44 lines
1.8 KiB
Markdown
44 lines
1.8 KiB
Markdown
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# Auto initialization for in-place operations
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## Status
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REJECTED
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Discussed by: Paul Dubs, Alex Black, raver119 on 25. November 2019
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## Context
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Some operations work in-place on the inputs that they are given in ND4J, but in SameDiff the same operations will
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generate an array from a given shape. Examples for this include `BernoulliDistribution`, and other random ops, that
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effectively initialize the array that they are given.
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From a consistency point of view, it would be nice if both API's would support both ways of using those ops.
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## Decision
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We introduce an option to mark inputs as `inPlace = true` to make it clear that this input is going to be changed
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in-place. In addition we introduce an option `supportsInPlaceInit = true` to mark an input as initialize-able. If the
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`supportsInPlaceInit` option is enabled, two signatures for the Op will be created, one that takes an input, and one
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that takes the appropriate shape and data type information in its stead.
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## Consequences
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### Advantages
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* We get support for both in-place and initialization use-cases
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* Support for this use-case is explicitly defined in the DSL instead of implicit support by the code generator
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### Disadvantages
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* Codegen becomes more complex, as it requires us to generate more signatures
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## Reasons for Rejection
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This feature would only come in handy on legacy ops. However, those ops will not be exposed to frontend languages
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anymore starting from the next release.
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For the ops that replace them ("Custom Ops"), it is *always* possible to pass an output array, when used in NDArray
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programming mode. Thereby making the in-place initialization support a side-effect of that general design.
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For support of both `op(out)` and `op(dataType, shape)` see ADR 0005 "Optional parameters and signatures".
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