padic _ntl_rep_abs incorrect for extension fields

[saraedum]

Currently, _ntl_rep_abs() is incorrect for some extension fields::

sage: K=Zp(3,3)
sage: R.<a>=K[]
sage: L.<a>=K.extension(a^2-3)
sage: L(3)._ntl_rep_abs()
([57], 0)

The correct result here would be ([3],0).

The attached patch fixes this.

CC: @roed314

Component: padics

Keywords: sd59, days71

Author: Julian Rueth

Branch/Commit: u/saraedum/ticket/13651 @ c3875b9

Issue created by migration from https://trac.sagemath.org/ticket/13651

[saraedum]

comment:1

Attachment: trac_13651.patch.gz

There was a problem in _internal_lshift(). I rewrote it to use multiplications of the form x^e/p which can be done without a precision loss.

It initially took me a while to understand what _ntl_rep_abs() does. I reformatted it heavily in this patch but I (hopefully) did not change what it does at all. I hope it's easier to understand now.

[saraedum]

comment:2

The doctests in the padics directory pass. Let's see what the patchbot thinks about everything else.

---

This also fixes a todo in the code:

sage: ZZ(W(5)) # todo: this should be different... 
381469726562505 

It seems that roed wrote that todo a few years ago. (added him as CC)

[saraedum]

Branch: u/saraedum/ticket/13651

[saraedum]

Changed keywords from none to sd59

[vbraun]

Commit: b87ff51

[vbraun]

comment:9

looks good but branch doesn't apply currently

---

New commits:

b87ff51

Trac #13651: fixed a precision problem in _internal_lshift(), _ntl_rep_abs() of padics

[saraedum]

comment:10

(changed the status so it shows up in my list of tickets needing work)

[7ed8c4ca-6d56-4ae9-953a-41e42b4ed313]

Branch pushed to git repo; I updated commit sha1. New commits:

c3875b9

Merge branch 'develop' into t/13651/ticket/13651

[7ed8c4ca-6d56-4ae9-953a-41e42b4ed313]

Changed commit from b87ff51 to c3875b9

[saraedum]

Changed keywords from sd59 to sd59, days71