Merge pull request #539 from JuliaParallel/jps/datadeps-gpu-fixes

Minor fixes to Datadeps for GPUs

src/array/cholesky.jl

@@ -2,7 +2,7 @@ LinearAlgebra.cholcopy(A::DArray{T,2}) where T = copy(A)
 function potrf_checked!(uplo, A, info_arr)
     _A, info = move(thunk_processor(), LAPACK.potrf!)(uplo, A)
     if info != 0
-        info_arr[1] = info
+        fill!(info_arr, info)
         throw(PosDefException(info))
     end
     return _A, info

src/datadeps.jl

@@ -450,7 +450,13 @@ function distribute_tasks!(queue::DataDepsTaskQueue)
     filter!(proc->!isa(constrain(ExactScope(proc), scope),
                        InvalidScope),
             all_procs)
+    if isempty(all_procs)
+        throw(Sch.SchedulingException("No processors available, try widening scope"))
+    end
     exec_spaces = unique(vcat(map(proc->collect(memory_spaces(proc)), all_procs)...))
+    if !all(space->space isa CPURAMMemorySpace, exec_spaces) && !all(space->root_worker_id(space) == myid(), exec_spaces)
+        @warn "Datadeps support for multi-GPU, multi-worker is currently broken\nPlease be prepared for incorrect results or errors" maxlog=1
+    end
 
     # Round-robin assign tasks to processors
     upper_queue = get_options(:task_queue)