#9061: Create an efficient SUM command
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Reporter: ncohen | Owner: jason, jkantor
Type: defect | Status: new
Priority: major | Milestone: sage-4.4.3
Component: numerical | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Changes (by ncohen):
* cc: mvngu (added)
Old description:
> Inequalities using <= and >= still do not work properly... :-/
>
> Nathann
New description:
This *HAS* to be changed :
{{{
p = MixedIntegerLinearProgram()
v = p.new_variable()
sage: %timeit sum([v[i] for i in xrange(900)])
5 loops, best of 3: 1.14 s per loop
}}}
With this new function :
{{{
def mipvariables_sum(L):
d = {}
for v in L:
for (id,coeff) in v._f.iteritems():
d[id] = coeff + d.get(id,0)
return LinearFunction(d)
}}}
It gives :
{{{
sage: from sage.numerical.mip import mipvariables_sum
sage: %timeit mipvariables_sum([v[i] for i in xrange(900)])
625 loops, best of 3: 1.5 ms per loop
}}}
Even though it requires a new function to add MIPVariables, it is still
better than nothing for the moment.
This patch will define the function given, and replace all the occurences
of "sum" in the graph files to have them use this optimization.
Nathann
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9061#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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