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java.lang.Object umontreal.iro.lecuyer.util.RatioFunction
public class RatioFunction
Represents a function computing a ratio of two values.
Constructor Summary | |
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RatioFunction()
Constructs a new ratio function. |
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RatioFunction(double zeroOverZero)
Constructs a new ratio function that returns zeroOverZero for the special case of 0/0. |
Method Summary | |
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double |
evaluate(double... x)
Computes the function g(x) for the vector x. |
double |
evaluateGradient(int i,
double... x)
Computes ∂g(x)/∂xi, the derivative of g(x) with respect to xi. |
int |
getDimension()
Returns d, the dimension of the function computed by this implementation. |
double |
getZeroOverZeroValue()
Returns the value returned by evaluate in the
case where the 0/0 function is calculated. |
void |
setZeroOverZeroValue(double zeroOverZero)
Sets the value returned by evaluate for
the undefined function 0/0 to zeroOverZero. |
Methods inherited from class java.lang.Object |
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equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public RatioFunction()
public RatioFunction(double zeroOverZero)
getZeroOverZeroValue
method for more information.
The default value of zeroOverZero is Double.NaN.
zeroOverZero
- the value for 0/0.Method Detail |
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public double getZeroOverZeroValue()
evaluate
in the
case where the 0/0 function is calculated.
The default value for 0/0 is Double.NaN.
Generally, 0/0 is undefined, and therefore associated with the Double.NaN constant, meaning not-a-number. However, in certain applications, it can be defined differently to accomodate some special cases. For exemple, in a queueing system, if there are no arrivals, no customers are served, lost, queued, etc. As a result, many performance measures of interest turn out to be 0/0. Specifically, the loss probability, i.e., the ratio of lost customers over the number of arrivals, should be 0 if there is no arrival; in this case, 0/0 means 0. On the other hand, the service level, i.e., the fraction of customers waiting less than a fixed threshold, could be fixed to 1 if there is no arrival.
public void setZeroOverZeroValue(double zeroOverZero)
evaluate
for
the undefined function 0/0 to zeroOverZero.
See getZeroOverZeroValue
for more information.
zeroOverZero
- the new value for 0/0.public int getDimension()
MultivariateFunction
getDimension
in interface MultivariateFunction
public double evaluate(double... x)
MultivariateFunction
evaluate
in interface MultivariateFunction
x
- a vector
x.
public double evaluateGradient(int i, double... x)
MultivariateFunction
evaluateGradient
in interface MultivariateFunction
i
- the variable to derive with respect to.x
- a vector
x.
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