Eigen ref with child matrix class - c++

Question

I've got the following code:
#include <iostream>
#include <eigen3/Eigen/Dense>
class MyVectorType: public Eigen::Matrix<double, 3, 1> {
public:
MyVectorType(void) :
Eigen::Matrix<double, 3, 1>() {
}
typedef Eigen::Matrix<double, 3, 1> Base;
// This constructor allows you to construct MyVectorType from Eigen expressions
template<typename OtherDerived>
MyVectorType(const Eigen::MatrixBase<OtherDerived>& other) :
Eigen::Matrix<double, 3, 1>(other) {
}
// This method allows you to assign Eigen expressions to MyVectorType
template<typename OtherDerived>
MyVectorType & operator=(const Eigen::MatrixBase<OtherDerived>& other) {
this->Base::operator=(other);
return *this;
}
//other custom methods here
};
void init(Eigen::Ref<MyVectorType>& m) {
for (int i = 0; i < 3; i++)
for (int j = 0; j < 1; j++)
m(i, j) = 1;
}
int main() {
Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic, Eigen::AutoAlign, 12,
12> mm(3, 1);
Eigen::Ref<MyVectorType> rr(mm);
init(rr);
std::cout << mm << std::endl;
return 0;
}
I defined my own class but when I try to the Ref class I have the following error from gcc:
make all
Building file: ../main.cpp
Invoking: GCC C++ Compiler
g++ -std=c++98 -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"main.d" -MT"main.o" -o "main.o" "../main.cpp"
In file included from /usr/include/eigen3/Eigen/Core:449:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Map.h: In instantiation of ‘struct Eigen::internal::traits<Eigen::Map<MyVectorType, 0, Eigen::OuterStride<> > >’:
/usr/include/eigen3/Eigen/src/Core/Ref.h:18:8: required from ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/util/ForwardDeclarations.h:32:54: required from ‘struct Eigen::internal::accessors_level<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/util/ForwardDeclarations.h:113:75: required from ‘class Eigen::RefBase<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/Ref.h:190:76: required from ‘class Eigen::Ref<MyVectorType>’
../main.cpp:26:10: required from here
/usr/include/eigen3/Eigen/src/Core/Map.h:18:8: error: invalid use of incomplete type ‘struct Eigen::internal::traits<MyVectorType>’
struct traits<Map<PlainObjectType, MapOptions, StrideType> >
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/eigen3/Eigen/Core:346:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/util/ForwardDeclarations.h:17:29: note: declaration of ‘struct Eigen::internal::traits<MyVectorType>’
template<typename T> struct traits;
^~~~~~
In file included from /usr/include/eigen3/Eigen/Core:449:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Map.h:30:32: error: incomplete type ‘Eigen::internal::traits<Eigen::Map<MyVectorType, 0, Eigen::OuterStride<> > >::TraitsBase {aka Eigen::internal::traits<MyVectorType>}’ used in nested name specifier
Flags0 = TraitsBase::Flags & (~NestByRefBit),
~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
In file included from /usr/include/eigen3/Eigen/Core:348:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/util/XprHelper.h: In instantiation of ‘struct Eigen::internal::is_lvalue<MyVectorType>’:
/usr/include/eigen3/Eigen/src/Core/Map.h:31:47: required from ‘struct Eigen::internal::traits<Eigen::Map<MyVectorType, 0, Eigen::OuterStride<> > >’
/usr/include/eigen3/Eigen/src/Core/Ref.h:18:8: required from ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/util/ForwardDeclarations.h:32:54: required from ‘struct Eigen::internal::accessors_level<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/util/ForwardDeclarations.h:113:75: required from ‘class Eigen::RefBase<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/Ref.h:190:76: required from ‘class Eigen::Ref<MyVectorType>’
../main.cpp:26:10: required from here
/usr/include/eigen3/Eigen/src/Core/util/XprHelper.h:642:53: error: incomplete type ‘Eigen::internal::traits<MyVectorType>’ used in nested name specifier
bool(traits<ExpressionType>::Flags & LvalueBit) };
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
In file included from /usr/include/eigen3/Eigen/Core:448:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/MapBase.h: In instantiation of ‘class Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>’:
/usr/include/eigen3/Eigen/src/Core/Ref.h:58:34: required from ‘class Eigen::RefBase<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/Ref.h:190:76: required from ‘class Eigen::Ref<MyVectorType>’
../main.cpp:26:10: required from here
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: error: no type named ‘XprKind’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
template<typename Derived> class MapBase<Derived, ReadOnlyAccessors>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:42:62: error: no type named ‘XprKind’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
typedef typename internal::dense_xpr_base<Derived>::type Base;
^~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:43:10: error: ‘RowsAtCompileTime’ is not a member of ‘Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
enum {
^
/usr/include/eigen3/Eigen/src/Core/MapBase.h:43:10: error: ‘ColsAtCompileTime’ is not a member of ‘Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/MapBase.h:49:61: error: no type named ‘StorageKind’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
typedef typename internal::traits<Derived>::StorageKind StorageKind;
^~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:50:56: error: no type named ‘Scalar’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
typedef typename internal::traits<Derived>::Scalar Scalar;
^~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:51:60: error: no type named ‘Scalar’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
typedef typename internal::packet_traits<Scalar>::type PacketScalar;
^~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:52:46: error: no type named ‘Scalar’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
typedef typename NumTraits<Scalar>::Real RealScalar;
^~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:57:22: error: no type named ‘Scalar’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
PointerType;
^~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:59:17: error: using-declaration for non-member at class scope
using Base::derived;
^~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:63:17: error: using-declaration for non-member at class scope
using Base::MaxRowsAtCompileTime;
^~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:64:17: error: using-declaration for non-member at class scope
using Base::MaxColsAtCompileTime;
^~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:65:17: error: using-declaration for non-member at class scope
using Base::MaxSizeAtCompileTime;
^~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:66:17: error: using-declaration for non-member at class scope
using Base::IsVectorAtCompileTime;
^~~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:67:17: error: using-declaration for non-member at class scope
using Base::Flags;
^~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:68:17: error: using-declaration for non-member at class scope
using Base::IsRowMajor;
^~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:70:17: error: using-declaration for non-member at class scope
using Base::rows;
^~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:71:17: error: using-declaration for non-member at class scope
using Base::cols;
^~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:72:17: error: using-declaration for non-member at class scope
using Base::size;
^~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:73:17: error: using-declaration for non-member at class scope
using Base::coeff;
^~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:74:17: error: using-declaration for non-member at class scope
using Base::coeffRef;
^~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:75:17: error: using-declaration for non-member at class scope
using Base::lazyAssign;
^~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:76:17: error: using-declaration for non-member at class scope
using Base::eval;
^~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:78:17: error: using-declaration for non-member at class scope
using Base::innerStride;
^~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:79:17: error: using-declaration for non-member at class scope
using Base::outerStride;
^~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:80:17: error: using-declaration for non-member at class scope
using Base::rowStride;
^~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:81:17: error: using-declaration for non-member at class scope
using Base::colStride;
^~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:84:25: error: using-declaration for non-member at class scope
using Base::operator=;
^
In file included from /usr/include/eigen3/Eigen/Core:72:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h: In instantiation of ‘class Eigen::RefBase<Eigen::Ref<MyVectorType> >’:
/usr/include/eigen3/Eigen/src/Core/Ref.h:190:76: required from ‘class Eigen::Ref<MyVectorType>’
../main.cpp:26:10: required from here
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: no type named ‘Scalar’ in ‘struct Eigen::internal::traits<Eigen::RefBase<Eigen::Ref<MyVectorType> > >’
EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: no type named ‘Scalar’ in ‘struct Eigen::internal::traits<Eigen::RefBase<Eigen::Ref<MyVectorType> > >’
EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
^
In file included from /usr/include/eigen3/Eigen/Core:72:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: no type named ‘StorageKind’ in ‘struct Eigen::internal::traits<Eigen::RefBase<Eigen::Ref<MyVectorType> > >’
EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: no type named ‘StorageIndex’ in ‘struct Eigen::internal::traits<Eigen::RefBase<Eigen::Ref<MyVectorType> > >’
EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: ‘RowsAtCompileTime’ is not a member of ‘Eigen::internal::traits<Eigen::RefBase<Eigen::Ref<MyVectorType> > >’
EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: ‘ColsAtCompileTime’ is not a member of ‘Eigen::internal::traits<Eigen::RefBase<Eigen::Ref<MyVectorType> > >’
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: ‘MaxSizeAtCompileTime’ is not a member of ‘Eigen::RefBase<Eigen::Ref<MyVectorType> >::Base {aka Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>}’
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: ‘IsVectorAtCompileTime’ is not a member of ‘Eigen::RefBase<Eigen::Ref<MyVectorType> >::Base {aka Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>}’
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: no members matching ‘Eigen::RefBase<Eigen::Ref<MyVectorType> >::Base {aka Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>}::derived’ in ‘Eigen::RefBase<Eigen::Ref<MyVectorType> >::Base {aka class Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>}’
EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:67:3: error: no members matching ‘Eigen::RefBase<Eigen::Ref<MyVectorType> >::Base {aka Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>}::const_cast_derived’ in ‘Eigen::RefBase<Eigen::Ref<MyVectorType> >::Base {aka class Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>}’
EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
^
In file included from /usr/include/eigen3/Eigen/Core:72:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h: In instantiation of ‘class Eigen::Ref<MyVectorType>’:
../main.cpp:26:10: required from here
/usr/include/eigen3/Eigen/src/Core/Ref.h:201:5: error: no type named ‘Scalar’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:201:5: error: no type named ‘Scalar’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
^
In file included from /usr/include/eigen3/Eigen/Core:72:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h:201:5: error: no type named ‘StorageKind’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:201:5: error: no type named ‘StorageIndex’ in ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:201:5: error: ‘RowsAtCompileTime’ is not a member of ‘Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:201:5: error: ‘ColsAtCompileTime’ is not a member of ‘Eigen::internal::traits<Eigen::Ref<MyVectorType> >’
/usr/include/eigen3/Eigen/src/Core/Ref.h:201:5: error: no members matching ‘Eigen::Ref<MyVectorType>::Base {aka Eigen::RefBase<Eigen::Ref<MyVectorType> >}::derived’ in ‘Eigen::Ref<MyVectorType>::Base {aka class Eigen::RefBase<Eigen::Ref<MyVectorType> >}’
EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
^
/usr/include/eigen3/Eigen/src/Core/Ref.h:201:5: error: no members matching ‘Eigen::Ref<MyVectorType>::Base {aka Eigen::RefBase<Eigen::Ref<MyVectorType> >}::const_cast_derived’ in ‘Eigen::Ref<MyVectorType>::Base {aka class Eigen::RefBase<Eigen::Ref<MyVectorType> >}’
EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
^
../main.cpp: In function ‘void init(Eigen::Ref<MyVectorType>&)’:
../main.cpp:26:10: error: no match for call to ‘(Eigen::Ref<MyVectorType>) (int&, int&)’
m(i, j) = 1;
^
In file included from /usr/include/eigen3/Eigen/Core:450:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h: In instantiation of ‘struct Eigen::internal::traits<Eigen::Ref<MyVectorType> >::match<Eigen::Matrix<double, -1, -1, 0, 12, 12> >’:
/usr/include/eigen3/Eigen/src/Core/Ref.h:197:63: required by substitution of ‘template<class Derived> Eigen::Ref<MyVectorType>::Ref(const Eigen::PlainObjectBase<Derived>&, typename Eigen::internal::enable_if<(bool)(Eigen::internal::traits<Eigen::Ref<MyVectorType> >::match<Derived>::MatchAtCompileTime), Derived>::type*) [with Derived = Eigen::Matrix<double, -1, -1, 0, 12, 12>]’
../main.cpp:32:32: required from here
/usr/include/eigen3/Eigen/src/Core/Ref.h:44:25: error: incomplete type ‘Eigen::internal::traits<MyVectorType>’ used in nested name specifier
AlignmentMatch = (int(traits<PlainObjectType>::Alignment)==int(Unaligned)) || (DerivedAlignment >= int(Alignment)), // FIXME the first condition is not very clear, it should be replaced by the required alignment
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/eigen3/Eigen/Core:347:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h: In instantiation of ‘static void Eigen::PlainObjectBase<Derived>::_check_template_params() [with Derived = Eigen::Matrix<double, 3, 1, 0, 12, 12>]’:
/usr/include/eigen3/Eigen/src/Core/Matrix.h:261:35: required from ‘Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols>::Matrix() [with _Scalar = double; int _Rows = 3; int _Cols = 1; int _Options = 0; int _MaxRows = 12; int _MaxCols = 12]’
../main.cpp:7:58: required from here
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h:899:7: error: ‘INVALID_MATRIX_TEMPLATE_PARAMETERS’ is not a member of ‘Eigen::internal::static_assertion<false>’
EIGEN_STATIC_ASSERT((EIGEN_IMPLIES(MaxRowsAtCompileTime==1 && MaxColsAtCompileTime!=1, (Options&RowMajor)==RowMajor)
^
In file included from /usr/include/eigen3/Eigen/Core:450:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h: In instantiation of ‘Eigen::RefBase<Derived>::RefBase() [with Derived = Eigen::Ref<MyVectorType>]’:
/usr/include/eigen3/Eigen/src/Core/Ref.h:208:5: required from ‘Eigen::Ref<PlainObjectType, Options, StrideType>::Ref(Eigen::PlainObjectBase<OtherDerived>&, typename Eigen::internal::enable_if<(bool)(typename Eigen::internal::traits<Eigen::Ref<PlainObjectType, RefOptions, StrideType> >::match<Derived>::MatchAtCompileTime), Derived>::type*) [with Derived = Eigen::Matrix<double, -1, -1, 0, 12, 12>; PlainObjectType = MyVectorType; int Options = 0; StrideType = Eigen::OuterStride<>; typename Eigen::internal::enable_if<(bool)(typename Eigen::internal::traits<Eigen::Ref<PlainObjectType, RefOptions, StrideType> >::match<Derived>::MatchAtCompileTime), Derived>::type = Eigen::Matrix<double, -1, -1, 0, 12, 12>]’
../main.cpp:32:32: required from here
/usr/include/eigen3/Eigen/src/Core/Ref.h:86:100: error: no matching function for call to ‘Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase(int, int, int)’
StrideType::InnerStrideAtCompileTime==Dynamic?0:StrideType::InnerStrideAtCompileTime)
^
In file included from /usr/include/eigen3/Eigen/Core:448:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate: Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase()
template<typename Derived> class MapBase<Derived, ReadOnlyAccessors>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate expects 0 arguments, 3 provided
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate: Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase(const Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>&)
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate expects 1 argument, 3 provided
In file included from /usr/include/eigen3/Eigen/Core:450:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h: In instantiation of ‘void Eigen::RefBase<Derived>::construct(Expression&) [with Expression = Eigen::Matrix<double, -1, -1, 0, 12, 12>; Derived = Eigen::Ref<MyVectorType>]’:
/usr/include/eigen3/Eigen/src/Core/Ref.h:210:22: required from ‘Eigen::Ref<PlainObjectType, Options, StrideType>::Ref(Eigen::PlainObjectBase<OtherDerived>&, typename Eigen::internal::enable_if<(bool)(typename Eigen::internal::traits<Eigen::Ref<PlainObjectType, RefOptions, StrideType> >::match<Derived>::MatchAtCompileTime), Derived>::type*) [with Derived = Eigen::Matrix<double, -1, -1, 0, 12, 12>; PlainObjectType = MyVectorType; int Options = 0; StrideType = Eigen::OuterStride<>; typename Eigen::internal::enable_if<(bool)(typename Eigen::internal::traits<Eigen::Ref<PlainObjectType, RefOptions, StrideType> >::match<Derived>::MatchAtCompileTime), Derived>::type = Eigen::Matrix<double, -1, -1, 0, 12, 12>]’
../main.cpp:32:32: required from here
/usr/include/eigen3/Eigen/src/Core/Ref.h:101:7: error: no matching function for call to ‘Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase(Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, 12, 12> >::Scalar*, int, Eigen::EigenBase<Eigen::Matrix<double, -1, -1, 0, 12, 12> >::Index)’
::new (static_cast<Base*>(this)) Base(expr.data(), 1, expr.size());
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/eigen3/Eigen/Core:448:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate: Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase()
template<typename Derived> class MapBase<Derived, ReadOnlyAccessors>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate expects 0 arguments, 3 provided
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate: Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase(const Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>&)
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate expects 1 argument, 3 provided
In file included from /usr/include/eigen3/Eigen/Core:450:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h:106:7: error: no matching function for call to ‘Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase(Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, 12, 12> >::Scalar*, Eigen::EigenBase<Eigen::Matrix<double, -1, -1, 0, 12, 12> >::Index, int)’
::new (static_cast<Base*>(this)) Base(expr.data(), expr.size(), 1);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/eigen3/Eigen/Core:448:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate: Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase()
template<typename Derived> class MapBase<Derived, ReadOnlyAccessors>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate expects 0 arguments, 3 provided
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate: Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase(const Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>&)
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate expects 1 argument, 3 provided
In file included from /usr/include/eigen3/Eigen/Core:450:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/Ref.h:109:7: error: no matching function for call to ‘Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase(Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, 12, 12> >::Scalar*, Eigen::Index, Eigen::Index)’
::new (static_cast<Base*>(this)) Base(expr.data(), expr.rows(), expr.cols());
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/eigen3/Eigen/Core:448:0,
from /usr/include/eigen3/Eigen/Dense:1,
from ../main.cpp:2:
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate: Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase()
template<typename Derived> class MapBase<Derived, ReadOnlyAccessors>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate expects 0 arguments, 3 provided
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate: Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>::MapBase(const Eigen::MapBase<Eigen::Ref<MyVectorType>, 0>&)
/usr/include/eigen3/Eigen/src/Core/MapBase.h:37:34: note: candidate expects 1 argument, 3 provided
Is possible to pass by reference a dynamic matrix to a fixed one using a custom child class?

Answer 1

Eigen::Ref is not intended to work with own custom types (that would be possible, but is way to complicated for this purpose). Simply use Eigen::Ref<MyVectorType::Base>. Also if a Ref is intended to be an L-value (i.e., writable), you should pass it by-value, like so
void init(Eigen::Ref<MyVectorType::Base> m) {
// ...
That way you don't need to manually generate a temporary when calling init:
int main() {
Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic, Eigen::AutoAlign, 12,
12> mm(3, 1);
// Eigen::Ref<MyVectorType> rr(mm); // not necessary!
init(mm); // implicitly generates a temporary `Ref` object
// ...
For more details, see the online documentation of Ref: https://eigen.tuxfamily.org/dox/classEigen_1_1Ref.html