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Hi Christina,<br>
<br>
ok, this explains the behavior. The original objective scale should
be 1, but this itself should not be a problem. However, I don't see
how this can be changed to 0 (which SCIP version do you use?), so
perhaps you want to use valgrind to check that you don't have any
memory corruptions.<br>
<br>
Best,<br>
Gerald<br>
<br>
<div class="moz-cite-prefix">Am 10.03.2015 um 19:19 schrieb Cristina
Núñez del Toro:<br>
</div>
<blockquote
cite="mid:CAKuRvOEhi+feZLn2u2B71x_CEsnZ1OO1dxmaxkgzA7_w_zYrxA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>
<div>Hello again,<br>
<br>
</div>
I have already solve the problem! Because following binpacking
example, I just left SCIPsetObjIntegral() without noticed that
my solution does not fullfill this condition. Now, I obtain
the optimal value of 3.2 recognized. However,
SCIPgetOrigObjscale() and SCIPgetTransObjscale() are still 0
and 1, respectivelly. Should I expect both values equal to 1 ?<br>
<br>
</div>
Thanks for all,<br>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2015-03-10 17:52 GMT+01:00 Gerald
Gamrath <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:gamrath@zib.de" target="_blank">gamrath@zib.de</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>Hi Christina,<br>
<br>
</div>
<span class="">
<blockquote type="cite">
<div dir="ltr">
<div>
<div>I have revised the initial parameters
settings and, as you said, I had the heuristic
as disabled (and also the separating and
presolving). Now, the heuristic is not disabled
but the separating and presolving. I'm sending
you the statistics file. I'm not using the
runshell SCIP command line interface, so I don't
know where can obtain the log file. Is there
another way to obtain it without including the
SCIP command line?<br>
</div>
</div>
</div>
</blockquote>
</span> But you get output lines from SCIP don't you? Just
pipe them to some file and send this to me.<span class=""><br>
<br>
<blockquote type="cite">
<div dir="ltr">
<div>
<div>What I have discovered is that the initial
cutoff bound (3.0001) is lower than my (already
known) optimal value (3.2). So, even the LP gets
an integer solution with value of 3.2, scip
never takes this bound into account. I have
already checked my code and I never set this
cutoff bound, so I suspect this 3.0001 is set by
scip from the very beginning. In fact, I have
tried starting the B&Price with different
initial columns. Even if the initial columns
yields feasible or infeasible solution, the
cutoff bound is always 3.0001 after finding the
first feasible LP solution. You may think that I
have something wrong in my problem definition
and that 3.2 is actually not my optimal
solution, but the same cutoff bound of 3.0001
appears even when the initial columns gives a
integer (and obviously feasible) LP solution
with value equal to 3.2. It is somehow normal?<br>
</div>
</div>
</div>
</blockquote>
</span> Do you activate your pricer before calling SCIP
solve? If not, SCIP might detect that the objective value
of each solution will always be a multiple of some number,
for example 0.2. In that case, if a solution with value
3.2 was found, SCIP would set a cutoff bound of 3.0 + eps,
which would be exactly 3.0001. But this should not happen
if a pricer is enabled. Perhaps you can check that
SCIPgetOrigObjscale() and SCIPgetTransObjscale() are both
1.0.<br>
<br>
Best,<br>
Gerald
<div>
<div class="h5"><br>
<br>
<blockquote type="cite">
<div dir="ltr">
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2015-03-09 18:43
GMT+01:00 Gerald Gamrath <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:gamrath@zib.de" target="_blank">gamrath@zib.de</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>Dear Christina,<br>
<br>
it should not be a problem if you do not
set a lowerbound. Just to be sure, you
could set it to -SCIPinfinity().<br>
<br>
So we will need to investigate your
problem further. Could you send me a log
file (including statistics)?<br>
<br>
About the integer LP solutions: This
should automatically be done by the
simplerounding heuristic. Did you perhaps
disable the heuristic by accident?<br>
<br>
Best,<br>
Gerald
<div>
<div><br>
<br>
On 06.03.2015 17:08, Cristina Núñez
del Toro wrote:<br>
</div>
</div>
</div>
<div>
<div>
<blockquote type="cite">
<div dir="ltr">
<div>
<div>Dear Gerald,<br>
<br>
</div>
thank you for you response. <br>
<br>
<br>
</div>
<div>About 2) yes, I am sure that
pricing is performed at this node,
and 3) I start the B&P with a
with a set of initial variables
that gives a feasible primal
solution to the integer problem.
Both, initial and priced variables
are marked as removable and all
constraints are marked as
modifiable. <br>
<br>
About 1), I think this could be
actually the problem. I do not
compute the lower bound at any
point. I just followed the
binpacking example to create my
own implementation but I missed
this issue. In fact, I also
noticed that whenever an integer
LP solution gets into the pricing
callback, scip do not update the
best upper bound in case of
promising one. I read a previous
email about this issue and
recommended to use
SCIPupdateCutoofbound() and/or
SCIPsetObjlimit(). However, what I
am more concerned about why this
integral and feasible solution is
not stored as a Primal bound of
the original Integer Master
Problem thant setting a new
cuttoffbound. If you can help me
explaining me a little bit more
about this because I'm find myself
quite lost with that.<br>
</div>
<div>Best regards,<br>
</div>
<br>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2015-03-04
19:35 GMT+01:00 Gerald Gamrath <span
dir="ltr"><<a
moz-do-not-send="true"
href="mailto:gamrath@zib.de"
target="_blank">gamrath@zib.de</a>></span>:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div text="#000000"
bgcolor="#FFFFFF"> Dear
Christina,<br>
<br>
sorry for the late reply, but
we were quite busy in the last
weeks.<br>
<br>
There might be different
reasons for this behavior.<br>
<br>
1) Does your pricing callback
compute a lower bound and sets
the lowerbound pointer
accordingly? If this is higher
than the cutoff bound, the
node will be cut off.<br>
<br>
2) Perhaps the propagation
already detected
infeasibility? Are you sure
that you perform pricing at
this node?<br>
<br>
3) Are all your variables
created by pricing and all
constraints marked to be
modifiable? Otherwise, the
enforcement might also detect
infeasibility of an
unmodifiable constraint.<br>
<br>
Best,<br>
Gerald<br>
<br>
<div>Am 19.02.2015 um 15:27
schrieb Cristina Núñez del
Toro:<br>
</div>
<blockquote type="cite">
<div>
<div>
<div dir="ltr">
<div>
<div>
<div>
<div>
<div>
<div>
<div>Dear all,<br>
<br>
</div>
I am currently
implemented a
Branch&Price
algorithm. For
my problem, I
have 3 types
of variables,
say "x","y"
and "z". I
have just
finished my on
branching rule
that implies
to only branch
on the "z"
variables.
Apparently,
everything
goes ok; I
mean,
everytime SCIP
enters to the
branchexeclp
routine, it
looks for the
most
fractional "z"
variable and
do branch on
it. However, I
have noticed
that a certain
point of the
algorithm,
after
finishing the
pricing loop,
SCIP "skips"
(sorry for the
joke) the
branching
phase (the
node is cutted
off/pruned), I
mean, it does
not enter to
any branching
callback
method and
goes directly
to the handler
constraint to
propagate
another node.
As far I
understand,
this would be
of course a
normal
behaviour if,
after
finishing the
pricing stage
:<br>
<br>
</div>
a) the
objective
value of the
current LP is
greater or
equal than the
incumbent,<br>
b) the current
LP solution is
an integer
solution,<br>
</div>
c) the current
LP solution is
an integer
solution and
it is optimal.<br>
<br>
</div>
However, I found
a pruned node
with a
fractional LP
solution
(inluding some
"z" variables
with fractional
value) but with
the objective
value <span
lang="en"><span>strictly
lower than the
incumbent.<br>
<br>
</span></span></div>
<span lang="en"><span>Is
there any
reason for
expecting
this? <br>
<br>
</span></span></div>
<span lang="en"><span>Thanks
in advances,<br>
<br>
</span></span></div>
<span lang="en"><span>Best
regards,<br>
</span></span>
<div>
<div>
<div>
<div>
<div>
<div>
<div>
<div><br>
<br>
-- <br>
<div>---<br>
Cristina Nuñez<br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
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<br>
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</blockquote>
<br>
</div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
<div>---<br>
Cristina Nuñez<br>
</div>
</div>
</blockquote>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
<div>---<br>
Cristina Nuñez<br>
</div>
</div>
</blockquote>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
<div class="gmail_signature">---<br>
Cristina Nuñez<br>
</div>
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</blockquote>
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