about parfor with reading from cell array ????

hello everyone i use the following code to do some operation (maxflow) for each element of cell array, each element contains 3*n array which represent a graph. the achieved speed up is not logical any suggestions? the code :

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parpool(4);

c = parallel.pool.Constant(sss0);

 tm00=tic;
 parfor i=1:1:size(sss0,2)
   maxflows((c.Value{1,i}(1,:)),(c.Value{1,i}(2,:)),(c.Value{1,i}(3,:)),source,sink);  

 end
tm01=toc(tm00)

[Sergey Kasyanov]

Can you attache maxflows function? What is source and sink?

[abdullah alzaqebah]

function mf=maxflows(s,t,weights,source,sink);

[u, ~, w] = unique([s t]);

G1=digraph(w(1:end/2), w(end/2+1:end), weights, cellstr(num2str(u.')));

k=num2str(source(1,2));

k2=num2str(sink(1,2));

f=table2array(G1.Nodes(:,:));

f=strrep(f,' ','');

idx = all(ismember(f,k),2);

idx1 = all(ismember(f,k2),2);

id=find(idx==1);

ids=find(idx1==1);

mf = maxflow(G1,id,ids,'augmentpath');

[abdullah alzaqebah]

source and sink represnt the source node and the target node in the graph which already inside the array but pass it to construct the graph inside the function

[abdullah alzaqebah]

sss0 contains 4 cells

1- 3*210

2- 3* 2628

3- 3*389403

4- 3*406

time taken on one worker is 24.2647

time taken on 4 workers is 21.9487

which is not logical!