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MathGroup Archive 2004

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Re: Re: Linear Programming

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51049] Re: [mg51011] Re: [mg50977] Linear Programming
  • From: DrBob <drbob at bigfoot.com>
  • Date: Sat, 2 Oct 2004 03:19:18 -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> <8F126887-13F3-11D9-BCA4-000A95B4967A@mimuw.edu.pl>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

Where did you find that documentation? It's not in the Help article for NMinimize (version 5.0.1), and it's not in section 1.6.5 or 3.9.8 or A.9.4. Ah, I see... it's in the Advanced Documentation, where it really doesn't belong.

The basic template for calling NMinimize should reflect this info, at the top of the NMinimize help article. It affects the scope and usage of NMinimize in a very basic way.

Anyway, the message may be consistent, but it's not useful. If you know and remember that explanation from the Advanced Documentation, you'd probably never see the message anyway.

Bobby

On Sat, 2 Oct 2004 06:47:58 +0900, Andrzej Kozlowski <akoz at mimuw.edu.pl> wrote:

> *This message was transferred with a trial version of CommuniGate(tm) Pro*
> 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:
>
>> *This message was transferred with a trial version of CommuniGate(tm)
>> Pro*
>> 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} â?? 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
>>
>
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


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