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https://issues.apache.org/jira/browse/STATISTICS-82?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alex Herbert resolved STATISTICS-82.
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Resolution: Won't Fix
> Raise exception for integer overflow during statistic computation.
> ------------------------------------------------------------------
>
> Key: STATISTICS-82
> URL: https://issues.apache.org/jira/browse/STATISTICS-82
> Project: Commons Statistics
> Issue Type: Improvement
> Components: descriptive
> Reporter: Alex Herbert
> Priority: Minor
>
> Many statistics count the number of observations using a long. This limited
> computation to ~2^63 values.
> This is effectively impossible to achieve using single values. It is very
> easy to achieve using a combine:
> {code:java}
> final IntMean m = IntMean.of(2, 3);
> System.out.println(m.getAsDouble());
> for (int i = 0; i < 62; i++) {
> m.combine(m);
> }
> // n = 2^63 = -9223372036854775808
> System.out.println(m.getAsDouble());
> {code}
> Prints:
> {noformat}
> 2.5
> -0.5
> {noformat}
> Overflow can be detected in combine, e.g.
> {code:java}
> // throws ArithmeticException when n+m overflows
> n = Math.addExact(n, other.n)
> {code}
> However it is possible to create a statistic with a count very close to 2^63
> via combine and then increment it past 2^63 with single values. To avoid an
> expensive check at each addition, this case will have to detect overflow of n
> to negative during the final computation of the statistic.
> Raising an exception will guard against misuse. It is unlikely to affect any
> real use cases. Without an exception the user will have an invalid result
> which may cause downstream problems in the dependent code.
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