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https://issues.apache.org/jira/browse/NUMBERS-156?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17340144#comment-17340144
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Matt Juntunen commented on NUMBERS-156:
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I've run some benchmarks and accuracy tests on {{SafeNorm}} vs the code above.
The approaches I tested are
* exact - BigDecimal with MathContext.DECIMAL128
* unsafe - direct, unchecked computation with doubles
* safe - current {{SafeNorm}} code
* herbert - the code above
The accuracy results are below for 100,000 vectors of length 3. The "non-finite
count" column indicates how many computed results were not finite.
|| Name || ulp error mean || ulp error std dev || non-finite count ||
| exact | 0.0 | 0.0 | 0 |
| unsafe | 5578.94225972039 | 18.57625771920449 | 9803 |
| safe | 0.01339 | 4.2343109585731824E-5 | 0 |
| herbert | 2.0E-4 | 6.324586943350534E-7 | 0 |
Here are the performance results for the same number of inputs:
||Benchmark||Mode||Cnt||Score||Error||Units||
|NormsPerformance.exact|avgt|5|1220297639.200 |± 356780909.362 |ns/op|
|NormsPerformance.herbert|avgt|5|2477818.076 |± 256183.380 |ns/op|
|NormsPerformance.safe|avgt|5|3116261.568 |± 603776.022 |ns/op|
|NormsPerformance.unsafe|avgt|5|983066.792 |± 103953.143 |ns/op|
_Conclusion_
The code Alex has above is far more accurate and moderately more performant
than {{SafeNorm}}. I suggest we replace the existing {{SafeNorm}}
implementation with this new code. The only question is how do we structure the
API. Perhaps we could create a {{Norms}} class with methods for L!, L2, and
LInf norms and overloads for 1D, 2D, 3D, and ND vectors?
> SafeNorm 3D overload
> --------------------
>
> Key: NUMBERS-156
> URL: https://issues.apache.org/jira/browse/NUMBERS-156
> Project: Commons Numbers
> Issue Type: Improvement
> Reporter: Matt Juntunen
> Priority: Major
>
> We should create an overload of {{SafeNorm.value}} that accepts 3 arguments
> to potentially improve performance for 3D vectors.
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