[SYSTEMDS-2040] Repeated IPA function inling leads to replicated prints

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: SystemML 1.0.0
• Epic Link: Perftest and QA for SystemML 1.0 release
• Assignee: Matthias Boehm
• Reporter: Matthias Boehm
• Created: 08/Dec/17 03:05
• Updated: 09/Dec/17 01:34
• Resolved: 09/Dec/17 01:34

Description

Due to multiple rounds of IPA with a reused function call graph, the same function is inlined multiple times leading to replication of operations. For most types of operations, common-subexpression elimination removes this redundancy, but for prints and rand without seeds this leads to unnecessary redundancy. For example,

s = "Debug info: " + sum(matrix(1,10,10))
z = foo(s);

foo = function(String msg) return (boolean flag) {
    is_debug = TRUE;
    if( is_debug ) {
        print(msg); flag = TRUE;
    } 
    else {
        flag = FALSE;
    }   
}

generates the following runtime plan with 3 replicated prints

PROGRAM
--MAIN PROGRAM
----GENERIC (lines 1-2) [recompile=false]
------(19) dg(rand) [10,10,1000,1000,100] [0,0,0 -> 0MB], CP
------(20) ua(+RC) (19) [0,0,-1,-1,-1] [0,0,0 -> 0MB], CP
------(21) b(+) (20) [0,0,-1,-1,-1] [0,0,0 -> 0MB], CP
------(5) u(print) (21) [-1,-1,-1,-1,-1] [0,0,0 -> 0MB]
------(7) TWrite z [0,0,-1,-1,-1] [0,0,0 -> 0MB], CP
------(5) u(print) (21) [-1,-1,-1,-1,-1] [0,0,0 -> 0MB]
------(7) TWrite z [0,0,-1,-1,-1] [0,0,0 -> 0MB], CP
------(5) u(print) (21) [-1,-1,-1,-1,-1] [0,0,0 -> 0MB]
------(7) TWrite z [0,0,-1,-1,-1] [0,0,0 -> 0MB], CP