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[Noel Warren <>]

That worked a charm.  Simple_cartesian does output the right values without loss.  Below is a Point_3(0, 0, 1.1)

EPEC

3 { 9 11, 18 23, 6 7, -2 | 0 0 2.47698e+15 2.2518e+15 } 1

Simple_cartesian

3 { 9 11, 18 23, 6 7, -2 | 0 0 2476979795053773 2251799813685248 } 1

It does make my processing 50% slower though (50s to 74s).  This is fine to start off with but I shall want to improve this sooner or later.  It sounds like an easy fix.  I sifted through the code and was conviced the culprit was the gmpz << operator.  I guess I was wrong.

Am I right in understanding that the problem lies in Lazy_exact_nt.h somewhere?  I might give it a shot if there is any chance you'll use the changes.

2012/11/19 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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