Build error | resizing a vector of FunctionParsers

[vachanpo...@gmail.com]

Dear all,

I require to use a vector of an array of FunctionParsers in my code

std::vector< std::array<FunctionParser<2>, 4> > fps_vec;

At a later point when I know its size, I call

fps_vec.resize(size);

This line produces a long build error message (attached) starting with

invalid application of ‘sizeof’ to incomplete type ‘mu::Parser’
  static_assert(sizeof(_Tp)>0,

If I comment out the resize line, then the remaining program compiles successfully. I noted that such an error occurs when the compiler is not able to see the object's declaration. But I already included the header file deal.II/base/function_parser.h. Wouldn't that point to relevant muparser's header file?

In a different file, I had used an std array of FunctionParsers and that worked fine. Doesn't that mean that the definition of mu::Parser is visible to compiler? I am unable to understand what is causing this error.

Is there any workaround for this? Thanks in advance!

[Wells, David]

Hi Vachan,

We explicitly disabled copying and moving instances of FunctionParser because it depends (for threaded parallelism) on several objects that cannot be copied or moved - that's why your code works as long as you don't try to resize the vector. The best workaround is to use

std::vector<std::unique_ptr<std::array<FunctionParser<2>, 4>>

(or switch the order of unique pointer and the array - what matters is that we move pointers instead of FunctionParser instances) so that no copies or moves are required.

Best,

David

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From: dea...@googlegroups.com <dea...@googlegroups.com> on behalf of vachanpo...@gmail.com <vachanpo...@gmail.com>
Sent: Wednesday, January 13, 2021 1:23 AM
To: deal.II User Group <dea...@googlegroups.com>
Subject: [deal.II] Build error | resizing a vector of FunctionParsers

 

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[vachanpo...@gmail.com]

Thanks a lot David! This works!