The address you got is nothing but a loopback address. I mean, that's not the real IP address of your network interfaces, and is only used for self communications through the sockets interface. In Linux, you can determine the IP address of your network interface with something like: /sbin/ifconfig eth0 (you may need to replace eth0 with the identifier of your network interface, but in most cases this should work). You should assign different IP addresses to all your computers in the same network in order to be able to perform any communication among them. You most likely will want to assign private addresses, such as 192.168.0.1, 192.168.0.2, etc. You can easily find how to do this by googling a little bit. Antonio On Wednesday, October 23, 2013 11:10:48 PM Alexandra Betouni wrote: Well yes, the job runs on host2 locally, but parallel execution does the same thing like on host1. Someone here said that if all the computers have the same ip direction it won't work.. Well, every node has 127.0.1.1 As ip, and all of them had same host name till I changed the two of them. Hydra is the default launcher. I also forgot to mencione that ping host2 and same, ping host1 works fine... Sent from my BlackBerry 10 smartphone. *From: *[email protected] *Sent: *Wednesday, 23 October 2013 22:42 *To: *[email protected] *Reply To: *[email protected] *Subject: *discuss Digest, Vol 12, Issue 13 Send discuss mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://lists.mpich.org/mailman/listinfo/discuss[1] _https://lists.mpich.org/mailman/listinfo/discuss_ _https://lists.mpich.org/mailman/listinfo/discuss_ _https://lists.mpich.org/mailman/listinfo/discuss_ _https://lists.mpich.org/mailman/listinfo/discuss_ _https://lists.mpich.org/mailman/listinfo/discuss_ http://lists.mpich.org/pipermail/discuss/attachments/20131023/fdf9d820/at tachment-0001.html[2]> ------------------------------ Message: 3Date: Wed, 23 Oct 2013 17:27:27 -0200From: Luiz Carlos da Costa Junior <[email protected]>To: MPICH Discuss <mpich- [email protected]>Subject: [mpich-discuss] Failed to allocate memory for an unexpected messageMessage-ID: <[email protected] l.com>Content-Type: text/plain; charset="iso-8859-1" Hi, I am getting the following error when running my parallel application: MPI_Recv(186)......................: MPI_Recv(buf=0x125bd840, count=2060,MPI_CHARACTER, src=24, tag=94, comm=0x84000002, status=0x125fcff0) failedMPIDI_CH3I_Progress(402)...........:MPID_nem_mpich2_blocking_recv(90 5).:MPID_nem_tcp_connpoll(1838)........:state_commrdy_handler(1676)........ :MPID_nem_tcp_recv_handler(1564)....:MPID_nem_handle_pkt(636)...........:M PIDI_CH3_PktHandler_EagerSend(606): Failed to allocate memory for anunexpected message. 261895 unexpected messages queued.Fatal error in MPI_Send: Other MPI error, error stack:MPI_Send(173)..............: MPI_Send(buf=0x765d2e60, count=2060,MPI_CHARACTER, dest=0, tag=94, comm=0x84000004) failedMPID_nem_tcp_connpoll(1826): Communication error with rank 1: Connectionreset by peer I went to MPICH's FAQ ( http://wiki.mpich.org/mpich/index.php/Frequently_Asked_Questions#Q:_Why _am_I_getting_so_many_unexpected_messages.3F[3] http://lists.mpich.org/pipermail/discuss/attachments/20131023/3a02fa51/a ttachment-0001.html[4]> ------------------------------ Message: 4Date: Wed, 23 Oct 2013 14:42:15 -0500From: Antonio J. Pe?a <[email protected]>To: [email protected]: MPICH Discuss <mpich- [email protected]>Subject: Re: [mpich-discuss] Failed to allocate memory for an unexpected messageMessage-ID: <[email protected]>Content-Type: text/plain; charset="iso-8859-1" Hi Luiz, Your error trace indicates that the receiver went out of memory due to a too large amount (261,895) of eager unexpected messages received, i.e., small messages received without a matching receive operation. Whenever this happens, the receiver allocates a temporary buffer to hold the received message. This exhausted the available memory in the computer where the receiver was executing. To avoid this, try to pre-post receives before messages arrive. Indeed, this is far more efficient. Maybe you could do an MPI_IRecv per worker in your writer process, and process them after an MPI_Waitany. You may also consider having multiple writer processes if your use case permits and the volume of received messages is too high to be processed by a single writer. Antonio On Wednesday, October 23, 2013 05:27:27 PM Luiz Carlos da Costa Junior wrote: Hi, I am getting the following error when running my parallel application: MPI_Recv(186)......................: MPI_Recv(buf=0x125bd840, count=2060, MPI_CHARACTER, src=24, tag=94, comm=0x84000002, status=0x125fcff0) failed MPIDI_CH3I_Progress(402)...........: MPID_nem_mpich2_blocking_recv(905).: MPID_nem_tcp_connpoll(1838)........: state_commrdy_handler(1676)........: MPID_nem_tcp_recv_handler(1564)....: MPID_nem_handle_pkt(636)...........: MPIDI_CH3_PktHandler_EagerSend(606): Failed to allocate memory for an unexpected message. 261895 unexpected messages queued. Fatal error in MPI_Send: Other MPI error, error stack:MPI_Send(173)..............: MPI_Send(buf=0x765d2e60, count=2060, MPI_CHARACTER, dest=0, tag=94, comm=0x84000004) failed MPID_nem_tcp_connpoll(1826): Communication error with rank 1: Connection reset by peer I went to MPICH's FAQ (http://wiki.mpich.org/mpich/index.php/Frequently_Asked_Questions#Q:_Wh y_am_I_getting_so_many_unexpected_messages.3F[1]). It says that most likely the receiver process can't cope to process the high number of messages it is receiving.