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savefaststruct.m : savefast a structure (works inside parfor)
function savefaststruct(filename, savestruct)
% savefaststruct: fast saves of large arrays to .mat files
%
% Matlab's 'save' command can be very slow when saving large arrays,
% because by default Matlab attempts to use compression. This function
% provides a much faster alternative, at the cost of larger files.
%
% 'savefaststruct' version saves variables from a structure
% this avoids the need for evalin which does not work inside
% parfor etc.
% Copyright 2013 by Timothy E. Holy
% Extract the variable values
varnames = fieldnames(savestruct);
vars = cell(size(varnames));
for i = 1:numel(vars)
vars{i} = savestruct.(varnames{i})
end
% Separate numeric arrays from the rest
isnum = cellfun(@(x) isa(x, 'numeric'), vars);
% Append .mat if necessary
[filepath, filebase, ext] = fileparts(filename);
if isempty(ext)
filename = fullfile(filepath, [filebase '.mat']);
end
create_dummy = false;
if all(isnum)
% Save a dummy variable, just to create the file
dummy = 0; %#ok<NASGU>
save(filename, '-v7.3', 'dummy');
create_dummy = true;
else
s = struct;
for i = 1:numel(isnum)
if ~isnum(i)
s.(varnames{i}) = vars{i};
end
end
save(filename, '-v7.3', '-struct', 's');
end
% Delete the dummy, if necessary, just in case the user supplied a
% variable called dummy
if create_dummy
fid = H5F.open(filename,'H5F_ACC_RDWR','H5P_DEFAULT');
H5L.delete(fid,'dummy','H5P_DEFAULT');
H5F.close(fid);
end
% Save all numeric variables
for i = 1:numel(isnum)
if ~isnum(i)
continue
end
varname = ['/' varnames{i}];
h5create(filename, varname, size(vars{i}), 'DataType', class(vars{i}));
h5write(filename, varname, vars{i});
end
end
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