selectIteratorFunction.m

%% Select the appropriate version of the time iteration function.  Different
%  compiled MEX versions exist for common array sizes, and an uncompiled version
%  is used for anything else.  For now, the Mac computers get the uncompiled
%  code, but if we create compiled versions they can be inserted here.
function handle =  selectIteratorFunction(times, corals, arch)
    % "select" is the length of the time array, which is a proxy for
    % several other array sizes passed into the function.
    % Comments show the original case the code was compiled for, but any
    % case with the same array sizes is a match.
    
    sourceFile1 = dir('timeIteration.m');
    sourceDate1 = sourceFile1.datenum;
    sourceFile2 = dir('Runge_Kutta_2.m');
    sourceDate2 = sourceFile2.datenum;
    if strcmp(arch, 'Mac'); times = 0; end  % Kludge so Macs work without compiled code.
    switch times
        case 23040
            % 1861 to 2100, dt = 0.125
            if corals == 2
                handle = @timeIteration_23040_2_mex;
                mexName = 'timeIteration_23040_2_mex';
            elseif corals == 4
                handle = @timeIteration_23040_4_mex;
                mexName = 'timeIteration_23040_4_mex';
            else
                error('No iterator function for 23040, %d', corals);
            end
        case 38400
            % control400, dt = 0.125
            handle = @timeIteration_38400_mex;
            mexName = 'timeIteration_38400_mex';
        case 19200
            % conrol400, dt = 0.25.
            handle = @timeIteration_400yr_mex;
            mexName = 'timeIteration_400yr_mex';
        case 11520
            % 1861 to 2100, dt = 0.25
            handle = @timeIteration_2100_mex;
            mexName = 'timeIteration_2100_mex';
        case 46080
            % 1861 to 2100, dt = 0.0625
            handle = @timeIteration_46080_mex;
            mexName = 'timeIteration_45080_mex';
        otherwise
            % No MEX file for this case, run the slow way.
            disp('Running with uncompiled iterator function.');
            handle = @timeIteration;
            mexName = '';
    end
  
    %
    % NOTE: If the underlying files are edited for debugging, the timestamp
    % gets updated and the mex files won't be used.  This is good for
    % debugging, but bad when you go back to normal.  A Git reversion does
    % NOT roll back the timestamp.  To do that in windows you can use
    % powershell from a command prompt and then something like this:
    % $(Get-Item .\Runge_Kutta_2_min0_160914.m).lastwritetime=$(Get-Date "8/8/2017 11:01 am")
    %
    if ~isempty(mexName)
        mexFile = dir(strcat(mexName,'.mexw64'));
        if isempty(mexFile)
            disp('Warning: expected compiled version not found.  Using uncompiled timeIteration.m');
            handle = @timeIteration;
        else
            mexDate = mexFile.datenum; 
            if (mexDate < sourceDate1) || (mexDate < sourceDate2)
                fprintf('Warning: timeIteration has not been recompiled to %s.  Using slower uncompiled version.', mexName);
                handle = @timeIteration;
            end
        end
    end
    
end