RFR: 8306732: TruncatedSeq::predict_next() attempts linear regression with only one data point

[Thomas Schatzl]

On Mon, 24 Apr 2023 11:51:06 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> TruncatedSeq::predict_next() attempts linear regression with only one data point, this leads to a division by zero. (There are infinit many linear functions that fit equally well for a single point).
> 
> I suggest we do what we do for the zero points case, namely pick one of the linear functions.
> 
> For zero points the current version picks `y = 0 + 0*x` and the suggestion is that for one point `P` the function `y = P_y + 0*x` is picked.
> 
> Tested for ZGC tier1-7 on Oracle supported platforms. Only ZGC use TruncatedSeq::predict_next()

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/13614#pullrequestreview-1399637905