graphblas_demo2
Date: 2020-06-25

    % Run the GraphBLAS demo2

    % SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2020, All Rights Reserved.
    % http://suitesparse.com   See GraphBLAS/Doc/License.txt for license.

    gbdemo2

     GBDEMO2 Extreme performance differences: GraphBLAS vs MATLAB.

      Usage:

            gbdemo2             % uses a default bnz = 6000
            gbdemo2 (20000)     % uses bnz = 20000

      The GraphBLAS operations used in gbdemo are perhaps 3x to 50x
      faster than the corresponding MATLAB operations, depending on how
      many cores your computer has.  Here's an example where GraphBLAS is
      asymptotically far faster than MATLAB R2019a: a simple assignment
      for a large matrix C:

            C(I,J) = A

      The matrix C is constructed via C = kron (B,B) where nnz (B) is
      roughly the bnz provided on input (with a default of bnz = 6000),
      so that C will have about bnz^2 entries, or 36 million by default.
      I and J are chosen randomly, and A is 5000-by-5000.

      When the problem becomes large, MATLAB will take a very long time.
      If you have enough memory, and want to see higher speedups in
      GraphBLAS, increase bnz (and be prepared to wait even longer).
      With the default bnz = 6000, this test takes about 4GB of RAM.

      On my Dell XPS 4-core laptop (Intel(R) Core(TM) i7-8565U, 16GB
      RAM), using MATLAB R2019a, when C becomes 9 million by 9 million,
      the computation C(I,J)=A for MATLAB matrices C, I, J, and A takes
      several minutes, whereas GraphBLAS takes less than a second, or
      about 500x faster than MATLAB.  On a desktop with an Intel(R)
      Xeon(R) CPU E5-2698 v4 @ 2.20GHz with 20 hardware cores, the
      speedup over MATLAB is even more dramatic (up to 2,660x has been
      observed).

      See also GrB.assign, subsasgn.

    # of threads used in GraphBLAS: 20

    C(I,J)=A where C is 1 million -by- 1 million
    with 35.7126 million entries:

        A is 5000-by-5000 with 49954 entries
        setup time:     0.329855 sec
        GraphBLAS time: 0.173019 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    0.474924 sec
        Speedup of GraphBLAS over MATLAB: 2.74492
        check time:     0.215864 sec
        all tests passed

    C(I,J)=A where C is 4 million -by- 4 million
    with 35.8202 million entries:

        A is 5000-by-5000 with 49954 entries
        setup time:     0.417582 sec
        GraphBLAS time: 0.203017 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    0.453103 sec
        Speedup of GraphBLAS over MATLAB: 2.23185
        check time:     0.22641 sec
        all tests passed

    C(I,J)=A where C is 9 million -by- 9 million
    with 35.928 million entries:

        A is 5000-by-5000 with 49954 entries
        setup time:     0.485024 sec
        GraphBLAS time: 0.249401 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    228.188 sec
        Speedup of GraphBLAS over MATLAB: 914.945
        check time:     0.249945 sec
        all tests passed

    C(I,J)=A where C is 16 million -by- 16 million
    with 35.916 million entries:

        A is 5000-by-5000 with 49954 entries
        setup time:     0.552762 sec
        GraphBLAS time: 0.292017 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    246.474 sec
        Speedup of GraphBLAS over MATLAB: 844.041
        check time:     0.27686 sec
        all tests passed

    C(I,J)=A where C is 25 million -by- 25 million
    with 35.964 million entries:

        A is 5000-by-5000 with 49954 entries
        setup time:     0.630048 sec
        GraphBLAS time: 0.25246 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    269.415 sec
        Speedup of GraphBLAS over MATLAB: 1067.16
        check time:     0.311659 sec
        all tests passed

    C(I,J)=A where C is 36 million -by- 36 million
    with 35.976 million entries:

        A is 5000-by-5000 with 49954 entries
        setup time:     0.712427 sec
        GraphBLAS time: 0.401151 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    296.906 sec
        Speedup of GraphBLAS over MATLAB: 740.134
        check time:     0.35269 sec
        all tests passed