[WIP] Use libblastrampoline to forward to a user-defined BLAS at runt…

…ime (#39455)

test/distributed_exec.jl

@@ -1005,30 +1005,8 @@ end
 
 # Test addprocs enable_threaded_blas parameter
 
-const get_num_threads = function() # anonymous so it will be serialized when called
-    blas = LinearAlgebra.BLAS.vendor()
-    # Wrap in a try to catch unsupported blas versions
-    try
-        if blas == :openblas
-            return ccall((:openblas_get_num_threads, Base.libblas_name), Cint, ())
-        elseif blas == :openblas64
-            return ccall((:openblas_get_num_threads64_, Base.libblas_name), Cint, ())
-        elseif blas == :mkl
-            return ccall((:MKL_Get_Max_Num_Threads, Base.libblas_name), Cint, ())
-        end
-
-        # OSX BLAS looks at an environment variable
-        if Sys.isapple()
-            return tryparse(Cint, get(ENV, "VECLIB_MAXIMUM_THREADS", "1"))
-        end
-    catch
-    end
-
-    return nothing
-end
-
 function get_remote_num_threads(processes_added)
-    return [remotecall_fetch(get_num_threads, proc_id) for proc_id in processes_added]
+    return [remotecall_fetch(BLAS.get_num_threads, proc_id) for proc_id in processes_added]
 end
 
 function test_blas_config(pid, expected)
@@ -1041,7 +1019,7 @@ function test_blas_config(pid, expected)
 end
 
 function test_add_procs_threaded_blas()
-    master_blas_thread_count = get_num_threads()
+    master_blas_thread_count = BLAS.get_num_threads()
     if master_blas_thread_count === nothing
         @warn "Skipping blas num threads tests due to unsupported blas version"
         return
@@ -1055,7 +1033,7 @@ function test_add_procs_threaded_blas()
     end
 
     # Master thread should not have changed
-    @test get_num_threads() == master_blas_thread_count
+    @test BLAS.get_num_threads() == master_blas_thread_count
 
     # Threading disabled in children by default
     thread_counts_by_process = get_remote_num_threads(processes_added)
@@ -1069,9 +1047,9 @@ function test_add_procs_threaded_blas()
         test_blas_config(proc_id, true)
     end
 
-    @test get_num_threads() == master_blas_thread_count
+    @test BLAS.get_num_threads() == master_blas_thread_count
 
-    # BLAS.set_num_threads(`num`) doesn't  cause get_num_threads to return `num`
+    # BLAS.set_num_threads(`num`) doesn't  cause BLAS.get_num_threads to return `num`
     # depending on the machine, the BLAS version, and BLAS configuration, so
     # we need a very lenient test.
     thread_counts_by_process = get_remote_num_threads(processes_added)