[6.0.0] Conversion from Long-encoded nBits representation to BigInt and back #962
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@kushti, I suggest to add these operations as methods of SGlobal (i.e. in SGlobalMethods) |
kushti
changed the title
moved, also, the PR is finalized now, please review. If you think anything is not tested, please specify what exactly, and so I will be able to add tests. |
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IMO, the most important tests are those in LanguageSpecification, more specifically using verifyCases method.
When they are done, not only full coverage is ensured, but also cost profiling can be done.
I suggest to test these new operations as two separate property()
| @@ -695,6 +695,20 @@ trait SigmaDslBuilder { | |||
| */ | |||
| def groupGenerator: GroupElement | |||
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| /** | |||
| * @return big integer provided as input approximately encoded using NBits, | |||
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A bit confusing comment, says "@return big integer" while the actual return type is Long.
| groupGeneratorMethod, | ||
| xorMethod | ||
| ) | ||
| private lazy val EnDecodeNBitsCost = FixedCost(JitCost(5)) // the same cost for nbits encoding and decoding |
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The cost is too low. And encoding is cheaper than decoding (because of array creation).
There is a profiler in LSV5 (see the comments and afterAll method).
I suggest at least 2 for encoding and 40 for decoding.
| @@ -175,6 +176,14 @@ class CSigmaDslBuilder extends SigmaDslBuilder { dsl => | |||
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| override def groupGenerator: GroupElement = _generatorElement | |||
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| def encodeNbits(bi: BigInt): Long = { | |||
In this PR, two new methods, Global.encodeNbits() and Global.decodeNbits() are introduced, to support conversion from NBits-encoded numbers to big integers and back
Among new tests Bitcoin PoW check example can be found.
close #675
TODO: en/decodeNBits likely should work with UnsignedBigInt , which will be done in UnsignedBigInt PR, or during merging this into v6.0.0 with UnsignedBigInt impl being merged, depending on merging order