Ventana software support forum

Hi there,

I've been pondering over a problem for ages now and can't seem to get round it. Hopefully someone will be able to help me?

I have an input that is a set of pulses randomly distributed over one month. At this point I do not know the width ie time the pulse is to run for so I have set it to 1.

I need to increase the width of the pulse as it passes through processes which have a time associated with them.

An additional problem I am having is that I have three separate strands of these pulses and where there is a pulse at the same time, I need to increase the height of the pulse.

To summarise:

immediate pulse: 10010010
urgent pulse: 01011100
routine pulse: 00001111

I would like this to add the pulses to show: 11022221

This would also need to show the time delays of each pulse.
So, immediate once through all the processes should be a width of 24 hrs, urgent 168 hrs and routine 336 hrs. Note these times are all the delays added together, but I would need to show the status after each delay.

Any help would be much appreciated.

Gem

I assume your pulses are intended as inputs - you may make more progress thinking about the nature of the process rather than a mathematical abstraction of it. I will assume the pulses are new jobs to do and eacdh job has a time it takes to do it then

immediate jobs = INTEG(immediate starts-immediate finishes,0)
immediate finishes = DELAY FIXED(immediate starts,immediate job time)

similarly for urgent and routime. Total jobs is then just immediate + urgent + routine.

Hi Bob,

Thanks for your reply. Unfortunately, there is a bit more to each job than just starting and finishing. The model needs to send pulses down different routes to get to the finish point, some are redesignated, rejected etc. I need to show an accumulation of jobs after each process - the aim is to show the effect of an increase/decrease in throughput and/or time delays.

Any ideas on how I can do it with the pulses?

Thanks,

Gemma

I can't make any sense of what problem you are trying to work. I can understand redesignating material flows and rejecting work in progress but a pulse is an abstract mathematical concept and I have never seen one in real life. Reading between the lines I think you need to map all the different paths a piece of work can take. You can then either take an aggregate view of the processes (as for example with project models and quality leading to undiscovered rework) or you can try to break the universe up into objects that will follow different paths.

You can either implement each object as a subscript, use fractional objects, or perhaps reconceptualize the model as a discrete event process model - in which case Vensim might not be the best choice for executing on this.