gatherIiEEvRKNS0_12communicatorEPKT_iPS5_i+0x50) [0x414c82] [ceng3:23784] [ 8] test-boost(_ZN5boost3mpi6gatherIiEEvRKNS0_12communicatorEPKT_iRSt6vectorIS5_SaIS5_EEi+0x42) [0x414ce8] [ceng3:23784] [ 9] test-boost(main+0x342) [0x40f62c] [ceng3:23784] [10] /lib64/libc.so.6(__libc_start_main+0xf4) [0x30e041d8b4] [ceng3:23784] [11] test-boost(__gxx_personality_v0+0x141) [0x40f199] [ceng3:23784] *** End of error message *** mpirun noticed that job rank 0 with PID 23784 on node ceng3-ib exited on signal 11 (Segmentation fault).