Math Forum / Mathematics / Operations Research / January 2008

According to the announcement on Dash Optimization web page, Dash
Optimziation acquired by  Fair Isaac
http://www.dashoptimization.com/home/services/news/news_fairisaac.html
is this good or bad for Xpress-MP users?.. Frankly speaking (and this

Consider the following linear fractional program P1.
P1: Min (a*x+b*y)/(x+y+1)
s.t. x,y>=0 and c*x+d*y<e
where x,y are real positive variables and a,b,c,d,e are real

Hello, profs here.
I am programming in Java to call the Cplex API. But when I check back
the ".lp" file generated, I cannot find some of the constraints I
added

Does any one have an idea for convex relaxation of
f(x_1,...x_n)=
sum_k log ((sum_i x_i*a_ik )/(sum_i xi)) ?
where a's are constants and x's are variables? The tighter the better!

which volume cuts hyperplane <d,x> = 0 from simplex (sum xi = 1,
xi>=0) (in n-dimensional space)?
(upper one, i.e. scalar multiplication<d,x> is greater than zero)
Thank you in advance, D.

let q is known vector of same length as vectors s
does anyone know what is
P{sum(<q,s>)>0 | s[i]>=0, sum(s[i])=1}
equal to?

I'm attempting to solve a general quadratic programm
min F = .5 * x' * H * x + G * x
with G positiv definit and either inequality constraints or constraint on the
variables.

Good day,
I'd like to ask you guys what fields are just new to the application
of OR modelling.  I need to do a thesis for the graduate program I am
about next year and would like to start reading some stuff.  About 2

I have two questions about linear programs:
1)
I wonder whether there is any known facts (either formally, or
experimentally) about what makes an LP problem easy, or not. By words

I would like some opinion:
Is there any use/application of LP problem which is infeasible and/or
unbounded?

I can't seem to get my head round the expressibility of linear
programming. I am trying to write a timetabling program using the
integer programming approach.
I have

Hi all, I have had some basic training in optimization, but I could
use some help conceptualizing  the following problem:
Two teams are picking players to play a game, such as basketball.
Each team picks 5 players out of a pool of 76 total.

i am a university student. we found that our exams are always clashing
and therefore it takes long time(one and half month) to finish a
semester exam.
i have learned integer programming. i thought that there should be a

I'm wondering if it is possible to linearize a sum of products of
integer variables with continuous ones.
Let me be preciser:
Let x_i (i = 1,...,n) be continuous variables in [0,1].

My problem is a combination of LP, SOCP and SDP constraints. The SDP
portion is very small though (only one 2x2 positive definite
constraint). If I want to write the whole problem in SDP form it will
be very inefficient. So I need some help on how to feed the problem to