LAM: using an stl vector of vectors

Hi Adán,

Unfortunately using STL vectors will probably not work as
they are not 
guaranteed to have any particular memory layout, and MPI
requires a 
contiguous allocation of memory. 

This is a problem that has been studied and there was
recently a paper 
published about one way to solve it (http://dx.doi.o
rg/10.1007/11846802_39).

Hope this helps,

Tim

On Monday 23 October 2006 02:51 pm, Adán Cosgaya wrote:
> Hi,
>
> I am trying to scatterv/gatherv an stl vector of
vectors, but it doesn't
> seem to work, but if I try to do it using a 2d array,
it works fine, is
> there anything special in the way the memory is
allocated in the case of
> stl vectors, that is making it not to work correctly?.
>
> Here is my piece of code
> tmpSkyMatrix[size][d]
> vector <vector<int> > PointsTmp (size,
vector<int>(d)); //allocate space in
> the vector of vectors
> ....//do some computation
>
> //with a 2d matrix works fine
> MPI_Gatherv(skyMatrix, localSkySize, MPI::INT,
tmpSkyMatrix, receiveCount,
> disp, MPI::INT, ROOT, MPI_COMM_WORLD);
>
> //with a vector of vector crashes
> MPI_Gatherv(&localSkyline[0][0], localSkySize,
MPI::INT, &PointsTmp[0][0],
> receiveCount, disp, MPI::INT, ROOT, MPI_COMM_WORLD);
>
> In case you wonder why I rather use an stl vector, it
is because my
> computation is making use of some stl algorithms,  I
just need to send the
> resulting data accross the processor, but this data is
stored in a vector
> of vectors, and is very costly, to load that data into
a 2d array, then
> receive it, and load it in a vector of vectors again to
do some other
> processing.
>
> Thanks in advance

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