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:     0.261989 sec
        GraphBLAS time: 0.272427 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    0.349314 sec
        Speedup of GraphBLAS over MATLAB: 1.28223
        check time:     0.260897 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:     0.319877 sec
        GraphBLAS time: 0.333537 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    0.345186 sec
        Speedup of GraphBLAS over MATLAB: 1.03493
        check time:     0.297323 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:     0.356083 sec
        GraphBLAS time: 0.391448 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    187.06 sec
        Speedup of GraphBLAS over MATLAB: 477.866
        check time:     0.292156 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:     0.40299 sec
        GraphBLAS time: 0.446623 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    199.164 sec
        Speedup of GraphBLAS over MATLAB: 445.934
        check time:     0.492775 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:     0.464605 sec
        GraphBLAS time: 0.395374 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    230.122 sec
        Speedup of GraphBLAS over MATLAB: 582.036
        check time:     0.369713 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:     0.510898 sec
        GraphBLAS time: 0.681213 sec
        Starting MATLAB ... please wait ...
        MATLAB time:    251.809 sec
        Speedup of GraphBLAS over MATLAB: 369.649
        check time:     0.416664 sec
        all tests passed