Impact of Changing a File or Node

The CLI Program vsc - Vov Show Consequences

The command line program vsc generates an "Impact Analysis" report to estimate the consequences of changing a particular file or node.

The name of this program was created to be the acronym for "Vov Show Consequences."

Impact of a Node Changing

When downstream jobs depend on an input file that changes, the downstream jobs must be run again. As they run, they can cause files to change which in turn trigger a need to run other jobs, and so on. All this downstream effect based on the dependency graph is known as the down-cone of a node.

The impact of a node is the total expected duration of the jobs that are rerun in its down-cone.

FlowTracer uses impact analysis to schedule jobs in the critical path ahead of the other jobs.

For efficiency reasons, FlowTracer uses an approximate calculation of the impact. In particular, for the purpose of job scheduling, all jobs with duration less than 5 seconds, are categorized as a "large" impact, thus saving the computation of a full and accurate impact.

vsc

This scripts performs "Impact Analysis" with VOV.

Description


vsc: Usage Message
  
  DESCRIPTION:
       This scripts performs "Impact Analysis" with VOV.
       It shows the possible consequences of changing something
       in the design.  In general, the consequences are that all 
       dependent jobs must be executed again. 
  
       The report is a worst-case analysis, in the sense that
       it is assumed that changes will propagate through all barriers.
       (For an explanation of barriers, see clevercopy).
  
  USAGE:
       % vsc [options] <node_descriptor> ...
       
       where the node descriptor is either the name of a file
       or the VovId of a node in the dependency graph.
  
  OPTIONS:     
       -help            -- This message.
  
  EXAMPLES:
       % vsc  a
       % vsc  00023456  00023457