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From "Alex (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MATH-832) Brent solver calculates incorrect root (namley Double.MAX_VALUE)
Date Tue, 24 Jul 2012 20:58:35 GMT
```
[ https://issues.apache.org/jira/browse/MATH-832?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alex updated MATH-832:
----------------------

Description:
Wolfram-Alpha-Solution:
http://www.wolframalpha.com/input/?i=min+100*sqrt%28x%29%2B1000000%2Fx%2B10000%2Fsqrt%28x%29+with+x%3E0

Java-Input:{code:title=Test.java|borderStyle=solid}
int startValue1 = 100 + 1000000 + 10000;
int startValue2 = 100;

System.out.println(
(new BrentSolver()).solve(Integer.MAX_VALUE, new UnivariateFunction() {
@Override
public double value(double x) {
return 100/(2*Math.sqrt(x)) - 1000000/Math.pow(x,2) - 10000/(2*Math.pow(x,(double)
3/2));
}
}, 1/Double.MAX_VALUE, Double.MAX_VALUE, startValue1)
);

System.out.println(
(new BrentSolver()).solve(Integer.MAX_VALUE, new UnivariateFunction() {
@Override
public double value(double x) {
return 100/(2*Math.sqrt(x)) - 1000000/Math.pow(x,2) - 10000/(2*Math.pow(x,(double)
3/2));
}
}, 1/Double.MAX_VALUE, Double.MAX_VALUE, startValue2)
);{code}

Java-Output:{code:borderStyle=solid}
804.9355821866686
1.7976931348623157E308 (= Double.MAX_VALUE){code}

was:
Wolfram-Alpha-Solution:
http://www.wolframalpha.com/input/?i=min+100*sqrt%28x%29%2B1000000%2Fx%2B10000%2Fsqrt%28x%29+with+x%3E0

Java-Input:{code:title=Test.java|borderStyle=solid}
int startValue1 = 100 + 1000000 + 10000;
int startValue2 = 100;

System.out.println(
(new BrentSolver()).solve(Integer.MAX_VALUE, new UnivariateFunction() {
@Override
public double value(double x) {
return 100/(2*Math.sqrt(x)) - 1000000/Math.pow(x,2) - 10000/(2*Math.pow(x,(double)
3/2));
}
}, 1/Double.MAX_VALUE, Double.MAX_VALUE, startValue1)
);

System.out.println(
(new BrentSolver()).solve(Integer.MAX_VALUE, new UnivariateFunction() {
@Override
public double value(double x) {
return 100/(2*Math.sqrt(x)) - 1000000/Math.pow(x,2) - 10000/(2*Math.pow(x,(double)
3/2));
}
}, 1/Double.MAX_VALUE, Double.MAX_VALUE, startValue2)
);{code}

Java-Output:{code:title=Test.java|borderStyle=solid}
804.9355821866686
1.7976931348623157E308 (= Double.MAX_VALUE){code}

> Brent solver calculates incorrect root (namley Double.MAX_VALUE)
> ----------------------------------------------------------------
>
>                 Key: MATH-832
>                 URL: https://issues.apache.org/jira/browse/MATH-832
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.0
>         Environment: Netbeans 7.1.2
>            Reporter: Alex
>   Original Estimate: 0.75h
>  Remaining Estimate: 0.75h
>
> Wolfram-Alpha-Solution:
> http://www.wolframalpha.com/input/?i=min+100*sqrt%28x%29%2B1000000%2Fx%2B10000%2Fsqrt%28x%29+with+x%3E0
> Java-Input:{code:title=Test.java|borderStyle=solid}
> int startValue1 = 100 + 1000000 + 10000;
> int startValue2 = 100;
> System.out.println(
>     (new BrentSolver()).solve(Integer.MAX_VALUE, new UnivariateFunction() {
>     @Override
>     public double value(double x) {
>         return 100/(2*Math.sqrt(x)) - 1000000/Math.pow(x,2) - 10000/(2*Math.pow(x,(double)
3/2));
>     }
> }, 1/Double.MAX_VALUE, Double.MAX_VALUE, startValue1)
> );
> System.out.println(
>     (new BrentSolver()).solve(Integer.MAX_VALUE, new UnivariateFunction() {
>     @Override
>     public double value(double x) {
>         return 100/(2*Math.sqrt(x)) - 1000000/Math.pow(x,2) - 10000/(2*Math.pow(x,(double)
3/2));
>     }
> }, 1/Double.MAX_VALUE, Double.MAX_VALUE, startValue2)
> );{code}
> Java-Output:{code:borderStyle=solid}
> 804.9355821866686
> 1.7976931348623157E308 (= Double.MAX_VALUE){code}

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