Struct builders

[segeljakt]

The docs say:

Any struct whose fields are builders can also be used as a builder. This is used to build multiple results at the same time.

But, when I compile:

|source: vec[i32]|
    let final = for(source, {appender[i32], appender[i32]}, |sink, index, element|
        merge(sink, {element, element})
    );
    {result(final.$0), result(final.$1)}

I get:

[info] 15:49:09.591: Started weld_module_compile
[info] 15:49:09.594: Started parsing program
[info] 15:49:09.608: Done parsing program
[info] 15:49:09.608: Started compiling program
[debug] 15:49:09.611: After macro substitution:
|source:vec[i32]|
  (let final:?=(for(
    source:?,
    {appender[i32],appender[i32]},
    |sink:?,index:?,element:?|
      merge(sink:?,{element:?,element:?})
  ));{result(
    final.$0
  ),result(
    final.$1
  )})

[info] 15:49:09.612: Done compiling program
REPL: Compile error: Internal error: Merge called on non-builder
>>>

My expectation was that you could merge structs which only contain builders, and also call result on structs which only contain builders.

[sppalkia]

Try changing your merge to be {merge(sink.$0, element), merge(sink.$1, element)} (you need to explicitly specify the merge for each builder in the struct).

On Fri, Jul 19, 2019 at 6:50 AM segeljakt notifications@github.com wrote:

The docs say:

Any struct whose fields are builders can also be used as a builder. This is used to build multiple results at the same time.

But, when I compile:

|source: vec[i32]| let final = for(source, {appender[i32], appender[i32]}, |sink, index, element| merge(sink, {element, element}) ); {result(final.$0), result(final.$1)}

I get:

[info] 15:49:09.591: Started weld_module_compile [info] 15:49:09.594: Started parsing program [info] 15:49:09.608: Done parsing program [info] 15:49:09.608: Started compiling program [debug] 15:49:09.611: After macro substitution: |source:vec[i32]| (let final:?=(for( source:?, {appender[i32],appender[i32]}, |sink:?,index:?,element:?| merge(sink:?,{element:?,element:?}) ));{result( final.$0 ),result( final.$1 )})

[info] 15:49:09.612: Done compiling program REPL: Compile error: Internal error: Merge called on non-builder

My expectation was that you could merge structs which only contain builders, and also call result on structs which only contain builders.

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-- Shoumik

[segeljakt]

Ok, thanks, makes sense :)

I have another question regarding builders. What happens internally in Weld when you swap the field positions of two builders? E.g:

|source: vec[i32]|
    let final = for(source, {appender[i32], appender[i32]}, |sink, index, element|
        {merge(sink.$1, 1), merge(sink.$0, 0)}
    );
    {result(final.$0), result(final.$1)}

[sppalkia]

That's fine as long as you maintain their linearity property (i.e., each builder should be consumed exactly once per control path) and the types of the swapped builders are the same if you're inside a for loop. We don't have a compile time check for this at the moment unfortunately (it's in the works though!)

On Fri, Jul 19, 2019 at 8:09 AM segeljakt notifications@github.com wrote:

Ok, thanks, makes sense :)

I have another question regarding builders. What happens internally in Weld when you swap the field positions of two builders? E.g:

|source: vec[i32]| let final = for(source, {appender[i32], appender[i32]}, |sink, index, element| {merge(sink.$1, 1), merge(sink.$0, 0)} ); {result(final.$0), result(final.$1)}

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-- Shoumik

[sppalkia]

Sorry, realized you asked what happens internally: you can think of the builder as a C struct, so swapping them within a struct will effectively swap the struct values.

On Fri, Jul 19, 2019 at 8:46 AM Shoumik Palkar shoumikpalkar@gmail.com wrote:

That's fine as long as you maintain their linearity property (i.e., each builder should be consumed exactly once per control path) and the types of the swapped builders are the same if you're inside a for loop. We don't have a compile time check for this at the moment unfortunately (it's in the works though!)

On Fri, Jul 19, 2019 at 8:09 AM segeljakt notifications@github.com wrote:

Ok, thanks, makes sense :)

I have another question regarding builders. What happens internally in Weld when you swap the field positions of two builders? E.g:

|source: vec[i32]| let final = for(source, {appender[i32], appender[i32]}, |sink, index, element| {merge(sink.$1, 1), merge(sink.$0, 0)} ); {result(final.$0), result(final.$1)}

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/weld-project/weld/issues/464?email_source=notifications&email_token=AAKMEY776IQO2UN2HVRVQHTQAHKLVA5CNFSM4IFGFODKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD2L5DZQ#issuecomment-513266150, or mute the thread https://github.com/notifications/unsubscribe-auth/AAKMEY6NPDYUVNSAC2266NTQAHKLVANCNFSM4IFGFODA .

-- Shoumik

-- Shoumik