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From: Paul Smyth <paul.smyth@vi...>  20030616 14:43:35

Hi folks again, please excuse the verbosity. I'm proposing some changes to vnl_vector_fixed_ref and vnl_matrix_fixed_ref to make them more efficient and flexible. History  I had a number of functions which interpreted blocks of memory as fixedsize vectors or matrices, and passed them to other functions which operated on the fixedsize vector/matrix references. e.g. void AngleAxisToRotationMatrix(const vnl_vector_fixed_ref<double,3> & AngleAxis, vnl_matrix_fixed<double,3,3> & RotationMatrix); double MyObjectiveFunction(const vnl_vector<double> & Params) { vnl_matrix_fixed<double,3,3> R; // I know that params 3,4,5 are rotation vnl_vector_fixed_ref<double,3> ref(const_cast<double*>& Params[3]); // interpret elems 3,4,5 of Params as a rotation AngleAxisToRotationMatrix(ref, R); // fill out rotation matrix from angleaxis parameterisation } As (until about 1 year ago) vector_fixed was derived from vector_fixed_ref, the above function could be used with _either_ vnl_vector_fixed_ref or vnl_vector_fixed as 1st argument. This could also be rather slow for matrices, as a set of unnecessary row pointers were calculated whenever the ref was constructed. e.g. void SimpleUsage() { vnl_matrix_fixed<double,3,3> R; vnl_vector_fixed<double,3> rot; AngleAxisToRotationMatrix(rot, R); } Then vector_fixed was (very sensibly) broken away from the rest of the heirarchy, which meant my code no longer compiled. Problem  I would like a number of algorithms that use fixedsize vectors/matrices to work with either referencestomemory or with 'true' vector/matrix_fixed. Proposal  1) Make standalone fixed_ref classes which don't drag in the rest of the vector/matrix heirarchy, as at present, and only contain a pointer, and can therefore be copied efficiently. So these are smart pointers, with compiletime size info. 2) Wherever fixed_ref classes to be used, pass them by value (or if necessary const reference), so that conversions from true vector_fixed can be applied. 3) Make separate fixed_ref and fixed_ref_const classes which preserve constness properly in the type. Note that vec_fixed_ref can only be constructed from (vec_fixed &), and vec_fixed_ref_const can be constructed from (vec_fixed const &). template <typename T, unsigned n> class vnl_vector_fixed_ref_const { const T* data_; public: vnl_vector_fixed_ref_const(vnl_vector_fixed<T,n> const & rhs); explicit vnl_vector_fixed_ref_const(const T * dataptr); ... }; template <typename T, unsigned n> class vnl_vector_fixed_ref { T* data_; public: explicit vnl_vector_fixed_ref(T * dataptr); vnl_vector_fixed_ref( vnl_vector_fixed<T,n> & rhs); ... }; New Usage: void AngleAxisToRotationMatrix(vnl_vector_fixed_ref_const<double,3> AngleAxis, vnl_matrix_fixed<double,3,3> & RotationMatrix); double MyObjectiveFunction(const vnl_vector<double> & Params) { vnl_matrix_fixed<double,3,3> R; // I know that params 3,4,5 are rotation vnl_vector_fixed_ref_const<double,3> ref(&Params[3]); // interpret elems 3,4,5 of Params as a rotation  no const_cast AngleAxisToRotationMatrix(ref, R); // fill out rotation matrix from angleaxis parameterisation } SimpleUsage() compiles unchanged. Comments:   I'd like to get something that enables me to interchange between *fixed_ref and *fixed committed, as current vxl doesn't support a whole batch of my code, and I want to get in sync. The above scheme works reasonably, and has been implemented.  Noone else (that I know of) except me uses *fixed_ref, so there is no code that will be broken.  A grander scheme would be possible for *_fixed_ref encoding more information (element,row,column stride) into the type which might aid fixedsize algorithms (see Addendum). I have a number of fast fixedsize routines operating this way that might be suitable for inclusion in vxl if this more elaborate scheme were used. But I could imagine its about 3 bridges too far. Paul. Addendum  A fancier scheme might take the form of: template <typename T, unsigned n, int element_stride> class vnl_vector_fixed_ref; template <typename T, unsigned n, int row_stride, int col_stride> class vnl_matrix_fixed_ref; which would enable references to be taken to noncontiguous memory. e.g. template <typename T, unsigned rows, unsigned cols> vnl_vector_fixed_ref<T,cols,1> vnl_matrix_fixed<T,rows,cols>::row_reference(unsigned col_index); // take reference to contiguous block of memory for a row template <typename T, unsigned rows, unsigned cols> vnl_vector_fixed_ref<T,rows,cols> vnl_matrix_fixed<T,rows,cols>::col_reference(unsigned col_index); // take reference to 'spliced' memory for a column template <typename T, unsigned rows, unsigned cols> vnl_matrix_fixed_ref<T,cols,rows,cols,1> vnl_matrix_fixed<T,rows,cols>::transpose_reference(); // view fixed matrix as its transpose This would enable a function like: template <typename T, unsigned r, unsigned c, int r_s, int c_s, int el_s1, int el_s2> void mat_vec_mult(matrix_fixed_ref_const<T,r,c,r_s,c_s> A, vector_fixed_ref_const<T,c,el_s1> x, vector_fixed_ref<T,c,el_s2> y) // perform y = A x: could be used to perform mulitplication of matrix transposed as well etc. etc. This email, and any attachment, is confidential. If you have received it in error, please delete it from your system, do not use or disclose the information in any way, and notify me immediately. 
From: Gehua Yang <yangg2@cs...>  20030618 03:35:28

I like the idea of *fancier scheme*. To me, it is quite like the way how vil_image_view<T> is implemented. Intuitively, it will benefit computation of large matrices and large vectors (and small ones in terms of memory allocation), even though I haven't encountered this kind of situation on my research. It will be nice to have it in VXL. By the way, I did not get this one: "#undef vcl_abs #define vcl_abs vcl_abs". What's the trick behind this? As far as I remember about the header files for VC 7, we only define the functions, without any macros. Regards, Gehua Yang  Original Message  From: "Paul Smyth" <paul.smyth@...> To: "Vxlmaintainers (Email)" <vxlmaintainers@...> Sent: Monday, June 16, 2003 10:43 AM Subject: [Vxlmaintainers] vector + matrix fixed reference classes > Hi folks again, please excuse the verbosity. > > I'm proposing some changes to vnl_vector_fixed_ref and vnl_matrix_fixed_ref > to make them more efficient and flexible. > > History >  > I had a number of functions which interpreted blocks of memory as fixedsize > vectors or matrices, and passed them to other functions which operated on > the fixedsize vector/matrix references. > > e.g. > void AngleAxisToRotationMatrix(const vnl_vector_fixed_ref<double,3> & > AngleAxis, vnl_matrix_fixed<double,3,3> & RotationMatrix); > > double MyObjectiveFunction(const vnl_vector<double> & Params) { > vnl_matrix_fixed<double,3,3> R; > // I know that params 3,4,5 are rotation > vnl_vector_fixed_ref<double,3> ref(const_cast<double*>& Params[3]); // > interpret elems 3,4,5 of Params as a rotation > AngleAxisToRotationMatrix(ref, R); // fill out rotation matrix from > angleaxis parameterisation > } > > As (until about 1 year ago) vector_fixed was derived from vector_fixed_ref, > the above function could be used with _either_ > vnl_vector_fixed_ref or vnl_vector_fixed as 1st argument. This could also be > rather slow for matrices, as a set of unnecessary row pointers were > calculated whenever the ref was constructed. > > e.g. > void SimpleUsage() { > vnl_matrix_fixed<double,3,3> R; > vnl_vector_fixed<double,3> rot; > AngleAxisToRotationMatrix(rot, R); > } > > Then vector_fixed was (very sensibly) broken away from the rest of the > heirarchy, which meant my code no longer compiled. > > Problem >  > I would like a number of algorithms that use fixedsize vectors/matrices to > work with either referencestomemory or with > 'true' vector/matrix_fixed. > > Proposal >  > 1) Make standalone fixed_ref classes which don't drag in the rest of the > vector/matrix heirarchy, as at present, and only contain a pointer, and can > therefore be copied efficiently. So these are smart pointers, with > compiletime size info. > 2) Wherever fixed_ref classes to be used, pass them by value (or if > necessary const reference), so that conversions from true vector_fixed can > be applied. > 3) Make separate fixed_ref and fixed_ref_const classes which preserve > constness properly in the type. > > > Note that vec_fixed_ref can only be constructed from (vec_fixed &), and > vec_fixed_ref_const can be constructed from (vec_fixed const &). > > template <typename T, unsigned n> > class vnl_vector_fixed_ref_const > { > const T* data_; > public: > vnl_vector_fixed_ref_const(vnl_vector_fixed<T,n> const & rhs); > explicit vnl_vector_fixed_ref_const(const T * dataptr); > ... > }; > > template <typename T, unsigned n> > class vnl_vector_fixed_ref > { > T* data_; > public: > explicit vnl_vector_fixed_ref(T * dataptr); > vnl_vector_fixed_ref( vnl_vector_fixed<T,n> & rhs); > ... > }; > > New Usage: > void AngleAxisToRotationMatrix(vnl_vector_fixed_ref_const<double,3> > AngleAxis, vnl_matrix_fixed<double,3,3> & RotationMatrix); > > double MyObjectiveFunction(const vnl_vector<double> & Params) > { > vnl_matrix_fixed<double,3,3> R; > // I know that params 3,4,5 are rotation > vnl_vector_fixed_ref_const<double,3> ref(&Params[3]); // interpret elems > 3,4,5 of Params as a rotation  no const_cast > AngleAxisToRotationMatrix(ref, R); // fill out rotation matrix from > angleaxis parameterisation > } > > SimpleUsage() compiles unchanged. > > Comments: >  >  I'd like to get something that enables me to interchange between > *fixed_ref and *fixed committed, as current vxl doesn't support a whole > batch of my code, and I want to get in sync. The above scheme works > reasonably, and has been implemented. > >  Noone else (that I know of) except me uses *fixed_ref, so there is no code > that will be broken. > >  A grander scheme would be possible for *_fixed_ref encoding more > information (element,row,column stride) into the type > which might aid fixedsize algorithms (see Addendum). I have a number of > fast fixedsize routines operating this way that might be suitable for > inclusion in vxl if this more elaborate scheme were used. But I could > imagine its about 3 bridges too far. > > Paul. > > > > Addendum >  > > A fancier scheme might take the form of: > > template <typename T, unsigned n, int element_stride> > class vnl_vector_fixed_ref; > > template <typename T, unsigned n, int row_stride, int col_stride> > class vnl_matrix_fixed_ref; > > which would enable references to be taken to noncontiguous memory. > e.g. > > template <typename T, unsigned rows, unsigned cols> > vnl_vector_fixed_ref<T,cols,1> > vnl_matrix_fixed<T,rows,cols>::row_reference(unsigned col_index); > // take reference to contiguous block of memory for a row > > template <typename T, unsigned rows, unsigned cols> > vnl_vector_fixed_ref<T,rows,cols> > vnl_matrix_fixed<T,rows,cols>::col_reference(unsigned col_index); > // take reference to 'spliced' memory for a column > > template <typename T, unsigned rows, unsigned cols> > vnl_matrix_fixed_ref<T,cols,rows,cols,1> > vnl_matrix_fixed<T,rows,cols>::transpose_reference(); > // view fixed matrix as its transpose > > This would enable a function like: > > template <typename T, unsigned r, unsigned c, int r_s, int c_s, int el_s1, > int el_s2> > void mat_vec_mult(matrix_fixed_ref_const<T,r,c,r_s,c_s> A, > vector_fixed_ref_const<T,c,el_s1> x, vector_fixed_ref<T,c,el_s2> y) > // perform y = A x: could be used to perform mulitplication of matrix > transposed as well > etc. etc. > > > This email, and any attachment, is confidential. If you have received it in > error, please delete it from your system, do not use or disclose the > information in any way, and notify me immediately. > > >  > This SF.NET email is sponsored by: eBay > Great deals on office technology  on eBay now! Click here: > http://adfarm.mediaplex.com/ad/ck/7111169769165 > _______________________________________________ > Vxlmaintainers mailing list > Vxlmaintainers@... > https://lists.sourceforge.net/lists/listinfo/vxlmaintainers > 
From: Peter Vanroose <Peter.Vanroose@es...>  20030618 07:19:48

> ... Intuitively, it will benefit computation > of large matrices and large vectors ... As far as large vectors/matrices are concerned, there is already an interface for this: the classes vnl_matrix_ref and vnl_vector_ref. vnl_vector_fixed_ref is mainly useful for small size vectors, up to size 6 say, since it has to be instantiated for all sizes being used.  Peter. 
From: Gehua Yang <yangg2@cs...>  20030619 04:26:35

To make it a little clearer, I meant Paul's new design of vnl_matrix_fixed_ref & vnl_vector_fixed_ref (I copied his message in the following). I think this design would make it possible for the class to be transparent to operations such as transpose, retrieving a row or a column from a matrix. I looked at the code of current vnl_matrix_fixed_ref implementation. The features Paul suggested aren't there. Right now vnl_matrix_fixed_ref is inherited from vnl_matrix<T>. Compared with the way vnl_matrix_fixed is implemented, it is not very efficient. Please correct me if I am wrong. Gehua ================================================ > A fancier scheme might take the form of: > > template <typename T, unsigned n, int element_stride> > class vnl_vector_fixed_ref; > > template <typename T, unsigned n, int row_stride, int col_stride> > class vnl_matrix_fixed_ref; > > which would enable references to be taken to noncontiguous memory. > e.g. > > template <typename T, unsigned rows, unsigned cols> > vnl_vector_fixed_ref<T,cols,1> > vnl_matrix_fixed<T,rows,cols>::row_reference(unsigned col_index); > // take reference to contiguous block of memory for a row > > template <typename T, unsigned rows, unsigned cols> > vnl_vector_fixed_ref<T,rows,cols> > vnl_matrix_fixed<T,rows,cols>::col_reference(unsigned col_index); > // take reference to 'spliced' memory for a column > > template <typename T, unsigned rows, unsigned cols> > vnl_matrix_fixed_ref<T,cols,rows,cols,1> > vnl_matrix_fixed<T,rows,cols>::transpose_reference(); > // view fixed matrix as its transpose > > This would enable a function like: > > template <typename T, unsigned r, unsigned c, int r_s, int c_s, int el_s1, > int el_s2> > void mat_vec_mult(matrix_fixed_ref_const<T,r,c,r_s,c_s> A, > vector_fixed_ref_const<T,c,el_s1> x, vector_fixed_ref<T,c,el_s2> y) > // perform y = A x: could be used to perform mulitplication of matrix > transposed as well > etc. etc.  Original Message  From: "Peter Vanroose" <Peter.Vanroose@...> To: "Gehua Yang" <yangg2@...> Cc: "Paul Smyth" <paul.smyth@...>; "Vxlmaintainers (Email)" <vxlmaintainers@...> Sent: Wednesday, June 18, 2003 3:19 AM Subject: Re: [Vxlmaintainers] vector + matrix fixed reference classes > > ... Intuitively, it will benefit computation > > of large matrices and large vectors ... > > As far as large vectors/matrices are concerned, there is already an > interface for this: the classes vnl_matrix_ref and vnl_vector_ref. > > vnl_vector_fixed_ref is mainly useful for small size vectors, up to > size 6 say, since it has to be instantiated for all sizes being used. > > >  Peter. > > > 
From: Peter Vanroose <Peter.Vanroose@es...>  20030619 08:24:29

> I think this design would make it possible for the class to be > transparent to operations such as transpose, retrieving a row > or a column from a matrix. Sure; I support Paul's proposal. Just wanted to point out that when using **large** matrices and vectors, one should use the classes vnl_matrix_ref and vnl_vector_ref. vnl_matrix_fixed_ref and vnl_vector_fixed_ref are only meant for small matrices (up to 4x4 or so) and vectors (up to length 6 or so), as are the classes vnl_matrix_fixed and vnl_vector_fixed. On a side note: I propose to replace all uses of vnl_matrix and vnl_vector in contexts where the size is fixed (like in oxl/mvl: homographies, Fmatrices, ...) with vnl_matrix_fixed and vnl_vector_fixed.  Peter. 
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