Output argument "isBdNode" (and possibly others) not assigned a value in the execution with "gradmatrix" function.

[litaihe]

when I run the example\fem\Maxwell\Maxwell3ND0femrate.m, the fellowing error will appear

Output argument "isBdNode" (and possibly others) not assigned a value in
the execution with "gradmatrix" function.

Error in mgMaxwell (line 79)
[grad,isBdNode] = gradmatrix(edge,isBdEdge);

Error in Maxwell (line 393)
    [u,info] = mgMaxwell(bigAD,f,AP,node,elemold,edge,HB,option);

Error in femMaxwell3 (line 60)
                [u,edge,eqn,info] = Maxwell(node,elem,bdFlag,pde,option);

Error in Maxwell3ND0femrate (line 39)
femMaxwell3(mesh,pde,option);

this error will be resolved when I make the following changes to the file solver/gradmatrix.m

@@ -28,5 +28,6 @@ if any(isBdEdge) % no grad on boundary edges
    idx = ~(isBdEdge(i) | isBdNode(j)); 
else
    idx = 1:length(i);
    isBdNode = false(N,1);
end
grad = sparse(i(idx),j(idx),s(idx),NE,N);

is the modification reasonable? thank you.

[scaomath]

Your fix is technically correct, since the Neumann type BC counts the ND0 bases' coeffs on boundary edges as DoF (not fixed values), there is no BdNode (fixed valued nodes) and all the nodes on the boundary should go into the transfer matrix.

However, a better coding practice is to set isBdNode outside the if-else conditionals in front of the lines 24

https://github.com/lyc102/ifem/blob/29f31c812001ca8d93dad08e67208ca60e8716d4/solver/gradmatrix.m#L24-L31

Please submit a PR to fix this following my suggestion, is possible, please include your university/advisor and what project you are currently working on using ifem.

[scaomath]

Fixed in #12