Integration using GPU computing

I have a problem that requires nesting integrals and I cannot use double or triple integrals as it is extremely difficult with the math. To speed the process, I am doing the integrals on the GPU using trapz. But, when I run it, I consistently get the error:

Error using gpuArray/arrayfun Indexing is not supported.

I am not entirely sure what to do.

Here is the section of code I am having the problems with

        function val_L1=L1_int(g)
            val_L1= 1./4.*mu0.*pi.^2.*N_drive.^2.*(-StruveH(1,OR_drive.*g).*besselj(0,OR_drive.*g).*OR_drive+besselj(1,OR_drive.*g).*StruveH(0,OR_drive.*g).*OR_drive-besselj(1,IR_drive.*g).*StruveH(0,IR_drive.*g).*IR_drive+besselj(0,IR_drive.*g).*StruveH(1,IR_drive.*g).*IR_drive).^2 .*(g.*H_drive.*exp(g.*H_drive)-exp(g.*H_drive)+1).*exp(-g.*H_drive)./H_drive.^2./g.^4./(IR_drive-OR_drive).^2;
            function Z=StruveH(p,z)
                int_arr= gpuArray.linspace(0, pi/2, N);
                intVecSpacing = (pi/2 - 0)/N;
                F = arrayfun(@StruveIntegrand, int_arr);
                Z = trapz(F) * intVecSpacing;
                function integrand=StruveIntegrand(t)
                    integrand=(2.*(z./2).^p)./(sqrt(pi).*gamma(p+0.5)).*sin(z.*cos(t)).*(sin(t)).^(2.*p);
                end
            end  
        end
    Ld=2*pi*trapz1(@L1_int,1e-8,2.5e3,N)

The integration being used in simple trapz:

function Z = trapz1(func, xmin, xmax, N)
xvals = gpuArray.linspace(xmin, xmax, N);
xspacing = (xmax - xmin)/N;
F=arrayfun(func,xvals);
Z=trapz(F)*xspacing;
end

I am using Matlab 2014b to do these computations.

[Joss Knight]

Please write your code so I can run it. At the moment certain essential variables are missing such as mu0 and N_drive, and certain functions are missing such as StruveH.

The error message means that you can't index into arrays inside a GPU arrayfun function because of its special behaviour. The only circumstance under which indexing is allowed is if the indexing is into an upvalue, and if it returns a scalar.