#4000: Implement QQ['x'] via Flint ZZ['x'] + denominator
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Reporter: malb | Owner: somebody
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.3.2
Component: basic arithmetic | Keywords:
Author: Sebastian Pancratz, Martin Albrecht | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by spancratz):
I am sorry for only getting on with this today. Just now I tried to re-
produce the problem in plain C with FLINT, but needless to say, I didn't
manage. A simple-minded reproduction of the relevant code executed in no
time and without any problems. Currently, I am completely out of ideas on
how to fix this problem. That's why I'll raise the issue on sage-devel
and conclude this message with a description of the behaviour that I
experience on my machine (Lenovo T500 laptop, Intel Core2 Duo CPU, Ubuntu
9.10):
After applying all patches from this ticket to a 4.3.1.rc0 installation,
modify the ``else`` block from line 882 in
``sage/libs/flint/fmpq_poly_linkage.pxi`` to the following:
{{{
print "In case 3B"
t = fmpz_init(limbs)
print "den_fit_limbs"
__fmpq_poly_den_fit_limbs(r, limbs + fmpz_size(a.den))
print "pow_ui"
fmpz_pow_ui(t, lead, m)
print "mul"
fmpz_mul(r.den, t, a.den)
print "clear"
fmpz_clear(t)
}}}
This only includes the ``print`` commands.
Then, upon executing the same sequence of commands that produce the crash
in Alex' previous message, I receive the following output:
{{{
sage: R.<x> = QQ[]
sage: f = 3/2*x - 1/3
sage: %time _ = f % f
In case 3B
den_fit_limbs
pow_ui
mul
clear
CPU times: user 19.10 s, sys: 0.54 s, total: 19.64 s
Wall time: 19.72 s
}}}
What I find very strange (besides the fact that this takes 20s to obtain
the correct result) is that there are two very noticeable delays of a
couple of seconds, one after the output ``"pow_ui"``, and another after
the output of ``"mul"``.
Sebastian
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4000#comment:47>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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