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https://issues.apache.org/jira/browse/NUMBERS-163?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17362908#comment-17362908
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Alex Herbert commented on NUMBERS-163:
--------------------------------------
{quote}There is (surprisingly perhaps) no performance loss (on the contrary,
for the simple cases).
{quote}
Thanks for testing. I have no other issues with the builder type API and that
is more flexible. Maintaining the static methods when performance is no
different is not necessary.
{quote}As far as making LinearCombination itself implement DoubleSupplier, I do
not see the utility.
{quote}
You can have different implementations of LinearCombination. dot2s is a 2-fold
precision algorithm. The generic extension is the dotK family for k-fold
precision. There is also the unlimited precision method (within the bounds of
the range of a double).
But this would also work for the accumulator class you are describing. The
accumulator can have sub-class implementations.
The algorithm should be specified in the constructor:
{code:java}
double x1 = LinearCombination.of(LinearCombination.DOT_2S)
.add(1e300, 1)
.add(1e100, 1)
.add(1, 1)
.add(-1e300, 1)
.add(-1e100, 1)
.getAsDouble();
assert x1 == 1;
{code}
I think this fails for the dot2s algorithm. But it would work for DOT_3
algorithm.
This would allow code to switch the accuracy by just putting in a different
enum specified algorithm.
> Summation and LinearCombination Accumulators
> --------------------------------------------
>
> Key: NUMBERS-163
> URL: https://issues.apache.org/jira/browse/NUMBERS-163
> Project: Commons Numbers
> Issue Type: New Feature
> Reporter: Matt Juntunen
> Priority: Major
> Time Spent: 20m
> Remaining Estimate: 0h
>
> It would be useful to have simple accumulator classes in {{Summation}} and
> {{LinearCombination}} to perform extended precision operations on arbitrary
> collections of values without requiring conversion to {{double[]}}. Ex:
> {code:java}
> Summation.Accumulator sum= Summation.accumulator(1d);
> sum.add(x)
> .add(y)
> .add(z)
> .add(w);
> double sumResult = sum.get();
> LinearCombination.Accumulator comb = LinearCombination.accumulator(1d);
> comb.add(x, scale)
> .add(y, scale)
> .add(z, scale)
> .add(w, scale);
> double combResult = comb.get();
> {code}
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