Hi, This is my first post to this mailing list. After working two month with mpich2 I decided to try the Intel MPI Benchmark. The strange thing is, that at compiling the sources, I get an linker error when mpicc wants to compile the files for the asynchronous communication. Further I can use the asynchronous function in my self-written programs without any problems or errors. So this is the command I execute: /home/rpimpi/mpich2-install/bin/mpicc -O0 -DNBC IMB.c IMB_declare.c IMB_init.c IMB_mem_manager.c IMB_parse_name_nbc.c IMB_benchlist.c IMB_strgs.c IMB_err_handler.c IMB_g_info.c IMB_warm_up.c IMB_output.c IMB_allreduce.c IMB_reduce_scatter.c IMB_reduce.c IMB_bcast.c IMB_barrier.c IMB_allgather.c IMB_allgatherv.c IMB_gather.c IMB_gatherv.c IMB_scatter.c IMB_scatterv.c IMB_alltoall.c IMB_alltoallv.c IMB_sendrecv.c IMB_init_transfer.c IMB_chk_diff.c IMB_cpu_exploit.c -o IMB-NBC And this is the output I get: /tmp/ccEEnyN2.o: In function `IMB_iallreduce': IMB_allreduce.c:(.text+0x1bc): undefined reference to `MPI_Iallreduce' /tmp/ccEEnyN2.o: In function `IMB_iallreduce_pure': IMB_allreduce.c:(.text+0x438): undefined reference to `MPI_Iallreduce' /tmp/cc3xs7IY.o: In function `IMB_ireduce_scatter': IMB_reduce_scatter.c:(.text+0x190): undefined reference to `MPI_Ireduce_scatter' /tmp/cc3xs7IY.o: In function `IMB_ireduce_scatter_pure': IMB_reduce_scatter.c:(.text+0x4a8): undefined reference to `MPI_Ireduce_scatter' /tmp/ccnDYI6U.o: In function `IMB_ireduce': IMB_reduce.c:(.text+0x1e4): undefined reference to `MPI_Ireduce' /tmp/ccnDYI6U.o: In function `IMB_ireduce_pure': IMB_reduce.c:(.text+0x488): undefined reference to `MPI_Ireduce' /tmp/ccsnt9EQ.o: In function `IMB_ibcast': IMB_bcast.c:(.text+0x1c0): undefined reference to `MPI_Ibcast' /tmp/ccsnt9EQ.o: In function `IMB_ibcast_pure': IMB_bcast.c:(.text+0x46c): undefined reference to `MPI_Ibcast' /tmp/ccW45dyI.o: In function `IMB_ibarrier': IMB_barrier.c:(.text+0xf0): undefined reference to `MPI_Ibarrier' /tmp/ccW45dyI.o: In function `IMB_ibarrier_pure': IMB_barrier.c:(.text+0x29c): undefined reference to `MPI_Ibarrier' /tmp/cc5Jqe5y.o: In function `IMB_iallgather': IMB_allgather.c:(.text+0x208): undefined reference to `MPI_Iallgather' /tmp/cc5Jqe5y.o: In function `IMB_iallgather_pure': IMB_allgather.c:(.text+0x4c4): undefined reference to `MPI_Iallgather' /tmp/cc1sWF8r.o: In function `IMB_iallgatherv': IMB_allgatherv.c:(.text+0x218): undefined reference to `MPI_Iallgatherv' /tmp/cc1sWF8r.o: In function `IMB_iallgatherv_pure': IMB_allgatherv.c:(.text+0x550): undefined reference to `MPI_Iallgatherv' /tmp/cce30p6o.o: In function `IMB_igather': IMB_gather.c:(.text+0x230): undefined reference to `MPI_Igather' /tmp/cce30p6o.o: In function `IMB_igather_pure': IMB_gather.c:(.text+0x514): undefined reference to `MPI_Igather' /tmp/ccQygcKr.o: In function `IMB_igatherv': IMB_gatherv.c:(.text+0x240): undefined reference to `MPI_Igatherv' /tmp/ccQygcKr.o: In function `IMB_igatherv_pure': IMB_gatherv.c:(.text+0x5a0): undefined reference to `MPI_Igatherv' /tmp/ccNpVNux.o: In function `IMB_iscatter': IMB_scatter.c:(.text+0x230): undefined reference to `MPI_Iscatter' /tmp/ccNpVNux.o: In function `IMB_iscatter_pure': IMB_scatter.c:(.text+0x514): undefined reference to `MPI_Iscatter' /tmp/ccRgsSLD.o: In function `IMB_iscatterv': IMB_scatterv.c:(.text+0x244): undefined reference to `MPI_Iscatterv' /tmp/ccRgsSLD.o: In function `IMB_iscatterv_pure': IMB_scatterv.c:(.text+0x5ac): undefined reference to `MPI_Iscatterv' /tmp/cceoMEjN.o: In function `IMB_ialltoall': IMB_alltoall.c:(.text+0x208): undefined reference to `MPI_Ialltoall' /tmp/cceoMEjN.o: In function `IMB_ialltoall_pure': IMB_alltoall.c:(.text+0x4c4): undefined reference to `MPI_Ialltoall' /tmp/ccbHoHAQ.o: In function `IMB_ialltoallv': IMB_alltoallv.c:(.text+0x230): undefined reference to `MPI_Ialltoallv' /tmp/ccbHoHAQ.o: In function `IMB_ialltoallv_pure': IMB_alltoallv.c:(.text+0x5c0): undefined reference to `MPI_Ialltoallv' collect2: ld returned 1 exit status I hope someone of you can help me concerning this problem. Greetings, Philip