Stage

stage NAME [ '[' N ']' ] : kind;

A stage is where time passes, and where a run takes it.

Kind	Servers	Unit of run's work
fifo(c)	c, one job each	clock time at rate 1
ps(φ)	all jobs at once	clock time, at rate φ(present)/present per job
delay	infinite	clock time at rate 1

The clock has no unit of its own: costs in seconds run in seconds. A stage that runs iterations, whose work is tokens, is an engine on a device, written engine NAME on DEVICE { … }.

fifo

fifo [ ( c ) ]

Argument	Type	Default	Description
c	const, a positive integer	1	Servers. Jobs are served in arrival order.

ps

ps ( expr )

Argument	Type	Moment	Description
expr	expr	Ps	Total throughput φ(present), shared equally by the jobs present. The context variable present is the number of jobs.

stage svc : ps(1);

(examples/single-turn/ps.sq, M/G/1-PS.) A ps stage some run holds together with another is served by the program's share instead: its jobs are flows, not an equal split.

delay

delay

Every job proceeds at rate 1 with no waiting. It is ps(present), each of present jobs at present/present, and links to the same IR: the run, the drawing and the Lean model read the two spellings alike.

Examples

A complete program:

fn main() {
  stage svc : fifo;
  workload {
    arrive poisson(0.5);
  }
  server {
    set t0 = now;
    run svc (cost(svc, ~exp(1)));
    observe response = now - t0;
  }
}

Save as model.sq, then run:

serq run model.sq --horizon 10

See also

Engine, run, context variables, pyserq.Stage.