dolfin team mailing list archive

["Dag Lindbo" <dag@xxxxxxxx>]

The code I attach breaks the function. Should be very simple to make, and
understand. main() is in LSM_test.cpp

/Dag

>
> It will take me some time to write a stand-alone code that someone else
> can run, so hang on.
>
> Gdb says:
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread -1208269120 (LWP 12715)]
> 0x004776ed in dolfin::DiscreteFunction::updateVectorDimension ()
>    from /usr/local/lib/libdolfin.so.0
>
>
> Valgrind says the same (I guess):
>
> ==12683== Invalid read of size 4
> ==12683==    at 0x1BA106EA:
> dolfin::DiscreteFunction::updateVectorDimension() (in
> /usr/local/lib/libdolfin.so.0.0.0)
> ==12683==    by 0x1BA10966:
> dolfin::DiscreteFunction::DiscreteFunction(dolfin::uBlasVector&,
> dolfin::Mesh&, dolfin::FiniteElement&) (in
> /usr/local/lib/libdolfin.so.0.0.0)
> ==12683==    by 0x1BA13B30:
> dolfin::Function::Function(dolfin::uBlasVector&, dolfin::Mesh&,
> dolfin::FiniteElement&) (in /usr/local/lib/libdolfin.so.0.0.0)
> ==12683==    by 0x804E1FB:
> dolfin::Vec_Func_fcns::L2_Error_DF_DF(dolfin::Mesh&, dolfin::Function&,
> dolfin::Function&) (Vec_Func_fcns.cpp:41)
> ==12683==    by 0x808F6E6: main (LSM_test.cpp:135)
> ==12683==  Address 0x1BD79D68 is 0 bytes inside a block of size 12 free'd
> ==12683==    at 0x1B9098CF: operator delete(void*)
> (vg_replace_malloc.c:155)
> ==12683==    by 0x804F87D:
> dolfin::Scalar_L2Error::LinearForm::FunctionElement_1::~FunctionElement_1()
> (Scalar_L2Error.h:228)
> ==12683==    by 0x1BA0D703: dolfin::Form::~Form() (in
> /usr/local/lib/libdolfin.so.0.0.0)
> ==12683==    by 0x1BA0FBCA: dolfin::LinearForm::~LinearForm() (in
> /usr/local/lib/libdolfin.so.0.0.0)
> ==12683==    by 0x80539FF:
> dolfin::Scalar_L2Error::LinearForm::~LinearForm() (Scalar_L2Error.h:23)
> ==12683==    by 0x804E52B:
> dolfin::Vec_Func_fcns::L2_Error_Exact(dolfin::Mesh&, dolfin::Function&,
> dolfin::Function&) (Vec_Func_fcns.cpp:29)
> ==12683==    by 0x808F666: main (LSM_test.cpp:131)
> pure virtual method called
> terminate called without an active exception
>
>
>
>> On Sun, Oct 01, 2006 at 06:35:51PM +0200, Dag Lindbo wrote:
>>> Hi all,
>>>
>>> I'm a bit confused about passing a Function to a function and using it
>>> to
>>> assemble some system. What I'm doing is passing a Function, "func", by
>>> reference, to a function, foo, where func goes into a form and that
>>> form
>>> is assembled etc.
>>>
>>> Vector& Another_Class::foo(Mesh& mesh, Function& func)
>>> 	{
>>> 		AAA::BilineraForm a
>>> 		AAA::LinearForm L(func)
>>>
>>> 		FEM:assemble(...)
>>> 		lu_solver.solve(...)
>>>
>>> 		return x;
>>> 	}
>>>
>>> This works fine, but when the context that called foo (e.g. main)
>>> resumes
>>> something has happended to "func". The next time it is referenced the
>>> porgram terminates with a segmentation violation. To get around this I
>>> can
>>> copy the data to local Vector in foo:
>>>
>>> Vector& Another_Class::foo(Mesh& mesh, Function& func)
>>> 	{
>>> 		Vector vec = func.vector();
>>> 		Function func2(vec,mesh,func.element());
>>>
>>> 		AAA::BilineraForm a
>>> 		AAA::LinearForm L(func2)
>>>
>>> 		FEM:assemble(...)
>>> 		lu_solver.solve(...)
>>>
>>> 		return x;
>>> 	}
>>>
>>> I would dearly like to avoid this extra copy of a large vector. How
>>> should
>>> one do this?
>>>
>>> Regards,
>>> Dag Lindbo
>>
>> This should not happen so it looks like a bug. Passing a function as
>> argument to a form only has the effect that the pointer to the
>> function is placed in a list. During assembly, all functions in the
>> list will be interpolated to each element. The pointer is never
>> deleted.
>>
>> See if you can produce a simplest possible example that breaks and
>> maybe we can find out what goes wrong. Also check with valgrind if you
>> have it availabe and see if you can locate the offending line.
>>
>> /Anders
>> _______________________________________________
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>>
>
>
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