On 6/24/20 3:14 PM, Krishnakumar Gopalakrishnan wrote:
Hi,
I am solving the basic diffusion equation using the direct method (based on
Step-52).
I have made the following changes from Step-52 tutorial
1. The domain is now 1D (as opposed to 2D in step-52)
2. We have Neumann BCs on both ends (left NeumannBC = 0.5, right NeumannBC= 0)
3. Removes the code for MMS validation (i.e. no source term S(t)) so that we
solve for the unknown field variable, instead of verifying whether the
pre-formulated analytical solution is retrieved)
4. Sets the absorpotion coefficient, Sigma_a = 0
5. Sets a non-zero initial condition (but a spatially constant value).
The C++ source code & Cmakelists.txt files are attached herewith. The solution
is indeed correct and is as expected, and I have visualised this in Paraview.
However, I'd like to understand the compilation warnings.
Some of them have to do with "unused variables", which are somewhat
straightforward to get rid of. But the other warnings which all have the
string "required from here" is not so clear to me.
Read the error/warning message in its entirety. For example, the first one says
/home/bangerth/p/deal.II/1/install/examples/step-1/step-1.cc: In instantiation
of ‘void DiffusionEqn::SolidDiffusion<dim>::run() [with int dim = 1]’:
/home/bangerth/p/deal.II/1/install/examples/step-1/step-1.cc:441:26:
required from here
/home/bangerth/p/deal.II/1/install/examples/step-1/step-1.cc:420:24: warning:
variable ‘n_steps’ set but not used [-Wunused-but-set-variable]
unsigned int n_steps = 0;
^~~~~~~
If you strip the details, it says:
In instantiation of function b() // i.e., while compiling a()
required from here // i.e., we got to a() while compiling b()
warning: variable unused
In other words, the compiler isn't just telling you where (in which function
and line of code) the problem happened, but also *why* it is compiling this
function (because it's called from some other place) and with which template
arguments.
Best
W.
Can someone please explain what these warnings mean, and what is the best
practice for refactoring it to avoid such warnings.
Thanks!
Krishna
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