Matthias Boehm created SYSTEMML-2169: ----------------------------------------
Summary: Spark nary cbind/rbind with broadcasts Key: SYSTEMML-2169 URL: https://issues.apache.org/jira/browse/SYSTEMML-2169 Project: SystemML Issue Type: Task Reporter: Matthias Boehm The introduction of nary cbind and rbinds in SYSTEMML-1986 added support for operations like {{E = cbind(A,B,C,D)}} which concatenates the matrices A, B, C, D column-wise without the need for intermediates as requires by traditional binary cbind operations ({{cbind(cbind(cbind(A,B),C),D)}}). SystemML also provides rewrites to automatically collapse chains of cbind or rbind operations into their nary counter-parts. However, for distributed spark operations, the binary cbind is still much better optimized than the nary operation, which only provides a general case operation based on repartition joins. This tasks aims to address this by extending {{BuiltinNarySPInstruction}} at runtime level. Given the unlimited number of inputs, this runtime approach seems more appropriate than dedicated physical operations at compiler level. In detail, we need to evaluate if a subset of input fits into the broadcast budget, and if so provide alternative code path for nary cbind/rbind operations with broadcast joins. Note that distributed codegen operations have a similar characteristics of unlimited inputs and already leverage broadcast variables when possible. Hence, we can probably use a similar approach as done in {{SpoofSPInstruction}}. -- This message was sent by Atlassian JIRA (v7.6.3#76005)