Replace VarInt.getLength with Protobuf's branchless implementation #36959
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Summary of ChangesHello @sjvanrossum, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request focuses on optimizing the calculation of variable-length integer (VarInt) encoding lengths within the Highlights
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| // Log2 is performed using a bit counting instruction. | ||
| // Multiplication by 9 is performed using a 3-bit left shift and add. | ||
| // Division by 64 is performed using a 6-bit right shift. | ||
| return ((Integer.SIZE * 9 + (1 << 6)) - (Integer.numberOfLeadingZeros(v) * 9)) >>> 6; |
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could we instead call the public static methods on CodedOutputStream?
ie CodedOutputStream.computeUInt32SizeNoTag here and 64 below?
Then if further improvements are made we get them for free.
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I didn't realize core depends on protobuf, I thought that everything had moved to extensions/protobuf.
I've imported CodedOutputStream from the unvendored com.google.protobuf package, but would it make more sense to pull it in from org.apache.beam.vendor.grpc.v1p69p0.com.google.protobuf?
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Since we're not leaking an object just calling the function, I think the unvendored package is fine. But looping in @Abacn to confirm.
sdks/java/core/src/main/java/org/apache/beam/sdk/util/VarInt.java
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Need to fix spotless also |
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See https://github.com/protocolbuffers/protobuf/blob/0a2f7757e38b07c2e40c5c885a7100e8c16eb40f/java/core/src/main/java/com/google/protobuf/CodedOutputStream.java#L700 for details.
This change copies Protobuf's branchless implementation for varint length calculation.
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