[jira] [Commented] (SYSTEMML-1542) SystemML shouldn't enforce write statement need to be defined in all the if else branch

["Alok Singh (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SYSTEMML-1542?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15983734#comment-15983734 ] 

Alok Singh commented on SYSTEMML-1542:
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Here are the couple of solutions from the brainstorming session. 

1) Have the systemML returns NA_matrix . the concept of NA matrix would be similar to SQL like we have sparse matrix, dense matrix, empty matrix or NA_matrix . empty matrix return is also fine

2) user rewrite the DML so that there is no branch of if else and write statement. But I feel this is not the right solution since whatif there is the nested functions and write is in that nested function. it would be too much work for the end user to modify

3) parse the error message from dml and make appropriate decision in the downstream apps. However, sometimes systemML err msg can be very convulated and also I think having end user to change it is not good

4) we give stern warning saying that all the write are not there in all branches and we can also have a flag which when set will allow systemML to return empty matrix in case of no matrix in write in the if else clause.



> SystemML shouldn't enforce write statement need to be defined in all the if else branch
> ---------------------------------------------------------------------------------------
>
>                 Key: SYSTEMML-1542
>                 URL: https://issues.apache.org/jira/browse/SYSTEMML-1542
>             Project: SystemML
>          Issue Type: Story
>            Reporter: Alok Singh
>
> It seems like we have to define all the write cmd in all the possible systemML if else branch. 
> It could become very complicated for the nested function call to take this into account.
> I think systemML should automatically insert write(file, empty_matrix) if the all the branches of the DAG doesn't contains the write statement
> Note that in reference to the mlCtx, this pb manifest itself into big stack trace
> Note that this bug is also related to https://issues.apache.org/jira/browse/SYSTEMML-1422



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