error using parallel.p​ool.consta​nt/get value

1. so this is my code (not sure about function handle in parfeval). The error I get is on line 11. I dont understand the error

poolobj=parpool('my_cluster',8);
[up, op]=ndgri(1e-3:1e-2:1,1e-3:1e-2:1);
up=reshape(up, [1,size(up,1)*size(up,2)]);
up=reshape(up, [1,size(up,1)*size(up,2)]);
z=rand(5,5e3);
addAttachedFiles('<path to my function/cores_random.m');%%to add the function files to workers on the pool
C1=parallel.pool.Constant(z);%%use parallel.pool.Constant to copy these variables into workers
U2=parallel.pool.Constant(up);
O2=parallel.pool.Constant(op);

for i=1:size(up,2)
f1(i)=parfeval(poolobj,@cores_random,3,U2.value(i),O2.Value(i),C1.Value(1,:)); %%line 11
f2(i)=parfeval(poolobj,@cores_random,3,U2.value(i),O2.Value(i),C1.Value(2,:));
f3(i)=parfeval(poolobj,@cores_random,3,U2.value(i),O2.Value(i),C1.Value(3,:));
f4(i)=parfeval(poolobj,@cores_random,3,U2.value(i),O2.Value(i),C1.Value(4,:));
f5(i)=parfeval(poolobj,@cores_random,3,U2.value(i),O2.Value(i),C1.Value(5,:));
end 

for j=1:size(up,2):-1:1
    [idx1,u1,o1,ep1]=fetchNext(f1);
    [idx2,u2,o2,ep2]=fetchNext(f2);
    [idx3,u3,o3,ep3]=fetchNext(f3);
     [idx4,u4,o4,ep4]=fetchNext(f4);
     [idx5,u5,o5,ep5]=fetchNext(f5);
end

I got an error

{Error using paralle.pool.Constant/get.Value The value of a parallel.pool.Constant is only available on the workers. 
Error in main_parallel_norm (line 11) 
f1(i)=parfeval(poolobj,@cores_random,3,U2.value(i),O2.Value(i),C1.Value(1,:));

the function cores_random is as the following:

[uu,oo,ep]=cores_random(up,op,z)
%%doing some calculations here
%%z is of size 1*1e3 
%%up is scalar op is scalar 
end

[Walter Roberson]

Is there a particular reason to ask for 8 cores but use cycles of 5 futures?

[Muna Tageldin]

yes since the output depends on differnt rows of C1.value

On other words the original function is like this:

for i=1:size(up,2)
[u1(1,i),oo(1,i),ep(1,i)]=cores_random(up(i),op(i),z(1,:))
[u1(2,i),oo(2,i),ep(2,i)]=cores_random(up(i),op(i),z(2,:))
[u1(3,i),oo(3,i),ep(3,i)]=cores_random(up(i),op(i),z(3,:))
end

Answer 1

[Walter Roberson]

poolobj=parpool('my_cluster',8);
[up, op]=ndgri(1e-3:1e-2:1,1e-3:1e-2:1);
up=reshape(up, [1,size(up,1)*size(up,2)]);
up=reshape(up, [1,size(up,1)*size(up,2)]);
z=rand(5,5e3);
addAttachedFiles('<path to my function/cores_random.m');%%to add the function files to workers on the pool
C1=parallel.pool.Constant(z);%%use parallel.pool.Constant to copy these variables into workers
U2=parallel.pool.Constant(up);
O2=parallel.pool.Constant(op);

for i=1:size(up,2)
    f1(i) = parfeval(poolobj,@cores_random, 2, i, 1); %%line 11
    f2(i) = parfeval(poolobj,@cores_random, 2, i, 2);
    f3(i) = parfeval(poolobj,@cores_random, 2, i, 3);
    f4(i) = parfeval(poolobj,@cores_random, 2, i, 4);
    f5(i) = parfeval(poolobj,@cores_random, 2, i, 5);
end 

for j=1:size(up,2):-1:1
    [idx1,u1,o1,ep1]=fetchNext(f1);
    [idx2,u2,o2,ep2]=fetchNext(f2);
    [idx3,u3,o3,ep3]=fetchNext(f3);
     [idx4,u4,o4,ep4]=fetchNext(f4);
     [idx5,u5,o5,ep5]=fetchNext(f5);
end

function [uu,oo,ep] = cores_random(i, zidx)
    up = U2.Value(i)
    op = O2.Value(i);
    z = C1.Value(zidx,:);
    
    %%doing some calculations here
    %%z is of size 1*1e3 
    %%up is scalar op is scalar 
end

[Muna Tageldin]

why would I pass the indices to the function instead of the data themselves? . I will try it. Thanks

[Walter Roberson]

parpool constant sends the entire variable to the workers. The data is already on the workers, so you do not need to send the data again, just the index to use.

[Muna Tageldin]

ok thanks actually it worked but I have changed 2 to 3 since I am having 3 ouputs

f1(i) = parfeval(poolobj,@cores_random, 2, i, 1);

[Muna Tageldin]

Also, when I run the matlab code, I got an error:

"The parallel pool has shutwodn" and when I examined the log file I get the following:

f3= 1*2 FevalFuture array

ID State FinishedDateTime function Error

8 finished(unread) @cores_random Error

Not really sure where this error come from

[Walter Roberson]

Are you getting any succesful outputs ?

[Muna Tageldin]

no output