Add non-blocking wait

docs/src/reference/pointtopoint.md

@@ -55,6 +55,7 @@ MPI.Testall
 MPI.Testany
 MPI.Testsome
 MPI.Wait
+Base.wait(req::MPI.Request)
 MPI.Waitall
 MPI.Waitany
 MPI.Waitsome

src/nonblocking.jl

@@ -774,3 +774,14 @@ function Cancel!(req::AbstractRequest)
     API.MPI_Cancel(req)
     nothing
 end
+
+"""
+    Base.wait(req::MPI.Request)
+
+Wait for an MPI request to complete. Unlike [`MPI.Wait`](@ref), it will yield to other Julia tasks resulting in a cooperative wait.
+"""
+function Base.wait(req::MPI.Request)
+    while !MPI.Test(req)
+        yield()
+    end
+end

test/test_cooperative_wait.jl

@@ -0,0 +1,37 @@
+# tests for the various kinds of waits
+include("common.jl")
+
+MPI.Init()
+
+myrank = MPI.Comm_rank(MPI.COMM_WORLD)
+commsize = MPI.Comm_rank(MPI.COMM_WORLD)
+
+nsends = 2
+send_arr = [ArrayType{Int}([i]) for i = 1:nsends]
+recv_arr = [ArrayType{Int}(undef,1) for i = 1:nsends]
+synchronize()
+
+send_check = zeros(Int, nsends)
+recv_check = zeros(Int, nsends)
+
+@sync for i = 1:nsends
+    Threads.@spawn begin
+        recv_req = MPI.Irecv!(recv_arr[i], MPI.COMM_WORLD; source=myrank, tag=i)
+        wait(recv_req)
+        @test MPI.isnull(recv_req)
+        recv_check[i] += 1
+    end
+    Threads.@spawn begin
+        send_req = MPI.Isend(send_arr[i], MPI.COMM_WORLD; dest=myrank, tag=i)
+        wait(send_req)
+        @test MPI.isnull(send_req)
+        send_check[i] += 1
+    end
+end
+
+@test recv_check == ones(Int, nsends)
+@test send_check == ones(Int, nsends)
+
+MPI.Barrier(MPI.COMM_WORLD)
+MPI.Finalize()
+@test MPI.Finalized()