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Re: Re: Linear Programming
*To*: mathgroup at smc.vnet.net
*Subject*: [mg51047] Re: [mg51011] Re: [mg50977] Linear Programming
*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>
*Date*: Sat, 2 Oct 2004 03:19:11 -0400 (EDT)
*References*: <200409300852.EAA26529@smc.vnet.net> <200410010849.EAA11582@smc.vnet.net> <75C3A6C4-13A4-11D9-BCA4-000A95B4967A@mimuw.edu.pl> <opse7bhhb5iz9bcq@monster.cox-internet.com>
*Sender*: owner-wri-mathgroup at wolfram.com
Well, to me at least, the message sounds consistent with the following
fragment form the documentation:
In order for NMinimize to work, it needs a rectangular initial region
in which to start. This is similar to giving other numerical methods a
starting point or starting points. The initial region is specified by
giving each variable a finite upper and lower bound. This is done by
including a<=x<=b in the constraints, or {x,a,b} in the variables. If
both are given, the bounds in the variables are used for the initial
region, and the constraints are just used as constraints. If no initial
region is specified for a variable a, the default initial region of
-1<=x<=1 is used. Different variables can have initial regions defined
in different ways.
??
Andrzej
On 2 Oct 2004, at 02:13, DrBob wrote:
> No, disclaimers actually state something that's true. This error
> message tells a lie.
>
> Bobby
>
> On Fri, 1 Oct 2004 21:21:45 +0900, Andrzej Kozlowski
> <akoz at mimuw.edu.pl> wrote:
>
>> *This message was transferred with a trial version of CommuniGate(tm)
>> Pro*
>> It's a kind of disclaimer. If you do not know what they are good for
>> ask a lawyer ;-)
>>
>> You can avoid it by specifying some upper bounds for x and y, e.g.
>>
>>
>> NMinimize[{x + y, 100 >= x >= 5, 100 >= y >= 5,
>> 3*x >= 5*y, {x, y} $B":(B Integers}, {x, y}]
>>
>>
>> {14., {x -> 9, y -> 5}}
>>
>>
>>
>> Andrzej Kozlowski
>>
>> On 1 Oct 2004, at 17:49, DrBob wrote:
>>
>>> *This message was transferred with a trial version of CommuniGate(tm)
>>> Pro*
>>> This works, but it throws a meaningless error first:
>>>
>>> NMinimize[{x + y, x >= 5, y >= 5,
>>> 3*x >= 5*y, {x, y} \[Element] Integers},
>>> {x, y}]
>>>
>>> \!\(\*
>>> RowBox[{\(NMinimize::"incst"\), \(\(:\)\(\ \)\),
>>> "\<\"\\!\\(NMinimize\\)
>>> was unable to generate any
>>> initial points satisfying the inequality constraints \
>>> \\!\\({\\(\\(\\(\\(\\(\\(-3\\)\\)\\\\ \\(\\(Round[x]\\)\\)\\)\\) + \
>>> \\(\\(5\\\\ \\(\\(Round[y]\\)\\)\\)\\)\\)\\) ? 0}\\). The initial
>>> region \
>>> specified may not contain any feasible points. Changing the initial
>>> region or \
>>> specifying explicit initial points may provide a better solution. \
>>> \\!\\(\\*ButtonBox[\\\"More?\\\",
>>> ButtonStyle->\\\"RefGuideLinkText\\\", \
>>> ButtonFrame->None, ButtonData:>\\\"NMinimize::incst\\\"]\\)\"\>"}]\)
>>>
>>> {14., {x -> 9, y -> 5}}
>>>
>>> Perhaps somebody out there can explain why this error message is "a
>>> good thing"?
>>>
>>> Bobby
>>>
>>> On Thu, 30 Sep 2004 04:52:32 -0400 (EDT), Rodrigo Malacarne
>>> <malacarne at gmail.com> wrote:
>>>
>>>> Hi everybody,
>>>>
>>>> How can I insert a constraint in the following expression
>>>>
>>>> ConstrainedMin[x+y,{x>5,y>5,3x>5y},{x,y}]
>>>>
>>>> to find only integer results? Using the expression above I get
>>>>
>>>> {13.3333,{x->8.3333,y->5.}}
>>>>
>>>> but I want x to be an integer number.
>>>>
>>>> Cordially yours,
>>>> Rodrigo
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> DrBob at bigfoot.com
>>> www.eclecticdreams.net
>>>
>>
>>
>>
>>
>
>
>
> --
> DrBob at bigfoot.com
> www.eclecticdreams.net
>
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