This is a development repository. The current release, PDQ 6.2.0, has its own repository with separate download and installation instructions.
PDQ is a library of functions for solving queueing-network models of systems of resources such as, distributed computer systems, manufacturing systems, and packet networks. PDQ models can be written optionally in a variety of conventional programming languages. The book Analyzing Computer System Performance with Perl::PDQ presents example applications for computer system performance analysis written in Perl. Another example below is written in Python.
Overview: What is PDQ?
Languages:
This release only supports the C language
(the native language of the PDQ library) and the very popular
R statistical language.
Example PDQ models in R can be found in the pdq-qnm-pkg/interfaces/R/pdq/demo/ directory.
The migration of Python from 2 to 3 has introduced maintenance complications for PDQ. Python 3 may eventually be accommodated in future PDQ releases.
Perl maintenance has officially ended with PDQ release 6.2.0 in order to remain compatible with the 2nd edition of the Perl PDQ book (2011).
Platforms: Linux, MacOS, Windows
Maintainers: Neil Gunther and Paul Puglia
Contributors: Denny Chen, Phil Feller, Neil Gunther, Peter Harding, Paul Puglia, Sam Zallocco
License: PDQ is distributed as OSS under the MIT license.
Synopsis: PDQ library functions
Example:
The following PDQ code, written in R, is a model of an AWS cloud application
implemented using the CreateMultiNode function along with the new MSC option for solving a
multiserver queue that services a finite number of user requests. You can read the background
to this PDQ model in the paper entitled:
Linux-Tomcat Application Performance on Amazon AWS.
library(pdq)
requests <- 400; # load due to mobile users
threads <- 300; # active tomcat server threads
stime <- 0.444; # measured service time (seconds)
Init("AWS Tomcat Model")
CreateClosed("Requests", BATCH, requests, 0.0)
CreateMultiNode(threads, "Threads", MSC, FCFS)
SetDemand("Threads", "Requests", stime)
SetWUnit("Reqs")
Solve(EXACT)
Report()In this model, the Tomcat threads on AWS play the role of queueing servers.
PRETTY DAMN QUICK REPORT
==========================================
*** on Tue Nov 24 08:10:59 2020 ***
*** for AWS Tomcat Model ***
*** PDQ Version 7.0.0 Build 112420 ***
==========================================
==========================================
******** PDQ Model INPUTS ********
==========================================
Queueing Network Parameters
Node Sched Resource Workload Class Service time
---- ----- -------- -------- ----- ------------
MSC FCFS Threads Requests BATCH 0.444000
Network type: CLOSED
Workload streams: 1
Queueing nodes: 1
Workload Jobs R minimum
-------- ---- ----------
Requests 400.00 0.4440
==========================================
******** PDQ Model OUTPUTS ********
==========================================
Solution method: EXACT
******** SYSTEM Performance ********
Metric Value Unit
------ ------- ----
Workload: "Requests"
Mean concurrency 400.0000 Reqs
Mean throughput 675.6757 Reqs/Sec
Response time 0.5920 Sec
Stretch factor 1.3333
Bounds Analysis:
Max throughput 675.6757 Reqs/Sec
Min response 0.4440 Sec
Max demand 0.0015 Sec
Total demand 0.4440 Sec
Optimal jobs 300.0000 Jobs
******** RESOURCE Performance ********
Metric Resource Work Value Unit
------ -------- ---- ------- ----
Capacity Threads Requests 300 Servers
Throughput Threads Requests 675.6757 Reqs/Sec
In service Threads Requests 300.0000 Reqs
Utilization Threads Requests 100.0000 Percent
Queue length Threads Requests 400.0000 Reqs
Waiting line Threads Requests 100.0000 Reqs
Waiting time Threads Requests 0.1480 Sec
Residence time Threads Requests 0.5920 Sec