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<DIV> Hi <A title=haroldo.santos@gmail.com href="">Haroldo</A> and
Ed,</DIV>
<DIV> </DIV>
<DIV>In order the disable storing branching, I think that
model.setNumberBeforeTrust(0); has to be in place too i.e. numberBeforeTrust_
has to be 0 as well.</DIV>
<DIV> </DIV>
<DIV>Take care.</DIV>
<DIV> </DIV>
<DIV>Gabrielle <BR></DIV>
<DIV> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=haroldo.santos@gmail.com
href="mailto:haroldo.santos@gmail.com">Haroldo Santos</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=ebul014@aucklanduni.ac.nz
href="mailto:ebul014@aucklanduni.ac.nz">Ed Bulog</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=cbc@list.coin-or.org
href="mailto:cbc@list.coin-or.org">cbc@list.coin-or.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, July 26, 2010 3:20 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Cbc] Using hotstarting
functionality with modifications</DIV>
<DIV><BR></DIV>Hi Ed,<BR><BR>I think that at the start of the MIP search there
are some very<BR>expensive routines which do not use any information of
previous<BR>solutions.<BR><BR>In particular, doing strong branching is very
expensive.<BR><BR>If you want to speed up the restart, perhaps one useful
option would<BR>be to disable strong branching.<BR><BR>setNumberStrong( 0
)<BR><BR><BR>On Mon, Jul 26, 2010 at 7:04 PM, Ed Bulog <<A
href="mailto:ebul014@aucklanduni.ac.nz">ebul014@aucklanduni.ac.nz</A>>
wrote:<BR>> Dear All,<BR>><BR>> I have a large IP which I will be
modifying constantly (by adding/removing<BR>> coulmns) and resolving after
each modification. I am trying to see if there<BR>> is some way I could
re-use the previous solution to make each solve faster.<BR>> The obvious
problem is that by adding and removing columns each time I have<BR>> no way
of guaranteeing that the previous solution will still be feasible,<BR>> let
alone optimal.<BR>><BR>> I have experimented with the cbc example files
(mostly hotstart.cpp,<BR>> modify.cpp and repeat.cpp). It would be ideal if
I could solve the problem,<BR>> modify it and then re-use the previous
solution in a hotstart. My basic<BR>> approach is:<BR>> - call
model.initialSolve()<BR>> - call model.branchandbound()<BR>> - save the
bestSolution array<BR>> - remove some columns from the reference
solver<BR>> - add some columns to the reference solver<BR>> - modify the
bestSolution array accordingly (i.e. remove entries<BR>> corresponding to
deleted columns and add zeros for new columns)<BR>> - call
model.resetToReferenceSolver()<BR>> - call
model.setHotstartSolution(<BR>> bestSolution)<BR>> - resolve using
model.branchandbound()<BR>><BR>> However, this approach does not seem to
do anything particularly useful.<BR>> branchandbound() does not appear to
do anything differently from what it<BR>> does when I do not use the
hotstart solution.<BR>><BR>> Does 'hotstarting' only work if the model
remains unchanged (as in<BR>> hotstart.cpp)? Does anyone have any other
suggestions? Your help is greatly<BR>> appreciated.<BR>><BR>> Thank
you for your time,<BR>><BR>> Ed<BR>><BR>>
_______________________________________________<BR>> Cbc mailing
list<BR>> <A
href="mailto:Cbc@list.coin-or.org">Cbc@list.coin-or.org</A><BR>> <A
href="http://list.coin-or.org/mailman/listinfo/cbc">http://list.coin-or.org/mailman/listinfo/cbc</A><BR>><BR>><BR><BR><BR><BR>--
<BR>=============================================================<BR>Haroldo
Gambini Santos<BR>Computing Department - Universidade Federal de Ouro Preto -
UFOP<BR>email: haroldo [at ] iceb.ufop.br<BR>home/research page: <A
href="http://www.iceb.ufop.br/decom/prof/haroldo/">http://www.iceb.ufop.br/decom/prof/haroldo/</A><BR><BR>"Computer
science is no more about computers than astronomy<BR>is about telescopes."
Edsger
Dijkstra<BR><BR><BR>_______________________________________________<BR>Cbc
mailing list<BR><A
href="mailto:Cbc@list.coin-or.org">Cbc@list.coin-or.org</A><BR><A
href="http://list.coin-or.org/mailman/listinfo/cbc">http://list.coin-or.org/mailman/listinfo/cbc</A><BR></BLOCKQUOTE>
<DIV><BR>
<BR>Gabrielle A. Grün, Ph.D. Student<BR>School of Computing Science<BR>Simon
Fraser University<BR>8888 University Drive<BR>Burnaby, BC<BR>V5A 1S6<BR><<A
href="http://www.cs.sfu.ca/~grun">http://www.cs.sfu.ca/~grun</A>> </DIV>
<DIV> </DIV>
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