isl_tab_sample: perform greedy search before performing basis reduction
authorSven Verdoolaege <skimo@kotnet.org>
Mon, 19 Nov 2012 11:25:11 +0000 (12:25 +0100)
committerSven Verdoolaege <skimo@kotnet.org>
Tue, 20 Nov 2012 11:12:44 +0000 (12:12 +0100)
commit9746df494d6da272ba78205c853896ab8987e173
tree259d44a8f5f213f39d1d429b00db0dac0b9e5c90
parent2ff4d0ffb9d19b47c4b82842096c12503c50e89d
isl_tab_sample: perform greedy search before performing basis reduction

While basis reduction is very useful on difficult problems, it is
overkill on easy problems.  In fact, the basis reduction computation
can be quite expensive, especially in the presence of large coefficients.
This may happen in particular during the affine hull computation
when only a few sample points have been found so far.  If these
points have large values, then the equalities that describe their
affine hull may have coefficients with larger values still.

Perform a greedy search before computing a reduced basis.
We also perform a greedy search after computing the reduced basis
just in case the problem has become easy through this basis reduction.

Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>
isl_sample.c