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List Info
Thread: LAM: gatherv a vector
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| LAM: gatherv a vector |
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2006-10-24 20:45:07 |
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hi,
I am able to send/receive an stl vector of vectors (of integers)
using derived datatypes. Now I want to optimize my communicationby
using scatterv/gatherv, but I am having problems understanding how to
map my send/recv method into a collective communication.
My code is as follows
//function to build a derived datatype:
void buildDerivedDataType(vector< vector <int>; >
&Points, int d, int count, int displ, MPI_Datatype *MY_MPI_TYPE){
; int lena[count];
MPI_Aint loca[count];
MPI_Datatype typa[count];
; for (int i=0; i<count; ++i) {
lena[i] = d;
; MPI_Address(&Points[displ+i][0], &loca[i]);
; typa[i] = MPI_INT;
; }
MPI_Type_struct(count, lena, loca, typa, MY_MPI_TYPE);
; MPI_Type_commit(MY_MPI_TYPE);
}
//everybody sends to ROOT processor
MPI_Datatype MY_MPI_TYPE;
buildDerivedDataType(localSk, d, localSkSize, 0, &MY_MPI_TYPE);
MPI_Send(MPI_BOTTOM, 1, MY_MPI_TYPE, ROOT, 111, MPI_COMM_WORLD);
MPI_Type_free(&MY_MPI_TYPE);
....
//ROOT processor receives the vectors of vectors from each processor
//space for Points is already allocated
if(myID==ROOT){
MPI_Datatype MY_MPI_TYPE_R;
buildDerivedDataType(Points, d, receiveCount[k]/d, disp[k]/d, &MY_MPI_TYPE_R);
MPI_Recv(MPI_BOTTOM, 1, MY_MPI_TYPE_R, k, 111,
MPI_COMM_WORLD, &Stat);
MPI_Type_free(&MY_MPI_TYPE_R);
}
this works just fine, all my data is now at ROOT in the vector of
vector Points. But now I want to use mpi_gatherv instead of the above,
so I was trying something like this; "disp" has the displacements in
units of "int".
int cnt = 1;
; MPI_Gatherv(&localSk[0].front(), 1, MY_MPI_TYPE,
&Points[0].front(), &cnt, disp, MY_MPI_TYPE_R, ROOT,
MPI_COMM_WORLD);
MPI_Type_free(&MY_MPI_TYPE); ;
MPI_Type_free(&MY_MPI_TYPE_R);
Can anyone point me to the right direction as to what would the be the format of scatterv/gatherv in this situation?
thanks
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