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[Noel Warren <>]

I am working with minkowski sums so EPEC kernel is my only option (I believe).  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) <>

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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