Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] Unexpected Behavior with C++ New Memory Allocation and MPI IO
From: Brian Budge (brian.budge_at_[hidden])
Date: 2013-06-12 19:50:25


You appear to be using new and delete[] together. Instead you should
be using new[] and delete[] and new and delete together.

  Brian

On Wed, Jun 12, 2013 at 4:44 PM, Corey Allen
<corey.allen_at_[hidden]> wrote:
> I have done a search on this and I haven't found an explanation. I am not a
> C/C++ nor MPI expert. I am getting a strange error when I use the C++ new
> keyword to allocate memory and then call a file read on OpenMPI. (Tech
> detail: 4-core Intel running Ubuntu 64-bit and OpenMPI 1.4.5. Everything is
> local. Total processes is 5.)
>
> In the source code you can see three different approaches to allocating the
> memory for the char array where the file's contents will go. With the
> C-style and MPI Alloc choices, there is no error even with buffer sizes in
> the MB range. However, if I use the C++ new keyword, I get an error for any
> read larger than 24 bytes.
>
> As I say, I'm not a C/C++ expert, but if I'm writing C++ code I was under
> the impression it was wise to use the C++ new approach rather than malloc.
> Am I missing something in getting this to work with MPI?
>
> Error (the important bit):
>
> *** glibc detected *** MPIIO_Test: free(): invalid next size (fast):
> 0x00000000015524e0 ***
>
> Code:
>
> int main(int argc, char* argv[]){
> int my_rank;
> MPI_Status status ;
> int errorCode;
> MPI_File _filehandle;
>
> MPI_Init(&argc, &argv);
> MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
>
> // Open File
> errorCode = MPI_File_open(MPI_COMM_WORLD, "TEST1A", MPI_MODE_RDONLY,
> MPI_INFO_NULL, &_filehandle);
>
> if (errorCode != 0)
> {
> int errorStringLen;
> char *errorString = (char*) malloc(MPI_MAX_ERROR_STRING);
>
> // Get MPI file I/O error string and print it
> MPI_Error_string(errorCode, errorString, &errorStringLen);
>
> printf("MPI Error opening Data File: %s \n", errorString);
>
> free(errorString);
> }
>
> // Works with new at 24, fails at 25
> int dataLength = 25, numBytesRead;
> char *data = NULL;
> // data = (char*) malloc(dataLength);
> data = new char(dataLength);
> // MPI_Alloc_mem(dataLength, MPI_INFO_NULL, &data);
>
> // File I/O
> errorCode = MPI_File_read_at(_filehandle, my_rank*dataLength, data,
> dataLength, MPI_CHAR, &status);
> MPI_Get_count(&status, MPI_CHAR, &numBytesRead);
> printf("Rank: %d Start: %d Expected: %d Read: %d \n", my_rank,
> my_rank*dataLength, dataLength, numBytesRead);
>
> if (errorCode != 0)
> {
> int errorStringLen;
> char *errorString = (char*) malloc(MPI_MAX_ERROR_STRING);
>
> // Get MPI file I/O error string and print it
> MPI_Error_string(errorCode, errorString, &errorStringLen);
>
> printf("MPI Error reading from Data File: %s \n", errorString);
>
> free(errorString);
> }
>
> // Free memory
> // free(data);
> delete[] data;
> // MPI_Free_mem(data);
>
> // Close file
> MPI_File_close(&_filehandle);
>
> MPI_Finalize();
> return 0;
> }
>
>
>
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users