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: 8

    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:     0.412634 sec
        GraphBLAS time: 1.19528 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    0.507453 sec
        Speedup of GraphBLAS over MATLAB: 0.424546
        check time:     0.570694 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:     0.859294 sec
        GraphBLAS time: 1.13881 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    0.489687 sec
        Speedup of GraphBLAS over MATLAB: 0.429997
        check time:     0.591902 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:     0.800442 sec
        GraphBLAS time: 1.17931 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    155.789 sec
        Speedup of GraphBLAS over MATLAB: 132.102
        check time:     0.65189 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:     0.902976 sec
        GraphBLAS time: 1.55605 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    168.386 sec
        Speedup of GraphBLAS over MATLAB: 108.213
        check time:     0.658529 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:     1.0054 sec
        GraphBLAS time: 1.24475 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    187.577 sec
        Speedup of GraphBLAS over MATLAB: 150.694
        check time:     0.783732 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:     1.11575 sec
        GraphBLAS time: 1.68189 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    208.664 sec
        Speedup of GraphBLAS over MATLAB: 124.065
        check time:     0.839128 sec
        all tests passed