function PAPIMatrixVector

% Compute a Matrix Vector multiply 

% on arrays and vectors sized from 50 to 500,

% in steps of 50. 

%

% Use the PAPI mex function with two different methods:

% - The PAPI High Level flops call

% - PAPI High Level start/stop calls

%

% For each size, display:

% - number of floating point operations

% - theoretical number of operations

% - difference

% - per cent error

% - mflops/s

fprintf(1,'\nPAPI Matrix Vector Multiply Test');

fprintf(1,'\nUsing the High Level PAPI("flops") call');

fprintf(1,'\n%12s %12s %12s %12s %12s %12s\n', 'n', 'ops', '2n^2', 'difference', '% error', 'mflops')

for n=50:50:500,

    a=rand(n);x=rand(n,1);

    PAPI('stop'); % reset the counters to zero

    PAPI('flops'); % start counting flops

    b=a*x;

    [count, mflops] = PAPI('flops'); % read the flops data

    fprintf(1,'%12d %12d %12d %12d %12.2f %12.2f\n',n,count,2*n^2,count - 2*n^2, (1.0 - ((2*n^2) / count)) * 100,mflops)

end

PAPI('stop');

fprintf(1,'\nPAPI Matrix Vector Multiply Test');

fprintf(1,'\nUsing PAPI start and stop');

fprintf(1,'\n%12s %12s %12s %12s %12s %12s\n', 'n', 'ops', '2n^2', 'difference', '% error', 'flops/cycle')

for n=50:50:500,

    a=rand(n);x=rand(n,1);

    PAPI('start', 'PAPI_TOT_CYC', 'PAPI_FP_OPS');

    c=a*x;

    [cyc, ops] = PAPI('stop');

    fprintf(1,'%12d %12d %12d %12d %12.2f %12.6f\n',n,ops,2*n^2,ops - 2*n^2, (1.0 - ((2*n^2) / ops)) * 100,ops/cyc)

end