dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

ok, thanks. I think I got it now...

/Anders

On Tue, Jun 14, 2005 at 05:56:52PM -0500, Matthew Knepley wrote:
> Anders Logg <logg@xxxxxxxxx> writes:
> 
> > I'm a little confused...
> >
> > Matt says:
> >
> >    This flag says:
> >  
> >    1) You configured with --with-clanguage=C++ so that the C++
> >    compiler is used to compile the libraries.
> >
> > Barry says:
> >
> >     If PETSc is configured to compile with the C++ compiler
> >     --with-clanguage=c++ then this flag should NOT be used
> >
> > Which is it?
> 
>   We both say that using this flag is not recommended. It does have the effect
> of demangling the PETSc symbols.
> 
> > Which is the default? If I just do
> >
> >     ./config/configure.py
> >     make BOPT=g_c++
> >     make BOPT=O_c++
> >
> > then I should not need this flag, right?
> >
> 
>         Yes.
> 
> > If someone needs it, that means he (Andy) did something different when
> > compiling PETSc?
> 
>   Yes, that means he wants to call a C++ PETSc from C code.
> 
>        Matt
> 
> > /Anders
> >
> > On Tue, Jun 14, 2005 at 02:49:37PM -0500, Matthew Knepley wrote:
> >> Anders Logg <logg@xxxxxxxxx> writes:
> >> 
> >>        This flag says:
> >> 
> >>   1) You configured with --with-clanguage=C++ so that the C++ compiler is used to
> >>      compile the libraries.
> >> 
> >>   2) The PETSc symbols are NOT mangled when using PETSC_USE_EXTERN_CXX so C code
> >>      can call these symbols.
> >> 
> >> This is not are normal mode. We believe if you want to compile with C++, then you
> >> want mangled symbols.
> >> 
> >>      Thanks,
> >> 
> >>         Matt
> >> 
> >> > I think we added a
> >> >
> >> > PETSC_CFLAGS="$PETSC_CFLAGS -DPETSC_USE_EXTERN_CXX"
> >> >
> >> > just below the definition of PETSC_CFLAGS in configure.ac.  You need
> >> > to add this, then run scripts/preconfigure and then ./configure again.
> >> >
> >> > We get PETSC_CFLAGS by
> >> >
> >> > PETSC_CFLAGS=`make -s -C $PETSC_DIR getincludedirs PETSC_DIR=$PETSC_DIR BOPT=$BOPT`
> >> >
> >> > which I think should be enough. I don't know why the extra
> >> > -DPETSC_USE_EXTERN_CXX helps on some systems or why it's not included
> >> > with getincludedirs.
> >> >
> >> > /Anders
> >> >
> >> > On Tue, Jun 14, 2005 at 01:38:05PM -0500, Andy Ray Terrel wrote:
> >> >> Sorry to bother you again.  But when I tried to run some things with 
> >> >> dolfin I just got a PETSc Error.  So I tried to rebuild but remembered 
> >> >> that when I built the first time I had to add some linker to PETSc 
> >> >> somewhere.  Well I have forgotten what it was we added to get PETSc to 
> >> >> link.  Do you remember?
> >> >> 
> >> >> Andy
> >> >> 
> >> >> Anders Logg wrote:
> >> >> 
> >> >> >You need to do A and B separately, as two different forms in two
> >> >> >different files.
> >> >> >
> >> >> >In the first file, do something like
> >> >> >
> >> >> >   vector = FiniteElement("Vector Lagrange", "triangle", 1)
> >> >> >
> >> >> >   v = BasisFunction(vector)
> >> >> >   u = BasisFunction(vector)
> >> >> >
> >> >> >   a = v.dx(i)*u.dx(i)*dx
> >> >> >
> >> >> >In the second file, do something like
> >> >> >
> >> >> >   vector = FiniteElement("Vector Lagrange", "triangle", 1)
> >> >> >   scalar = FiniteElement("Lagrange", "triangle", 1)
> >> >> >   
> >> >> >   q = BasisFunction(scalar)
> >> >> >   u = BasisFunction(vector)
> >> >> >
> >> >> >   a = q*u[i].dx(i)*dx
> >> >> >
> >> >> >Compile each form and then assemble separately in DOLFIN to get A and B.
> >> >> >You can then either combine A and B to get the full matrix, or you can
> >> >> >do fixed-point iteration, or you can create something called a
> >> >> >"VirtualMatrix" in DOLFIN which implements the matrix-vector product
> >> >> >for the full matrix in terms of A and B.
> >> >> >
> >> >> >Hope this helps. Ask me again when you need more help.
> >> >> >
> >> >> >/Anders
> >> >> >
> >> >> >On Tue, Jun 14, 2005 at 09:48:43AM -0500, Andy Terrel wrote:
> >> >> > 
> >> >> >
> >> >> >>Hey Anders,
> >> >> >>
> >> >> >>I am having some trouble figuring out how to write some stokes equations 
> >> >> >>up for my project.  So I have the forms:
> >> >> >>
> >> >> >>a = v.dx(j) *u.dy(j)
> >> >> >>b= q*r*dx
> >> >> >>
> >> >> >>and I want to construct the matrix C s.t.
> >> >> >>   [ A   B^t  ]
> >> >> >>C=[ B    0     ]
> >> >> >>
> >> >> >>This is so I can call some mixed methods for the solving of the problem 
> >> >> >>to get the benchmarking results.
> >> >> >>
> >> >> >>If you have time can you help me?
> >> >> >>
> >> >> >>Andy
> >> >> >>
> >> >> >>PS This is to solve (grad(u), grad(v)) - (p, div(v)) = 0,
> >> >> >>                           (div(u), w) = 0.
> >> >> >>
> >> >> >>   
> >> >> >>
> >> >> >
> >> >> > 
> >> >> >
> >> >> 
> >> >
> >> >
> >> >
> >> >
> >> 
> >
> >
> >
> >
> 

-- 
Anders Logg
Research Assistant Professor
Toyota Technological Institute at Chicago
http://www.tti-c.org/logg/