Distributed computations

This section of the manual describes functions to make use of distributed computation.

• Distributed computations
• Using multiple threads

Using multiple threads

To control the number of threads used by your BLAS library, use the function Base.LinAlg.BLAS.set_num_threads(n), where n is an integer. Furthermore, the function get_num_threads() defined below will return the current value.

Note. If you are using Julia v"0.7-" (run the command VERSION to find this), instead of Base.LinAlg below use LinearAlgebra, and this module should have been loaded in the current scope with using LinearAlgebra.

#
# This function is a part of Julia. License is MIT: https://julialang.org/license
#
function get_num_threads() # anonymous so it will be serialized when called
    blas = Base.LinAlg.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 ENV["VECLIB_MAXIMUM_THREADS"]
        end
    end

    return nothing
end