MPI\_Scatter and MPI\_Scatterv APIs
mpi.scatter and mpi.scatterv are the inverse operations of
mpi.gather and mpi.gatherv respectively.
mpi.scatter(x, type, rdata, root = 0, comm = 1) mpi.scatterv(x, scounts, type, rdata, root = 0, comm = 1)
x |
data to be scattered. |
type |
1 for integer, 2 for double, and 3 for character. Others are not supported. |
rdata |
the receive buffer. Must be the same type as the sender |
scounts |
int vector specifying the block length inside a message to be scattered to other members. |
root |
rank of the receiver |
comm |
a communicator number |
mpi.scatter scatters the message x to all members. Each member receives
a portion of x with dim as length(x)/size in rank order, where size is the
total number of members in a comm. So the receive buffer can be prepared as
either integer(length(x)/size) or double(length(x)/size). For
mpi.scatterv, scounts counts the portions (different dims) of x sent to
each member. Each member needs to prepare the receive buffer as either
integer(scounts[i]) or double(scounts[i]).
For non-root members, mpi.scatter or scatterv returns the
scattered message and ignores whatever is in x (or scounts). For the root
member, it returns the portion belonging to itself.
Hao Yu
#Need 3 slaves to run properly #Or run mpi.spawn.Rslaves(nslaves=3) num="123456789abcd" scounts<-c(2,3,1,7) mpi.bcast.cmd(strnum<-mpi.scatter(integer(1),type=1,rdata=integer(1),root=0)) strnum<-mpi.scatter(scounts,type=1,rdata=integer(1),root=0) mpi.bcast.cmd(ans <- mpi.scatterv(string(1),scounts=0,type=3,rdata=string(strnum), root=0)) mpi.scatterv(as.character(num),scounts=scounts,type=3,rdata=string(strnum),root=0) mpi.remote.exec(ans)
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