       Re: Maximize with Integer constraints

• To: mathgroup at smc.vnet.net
• Subject: [mg78270] Re: Maximize with Integer constraints
• From: dh <dh at metrohm.ch>
• Date: Wed, 27 Jun 2007 05:29:12 -0400 (EDT)
• References: <f5qjmd\$669\$1@smc.vnet.net>

```
Hi,

that's a BUG! Wolfram should take note.

Mathematica screws up if you give real constrains for integers. Consider:

Maximize[{x,0<=x<=2},{x},Integers] gives {2,{x->2}}

Maximize[{x,0<=x<=2.},{x},Integers]gives {0.,{x->0}}

hope this helps, Daniel

sdw wrote:

> given entry #1:

>

>

> Maximize[

> {x1 + x2 + x3 + x4,

> Element[x1 | x2 | x3 | x4 , Integers] &&

> 0 <= x1 <= 5.6 &&

> 0 <= x2 <= 8.6 &&

> 0 <= x3 <= 9.7 &&

> 4.0 <= x4 <= 22.4 }, {x1, x2, x3, x4}]

>

> {4., {x1 -> 0, x2 -> 0, x3 -> 0, x4 -> 4}}

>

> note -  zeros for answers

> entry #2:

> Maximize[

> {x1 + x2 + x3 + x4,

> Element[x1 | x2 | x3 | x4 , Integers] &&

> 0 <= x1 <= 5.6 &&

> 0 <= x2 <= 8.6 &&

> 0 <= x3 <= 9.7 &&

> 4.1 <= x4 <= 22.4 }, {x1, x2, x3, x4}]

>

> {44., {x1 -> 5, x2 -> 8, x3 -> 9, x4 -> 22}}

>

> note good answers...

> only difference is 4.1 vs. 4 in constraints

> any ideas what is going on?

>

> thanks,

>

> sdw

>

>

```

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