Assertion `ncp->head != ((void *)0)' failed.

[Wei-keng Liao]

I suggest you check the return value of your nonblocking call like below.
  err = ncmpi_iget_vara( ... );
  if (err != NC_NOERR)
      printf("Error: %s\n", ncmpi_strerror(err));

You can use as many ncmpi_iget_vara() calls to the same/different variables as you like.

I also suggest you to give a try to the latest SVN source. It has a new improvement
for the same-variable cases.
See instructions in http://trac.mcs.anl.gov/projects/parallel-netcdf/wiki/Download

Wei-keng

On Feb 13, 2013, at 1:43 PM, Liu, Jaln wrote:

> Hi Dr. Liao,
> 
> Thank you. Other ncmpi call works fine, like  ncmpi_get_vara_float and ncmpi_get_vara_float_all,
> 
>> Also, I am seeing this line in your codes:
>>       nb_temp_in[rank]=calloc(varasize,sizeof(float));
> 
> Yes, it should be `nb_temp'.
> 
> I wonder can we use ncmpi_iget_vara() on the same variable but different starts&lengths. From the sample program, it is used for multiple variables.
> 
> Jialin
> ________________________________________
> From: parallel-netcdf-bounces at lists.mcs.anl.gov [parallel-netcdf-bounces at lists.mcs.anl.gov] on behalf of Wei-keng Liao [wkliao at ece.northwestern.edu]
> Sent: Wednesday, February 13, 2013 1:28 PM
> To: parallel-netcdf at lists.mcs.anl.gov
> Subject: Re: Assertion `ncp->head != ((void *)0)' failed.
> 
> Hi, Jialin,
> 
> I suspect it is because the call to ncmpi_iget_vara() failed.
> Please check the return values of all your ncmpi_ calls.
> It may tell you if you got an error before you would like to continue.
> 
> Also, I am seeing this line in your codes:
>>       nb_temp_in[rank]=calloc(varasize,sizeof(float));
> 
> But you are using nb_temp[rank] in ncmpi_iget_vara()
> 
> 
> Wei-keng
> 
> On Feb 13, 2013, at 12:13 PM, Liu, Jaln wrote:
> 
>> Hi,
>> 
>> When I run the codes below, I got an error " Assertion `ncp->head != ((void *)0)' failed."
>> (I looked into the source codes, I saw a operation of checking Id, seems each request should be checked and matched with the file handle? I don't know the reason)
>> 
>>       float ** nb_temp;
>>       nb_temp=malloc(nprocs*sizeof(float *));
>>       int * request=calloc(nprocs, sizeof(int));
>>       int * status=calloc(nprocs,sizeof(int));
>>       mpi_start[1]=rank*5;//starts on other dimensions are specified to 0.
>>       int varasize=100*10*NLAT*NLON;
>>       nb_temp_in[rank]=calloc(varasize,sizeof(float));
>> 
>>       ncmpi_iget_vara(ncid, temp_varid, mpi_start,mpi_count,nb_temp[rank],varasize,MPI_FLOAT,&(request[rank]);
>> 
>>       ncmpi_wait_all(ncid, nprocs, request, status);
>> 
>> A detailed return is in the attachment,
>> 
>> Can you please tell me what's wrong with the codes?
>> I appreciate it.
>> 
>> Jialin
>> <56034.e>