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https://issues.apache.org/jira/browse/SYSTEMML-259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15951362#comment-15951362
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Mike Dusenberry commented on SYSTEMML-259:
------------------------------------------
[~deron] Unfortunately, I think we need to look further at this. I tried
updating the {{nn}} library to remove the unneeded left-hand variables for test
functions with no returns, and I experienced a null pointer issue. I boiled it
down to the following small example.
{code}
func = function(int a) {
print(a)
}
func(3)
{code}
This snippet works as expected, which was initially surprising given that my
real example in the {{nn}} library was failing. I took a look at the explain,
and realized that this function was just being inlined, and thus was working
just fine.
{code}
# Memory Budget local/remote = 5496MB/140MB/140MB
# Degree of Parallelism (vcores) local/remote = 48/1/1
PROGRAM ( size CP/MR = 0/0 )
--MAIN PROGRAM
----GENERIC (lines 6-6) [recompile=false]
------CP print 3.SCALAR.INT.true _Var0.SCALAR.STRING
------CP rmvar _Var0
3
{code}
Adding a graph cut to force the compiler to keep the function invokes the issue.
{code}
func = function(int a) {
if(1==1){} # cut!
print(a)
}
func(3)
{code}
{code}
java.lang.NullPointerException
at
org.apache.sysml.parser.StatementBlock.validate(StatementBlock.java:599)
at
org.apache.sysml.parser.DMLTranslator.validateParseTree(DMLTranslator.java:141)
at org.apache.sysml.api.DMLScript.execute(DMLScript.java:589)
at org.apache.sysml.api.DMLScript.executeScript(DMLScript.java:351)
at org.apache.sysml.api.DMLScript.main(DMLScript.java:212)
Exception in thread "main" org.apache.sysml.api.DMLException:
java.lang.NullPointerException
at org.apache.sysml.api.DMLScript.executeScript(DMLScript.java:365)
at org.apache.sysml.api.DMLScript.main(DMLScript.java:212)
Caused by: java.lang.NullPointerException
at
org.apache.sysml.parser.StatementBlock.validate(StatementBlock.java:599)
at
org.apache.sysml.parser.DMLTranslator.validateParseTree(DMLTranslator.java:141)
at org.apache.sysml.api.DMLScript.execute(DMLScript.java:589)
at org.apache.sysml.api.DMLScript.executeScript(DMLScript.java:351)
... 1 more
Failed to run SystemML. Exit code: 1
{code}
Adding the dummy return variable works.
{code}
func = function(int a) {
if(1==1){}
print(a)
}
tmp = func(3)
{code}
{code}
PROGRAM ( size CP/MR = 0/0 )
--FUNCTIONS
----FUNCTION CALL GRAPH
------MAIN PROGRAM
--------.defaultNS::func
----FUNCTION .defaultNS::func [recompile=false]
------GENERIC (lines 3-3) [recompile=false]
--------CP print a.SCALAR.INT.false _Var1.SCALAR.STRING
--------CP rmvar _Var1
--------CP rmvar a
--MAIN PROGRAM
----GENERIC (lines 6-6) [recompile=false]
------CP extfunct .defaultNS func 1 1 3.SCALAR.INT.true tmp
3
{code}
Thoughts?
> If no return type specified, DML/PyDML function calls require an lvalue
> -----------------------------------------------------------------------
>
> Key: SYSTEMML-259
> URL: https://issues.apache.org/jira/browse/SYSTEMML-259
> Project: SystemML
> Issue Type: Improvement
> Components: APIs
> Reporter: Deron Eriksson
> Assignee: Deron Eriksson
> Priority: Minor
> Fix For: SystemML 1.0
>
>
> If a function is defined in DML or PyDML with no return type, and then this
> function is called, it requires an lvalue variable to be assigned the value
> returned from the function, even though no value is returned from the
> function.
> DML Example (assigning to z is required):
> {code}hello = function() {
> print('hi')
> }
> z = hello(){code}
> PyDML Example (assigning to z is required):
> {code}def hello():
> print('hi')
> z = hello(){code}
> DML Example (error: "function call needs to have lvalue (Quickfix: change it
> to 'tmpVar = hello(...)')"):
> {code}hello = function() {
> print('hi')
> }
> hello(){code}
> PyDML Example(error: "function call needs to have lvalue (Quickfix: change it
> to 'tmpVar = hello(...)')"):
> {code}def hello():
> print('hi')
> hello(){code}
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