[jira] [Created] (BEAM-4765) Use explicit receivers for method invocations.

["Robert Burke (JIRA)" <ji...@apache.org>]

Robert Burke created BEAM-4765:
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             Summary: Use explicit receivers for method invocations. 
                 Key: BEAM-4765
                 URL: https://issues.apache.org/jira/browse/BEAM-4765
             Project: Beam
          Issue Type: Sub-task
          Components: sdk-go
            Reporter: Robert Burke
            Assignee: Robert Burke


Presently we use the "receiverless" variant to reflectively  get methods on structs in graph/fn.go, but it's possible to get a version with an explicit receiver as well. Unfortunately due to reflect method invocation overhead, calls to functions sourced this way have significant overhead.
 
This task represents a TODO in graph/fn.go
 
I wrote a benchmark (to be submitted) that explores the approaches:
BenchmarkStructMethodCalls/ReflectCallNoReceiver-12         5000000       377 ns/op      56 B/op       3 allocs/op
BenchmarkStructMethodCalls/ReflectCallWithReceiver-12       5000000       297 ns/op      48 B/op       2 allocs/op
BenchmarkStructMethodCalls/DirectWithReceiver-12             300000000         3.58 ns/op       0 B/op       0 allocs/op
BenchmarkStructMethodCalls/TypeAssertedWithReceiver-12       300000000         3.58 ns/op       0 B/op       0 allocs/op
BenchmarkStructMethodCalls/ReflectXCallWithReceiver-12       5000000       345 ns/op     112 B/op       5 allocs/op
BenchmarkStructMethodCalls/ShimedCallWithReceiver-12         20000000        69.3 ns/op      40 B/op       3 allocs/op
BenchmarkStructMethodCalls/ShimedCall1x1-12                 100000000        20.7 ns/op       8 B/op       1 allocs/op
 

Note: Some of these represent the compiler assisting the explicit calls, due to the micro benchmarking: DirectWithReceiver, and TypeAssertedWithReceiver in particular. 
 
ShimedCallWithReceiver represents the "typical" invocation path with a reflectx.Func.Call([]interface{})  invocation, while ShimedCall1x1 is the arity specialized version.
Note: This be a breaking change to anyone using the reflectx & graph packages on structural DoFn outside of the project. However, we don't presently make a stability guarantee on these internal package details, so that's probably OK.
 
 



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