CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 11/19/2012 11:04 AM, Noel Warren wrote:
> I am working with minkowski sums so EPEC kernel is my only option (I
> believe).
It should work fine (even if slower).

Sebastien.

>  If you want me to run a "hello tetrahedron" example just to
> compare the two kernels let me know.  I have seen no evidence of EPEC
> using doubles as a default in its out stream.  It just seems that when
> the integers are too big it decides to convert them to double instead of
> printing all the characters representing the integer.
>
> I had to google IIRC.  I thought it was a kernel or number format of
> some sort :D
>
>
> 2012/11/19 Sebastien Loriot (GeometryFactory) 
> <
> <mailto:>>
>
>     Hi Noel,
>
>     Could you try with CGAL::Simple_cartesian<CGAL::__Gmpq> ?
>
>     The stream operator with EPEC kernel is using to_double on the
>     coordinates IIRC.
>
>     Sebastien.
>
>
>     On 11/19/2012 09:50 AM, Noel Warren wrote:
>
>         I'm using the Exact_predicates_exact___constructions kernel to
>         construct
>         my Nef polyhedra and I believe I've run into a bug.  The Nef
>         seems to
>         have no problem being stringified.  When I try to rebuild the
>         nef with
>         the string it will often fail.
>
>         I try a simple tetrahedron with points
>         (0,0,0)(1,0,0)(0,1,0)(0,0,1) and
>         everything works fine.  But if I change the last point to have a
>         value
>         of (0,0,1.1) it fails.  You might think that the problem has
>         something
>         to do with floats, but it doesn't.  1.5 works fine as does 0.75
>
>         As you probably know, the points are represented as a quotient
>         with both
>         the numerator and denominator being integers.  The problem seems
>         to be
>         that when these integers (gmpz) are being output with the <<
>         operator
>         they get abbreviated when too long (eg: 2.47698e+15).  This not only
>         leads to a loss in precision but means the file can not be read,
>         as gmpz
>         cannot parse the integer in that format.  Here is my failing
>         tetrahedron
>         example (see fourth point) ...
>
>         Selective Nef Complex
>         standard
>         vertices   4
>         halfedges  12
>         facets     8
>         volumes    2
>         shalfedges 24
>         shalfloops 0
>         sfaces     8
>         0 { 0 2, 0 5, 0 1, -2 | 0 0 0 1 } 1
>         1 { 3 5, 6 11, 2 3, -2 | 1 0 0 1 } 1
>         2 { 6 8, 12 17, 4 5, -2 | 0 1 0 1 } 1
>         3 { 9 11, 18 23, 6 7, -2 | 0 0 2.47698e+15 2.2518e+15 } 1
>         0 { 4, 0, 0 0 | 1 0 0 1 } 1
>         1 { 6, 0, 0 1 | 0 1 0 1 } 1
>         2 { 9, 0, 0 3 | 0 0 1 1 } 1
>         3 { 7, 1, 0 6 | -1 1 0 1 } 1
>         4 { 0, 1, 0 7 | -1 0 0 1 } 1
>         5 { 11, 1, 0 9 | -2.2518e+15 0 2.47698e+15 1 } 1
>         6 { 1, 2, 0 12 | 0 -1 0 1 } 1
>         7 { 3, 2, 0 13 | 1 -1 0 1 } 1
>         8 { 10, 2, 0 15 | 0 -2.2518e+15 2.47698e+15 1 } 1
>         9 { 2, 3, 0 18 | 0 0 -1 1 } 1
>         10 { 8, 3, 0 19 | 0 2.2518e+15 -2.47698e+15 1 } 1
>         11 { 5, 3, 0 21 | 2.2518e+15 0 -2.47698e+15 1 } 1
>         0 { 1, 4 , , 0 | 0 -1 0 0 } 1
>         1 { 0, 5 , , 1 | 0 1 0 0 } 1
>         2 { 3, 20 , , 0 | 2.47698e+15 2.47698e+15 2.2518e+15
>         -2.47698e+15 } 1
>         3 { 2, 21 , , 1 | -2.47698e+15 -2.47698e+15 -2.2518e+15
>         2.47698e+15 } 1
>         4 { 5, 2 , , 0 | -1 0 0 0 } 1
>         5 { 4, 3 , , 1 | 1 0 0 0 } 1
>         6 { 7, 0 , , 0 | 0 0 -1 0 } 1
>         7 { 6, 1 , , 1 | 0 0 1 0 } 1
>         0 { 0 } 0
>         1 { 1 } 1
>         0 { 1, 4, 2, 0, 1, 6, 12, 6 | 0 0 1 0 } 1
>         1 { 0, 3, 5, 1, 0, 13, 7, 7 | 0 0 -1 0 } 1
>         2 { 3, 0, 4, 1, 1, 16, 18, 4 | 1 0 0 0 } 1
>         3 { 2, 5, 1, 2, 0, 19, 17, 5 | -1 0 0 0 } 1
>         4 { 5, 2, 0, 2, 1, 22, 8, 0 | 0 1 0 0 } 1
>         5 { 4, 1, 3, 0, 0, 9, 23, 1 | 0 -1 0 0 } 1
>         6 { 7, 10, 8, 3, 3, 12, 0, 6 | 0 0 1 0 } 1
>         7 { 6, 9, 11, 4, 2, 1, 13, 7 | 0 0 -1 0 } 1
>         8 { 9, 6, 10, 4, 3, 4, 22, 0 | 0 1 0 0 } 1
>         9 { 8, 11, 7, 5, 2, 23, 5, 1 | 0 -1 0 0 } 1
>         10 { 11, 8, 6, 5, 3, 20, 14, 2 | -2.47698e+15 -2.47698e+15
>         -2.2518e+15 0 } 1
>         11 { 10, 7, 9, 3, 2, 15, 21, 3 | 2.47698e+15 2.47698e+15
>         2.2518e+15 0 } 1
>         12 { 13, 16, 14, 6, 5, 0, 6, 6 | 0 0 1 0 } 1
>         13 { 12, 15, 17, 7, 4, 7, 1, 7 | 0 0 -1 0 } 1
>         14 { 15, 12, 16, 7, 5, 10, 20, 2 | -2.47698e+15 -2.47698e+15
>         -2.2518e+15
>         0 } 1
>         15 { 14, 17, 13, 8, 4, 21, 11, 3 | 2.47698e+15 2.47698e+15
>         2.2518e+15 0 } 1
>         16 { 17, 14, 12, 8, 5, 18, 2, 4 | 1 0 0 0 } 1
>         17 { 16, 13, 15, 6, 4, 3, 19, 5 | -1 0 0 0 } 1
>         18 { 19, 22, 20, 9, 7, 2, 16, 4 | 1 0 0 0 } 1
>         19 { 18, 21, 23, 10, 6, 17, 3, 5 | -1 0 0 0 } 1
>         20 { 21, 18, 22, 10, 7, 14, 10, 2 | -2.47698e+15 -2.47698e+15
>         -2.2518e+15 0 } 1
>         21 { 20, 23, 19, 11, 6, 11, 15, 3 | 2.47698e+15 2.47698e+15
>         2.2518e+15 0 } 1
>         22 { 23, 20, 18, 11, 7, 8, 4, 0 | 0 1 0 0 } 1
>         23 { 22, 19, 21, 9, 6, 5, 9, 1 | 0 -1 0 0 } 1
>         0 { 0, 1 , , , 0 } 0
>         1 { 0, 0 , , , 1 } 1
>         2 { 1, 7 , , , 0 } 0
>         3 { 1, 6 , , , 1 } 1
>         4 { 2, 13 , , , 0 } 0
>         5 { 2, 12 , , , 1 } 1
>         6 { 3, 19 , , , 0 } 0
>         7 { 3, 18 , , , 1 } 1
>         /* end Selective Nef complex */
>
>
>
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