Changing the size of SPMD

I need to close spmd and open another spmd of a smaller size repeatedly, but I receive this error that there exists an active spmd. I need to open and close spmds in a loop. What I am actually doing to get my code working is closing and opening the pool every time at the beginning of the loop, which is really inefficient. Also, I am using 2012b and it does not recognize "delete(gcp)".

I would appreciate your help!

[Mehdi]

This is a kind of emergency for me! Here is the loop that I use SPMD in it. As you see I have cleared all the composite, yet the same error:

for io=1:Q+1
      display(['io = ' num2str(io)]);
  %     matlabpool close 

        N_spmdOld=N_spmd; 
        if io==Q+1 
            N_spmd=R; 
        end

        spmd (N_spmd)
            ak=xi((io-1)*N_spmdOld+labindex);
            bk=xi((io-1)*N_spmdOld+labindex+1);
            K1=(bk-ak)/2; 
            K2=(bk+ak)/2;

            Cijk_E=CPU_gPCCijk(M,p_E,Type); 
            PSI2Norm_E=CPU_Psi2Norm(M,p_E,Type); 
            A_E=K1*Cijk_E{2}+K2*Cijk_E{1};
            for i=1:Size_E
                A_E(i,:)=-A_E(i,:)/PSI2Norm_E(i);
            end
        end

        odefun_E=Composite();
        for k=1:N_spmd
            B_E=A_E{k}; 
            odefun_E{k}=@(t,u)(B_E*u);
        end

        spmd (N_spmd)

            u0_E=zeros(Size_E,1);
            u0_E(1)=U0; 
            options = odeset('MaxStep',(tn-t0)/(numt));
            [~,U_E]=ode45(odefun_E,T,u0_E,options); 

            MeanE=U_E(:,1); 
            VarE=zeros(numt,1);
            for i=1:numt
                sum=0;
                for j=2:Size_E
                    sum=sum+PSI2Norm_E(j)*U_E(i,j)^2;
                end
                VarE(i)=sum;
            end

        end

        for k=1:N_spmd
            MeanME=MeanME+MeanE{k};
        end   
        for k=1:N_spmd
            s=s+1;
            UE=U_E{k}; 
            UEsaved(:,s)=UE(:,1);
        end
        for k=1:N_spmd
            VarME=VarME+VarE{k};
        end

        clear labindex ak bk K1 K2 Cijk_E PSI2Norm_E A_E B_E odefun_E u0_E options U_E sum MeanE VarE i j k
    end

Answer 1

[Edric Ellis]

You probably have existing distributed arrays or Composite objects in your workspace - these prevent you from changing the size of the active SPMD context. If you clear all those from your workspace, you should be able to proceed.

[Mehdi]

I have Composite objects, but is there any way to delete all the composite objects at the same time (in case there are too many of them). Is there any way to delete spmd and open it again without closing the pool?

[Mehdi]

I tried to clear the composite variables (using "clear variable names" in the loop), but it didn't help and I am still receiving the same error:

Error using spmdlang.ResourceSetMgr.chooseResourceSet (line 255)
Could not create an SPMD block to match the requested size: 3. The matlabpool size is: 12, the active SPMD context is of size: 12.

[micholeodon]

https://www.alecjacobson.com/weblog/?p=2608

Here you can find a way to clear all Composites in your workspace.

Edit Rik:

The contents of that page show this solution:

D = whos();
D = D(arrayfun(@(d) strcmp(d.class,'yourclassname'),D));
clear(D.name)

[micholeodon]

Also avoid syntax with tildas like:

[outvar1, ~] = some_function(arg1, arg2);      

do instead

outvar1 = some_function(arg1, arg2);  

because it can trigger context error as well.