Point-to-Point Communication
Contents
Point-to-Point Communication¶
Sending data from one point (process/task) to another point (process/task)
send/recv¶
using MPI
MPI.Init()
comm = MPI.COMM_WORLD
rank = MPI.Comm_rank(comm)
size = MPI.Comm_size(comm)
struct Point
x::Float64
y::Float64
end
p = Point(rank, rank)
if rank == 0
MPI.send(p, comm; dest=1)
elseif rank > 0
data = MPI.recv(comm; source=(rank - 1))
MPI.send(p, comm; dest=(rank + 1) % size)
end
if rank == 0
data = MPI.recv(comm; source=(size - 1))
end
print("My rank is $(rank)\n I received this: $(data)\n")
MPI.Barrier(comm)
If the preceding code is saved as a file send_recv.jl, we can run
!~/.julia/bin/mpiexecjl --project=.. -np 3 julia send_recv.jl
ERROR: ERROR:
LoadError: ERROR:
LoadError:
LoadError:
MethodError:
MethodError:
no method matching recv(
::
no method matching
send(::
MPI.Comm
; source=1
)
Point, ::MPI.Comm;
MethodError: dest=1)
Closest candidates are:
recv(!Matched::Integer, !Matched::Integer, !Matched::MPI.Comm) at ~/.julia/packages/MPI/08SPr/src/pointtopoint.jl:310 got unsupported keyword argument "source"
Stacktrace:
[1] top-level scope
no method matching
Closest candidates are:
send(::Any, !Matched::Integer, !Matched::Integer, !Matched::MPI.Comm) at ~/.julia/packages/MPI/08SPr/src/pointtopoint.jl:207 got unsupported keyword argument "dest"
Stacktrace:
[1] top-level scope
recv(
::
@ ~/work/hpc-book/hpc-book/src/
@ ~/work/hpc-book/hpc-book/src/send_recv.jl:17
in expression starting at /home/runner/work/hpc-book/hpc-book/src/send_recv.jl:16
===================================================================================
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= PID 3303 RUNNING AT fv-az91-811
= EXIT CODE: 9
= CLEANING UP REMAINING PROCESSES
= YOU CAN IGNORE THE BELOW CLEANUP MESSAGES
===================================================================================
YOUR APPLICATION TERMINATED WITH THE EXIT STRING: Killed (signal 9)
This typically refers to a problem with your application.
Please see the FAQ page for debugging suggestions
ERROR:
failed process: Process(`
/home/runner/.julia/artifacts/af2355b4e003d5800b907f71eaf64c62b6e365f1/bin/mpiexec -np 3 julia send_recv.jl`, ProcessExited(9)) [9]
Stacktrace:
[1] pipeline_error
@ ./process.jl:531 [inlined]
[2] run(::Cmd; wait::Bool)
@ Base ./process.jl:446
[3] run(::Cmd)
@ Base process.jl:444
[4] (::var"#1#2")(exe::Cmd)
@ Main none:4
[5] (::MPI.var"#10#11"{var"#1#2"})(cmd::String)
@ MPI ~/.julia/packages/MPI/08SPr/src/environment.jl:25
[6] (::JLLWrappers.var"#2#3"{MPI.var"#10#11"{var"#1#2"}, String})()
@ JLLWrappers ~/.julia/packages/JLLWrappers/QpMQW/src/runtime.jl:49
[7] withenv(::JLLWrappers.var"#2#3"{MPI.var"#10#11"{var"#1#2"}, String}, ::Pair{String, String}, ::Vararg{Pair{String, String}})
@ Base env.jl:172
[8] withenv_executable_wrapper(f::Function, executable_path::String, PATH::String, LIBPATH::String, adjust_PATH::Bool, adjust_LIBPATH::Bool)
@ JLLWrappers ~/.julia/packages/JLLWrappers/QpMQW/src/runtime.jl:48
[9] invokelatest(::Any, ::Any, ::Vararg{Any}; kwargs::Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
@ Base ./essentials.jl:716
[10] invokelatest(::Any, ::Any, ::Vararg{Any})
@ Base ./essentials.jl:714
[11] mpiexec(f::Function; adjust_PATH::Bool, adjust_LIBPATH::Bool)
@ MPICH_jll ~/.julia/packages/JLLWrappers/QpMQW/src/products/executable_generators.jl:21
[12] mpiexec(f::Function)
@ MPICH_jll ~/.julia/packages/JLLWrappers/QpMQW/src/products/executable_generators.jl:21
[13] mpiexec(fn::var"#1#2")
@ MPI ~/.julia/packages/MPI/08SPr/src/environment.jl:25
[14] top-level scope
@ none:4
Send/Recv¶
using MPI
MPI.Init()
comm = MPI.COMM_WORLD
rank = MPI.Comm_rank(comm)
size = MPI.Comm_size(comm)
send_buf = Array{Float64}(undef, 10)
recv_buf = Array{Float64}(undef, 10)
fill!(send_buf, Float64(rank))
if rank == 0
MPI.Send(send_buf, comm; dest=1)
elseif rank > 0
MPI.Recv!(recv_buf, comm; source=(rank - 1))
MPI.Send(send_buf, comm; dest=(rank + 1) % size)
end
if rank == 0
MPI.Recv!(recv_buf, comm; source=(size - 1))
end
print("My rank is $(rank)\n I received this: $(recv_buf)\n")
MPI.Barrier(comm)
If the preceding code is saved as a file Send_Recv.jl, we can run
!~/.julia/bin/mpiexecjl -np 3 julia Send_Recv.jl
ERROR:
ArgumentError: Package MPI not found in current path:
- Run `import Pkg; Pkg.add("MPI")` to install the MPI package.
Stacktrace:
[1] require(into::Module, mod::Symbol)
@ Base ./loading.jl:967
Isend/Irecv¶
using MPI
MPI.Init()
comm = MPI.COMM_WORLD
rank = MPI.Comm_rank(comm)
size = MPI.Comm_size(comm)
send_buf = Array{Float64}(undef, 10)
recv_buf = Array{Float64}(undef, 10)
fill!(send_buf, Float64(rank))
if rank == 0
send_status = MPI.Isend(send_buf, comm; dest=1)
elseif rank > 0
recv_status = MPI.Irecv!(recv_buf, comm; source=(rank - 1))
send_status = MPI.Isend(send_buf, comm; dest=(rank + 1) % size)
end
if rank == 0
recv_status = MPI.Irecv!(recv_buf, comm; source=(size - 1))
end
stats = MPI.Waitall!([send_status, recv_status])
print("My rank is $(rank)\n I received this: $(recv_buf)\n")
If the preceding code is saved as a file Isend_Irecv.jl, we can run
!~/.julia/bin/mpiexecjl -np 3 julia ISend_IRecv.jl
ERROR:
ArgumentError: Package MPI not found in current path:
- Run `import Pkg; Pkg.add("MPI")` to install the MPI package.
Stacktrace:
[1] require(into::Module, mod::Symbol)
@ Base ./loading.jl:967