matlab - Using struct arrays in parfor -

i having trouble using struct arrays in matlab's parfor loop. following code has 2 problems not understand:

s=struct('a',{},'b',{}); if matlabpool('size')==0   matlabpool open local 2 end  j = 1:2         parfor k=1:4     fprintf('[%d,%d]\n',k,j)     s(j,k).a = k;     s(j,k).b = j;   end end matlabpool close 

1. it fails error error using parallel_function (line 589) insufficient number of outputs right hand side of equal sign satisfy assignment.
2. on output, variable s vector, not array (as should be, if code breaks before finishing).

edit problem solved if initialize struct arrays correct size, by:

s=struct('a',cell(2,4),'b',cell(2,4)); 

however, still happy insights problem (e.g rally bug, suggested oleg komarov)

it working fine me don't know happens. in general need careful parfor loops , there ample documentation on how align everything. 2 different words of advice. first , more importantly, parfor loop on outside loop:

function s = foo s=struct('a',{},'b',{});  parfor j = 1:2         k=1:4     fprintf('[%d,%d]\n',k,j)     s(j,k).a = k;     s(j,k).b = j;   end end 

two, matlab gets picky writing main exit variable (i.e. variable contained in parfor loop indexed loop, in case, s). first want create dummy variable holds innerloop information, , writes once @ end of loops. example:

function s = khal s=struct('a',{},'b',{});   parfor j = 1:2     dummy=struct('a',{},'b',{});   k=1:4     fprintf('[%d,%d]\n',k,j)     dummy(k).a = k;     dummy(k).b = j;   end   s(j,:) = dummy; end 

you don't have problem here, can complicated in other instances