<< Chapter < Page Chapter >> Page >

Function calls are another standard kind of control flow. Surprisingly, Promela does not have function calls ! Every proctype instance is a separate process. Though if you really want, you could simulate a function call by creating a new process dynamically , and blocking until that process returns.


So far, we have determined the possible behaviors of a program simply by running the program abunch of times. For small programs, we can be very careful and make sure we exhibit all the possible traces, but the state spacesoon becomes unwieldy.

The real power of SPIN is as a tool for verification, our original goal.SPIN will search the entire state space for us , looking for (reachable) states which fail to have desired properties.


The first verification technique we'll examine are assertion s, common to many programming languages. In Promela, the statement assert( condition ); evaluates the condition. If the result is true, execution continues as usual. Otherwise, the entire programis aborted and an error message is printed.

When simulating a single run of the program, SPIN automatically checks these run-time assertions;this is the usage that most programmers should be familiar with from traditional programming languages.But additionally, we'll see that SPIN, in the course of searching the entire state space,verifies whether an assertion can ever fail! (Though of course it can only search finite, feasible state spaces;happily,feasiblecan often include hundreds of millions of states.)

Consider our last race condition example . One of our original nave expectations was that, within each process,the value of z at the end of the process is exactly one more than at the beginning.The previous examples have shown that to be wrong, but we had to run the program until we encountered a run when it failed.Here, the assert statement puts that expectation explicitly into the program, for SPIN to check. 1 #define NUM_PROCS 3 23 show int z = 0; 45 active[NUM_PROCS] proctype increment()6 { 7 show int new_z;8 9 /* A saved copy of the old z, for the assertion. */10 show int old_z; 1112 old_z = z; 13 new_z = old_z + 1;14 z = new_z; 1516 assert(z == old_z+1); 17 }

It is often the case, as it is here, that to state the desired condition we need to add an extra variablehere, old_z . As always, it is important that when introducing such code fortesting that you don't substantially change the code to be tested, lest you inadvertently introduce new bugs!

Run this code several times, and observe when the assertion fails.This text indicates which assertion failed, and the line will be highlighted in the code window. To see which process' copy of increment failed and why, you have to look more closely at the steps shown. spin: line 16 "pan_in", Error: assertion violated spin: text of failed assertion: assert((z==(old_z+1)))

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Model checking concurrent programs. OpenStax CNX. Oct 27, 2005 Download for free at http://cnx.org/content/col10294/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Model checking concurrent programs' conversation and receive update notifications?