[Space] DIV/0 error in starsystem generation sequence
 

In the the starsystem generation sequence in GURPS Space it is possible for a star system to have an age of 0. Since the unit of measure is billions of years, and the table entries go to one decimal place (with a '5', sometimes, in the second decimal place), this is fair enough. Age = 0 represents systems younger than about 250 million years.

However, in the rules for generating the level of volcanic activity (Step 31, on p.119) you divide surface gravity by age. This can produce a divide-by-zero error.

Re: [Space] DIV/0 error in starsystem generation sequence
 

Perhaps substituting 0.25 (or 0.125, or a random value between 0 and 0.25) for 0 would solve your problem?

Re: [Space] DIV/0 error in starsystem generation sequence
 

Mathematically that's an error, yes. In actual fact, though, those star systems don't have an age of zero; they have an age that rounds down to zero when you divide by 10^8—that is, anything less than 50 million years. The rounding produces problems for the specific case of figuring volcanic activity.

You could assume an arbitrary age of, say, 50 million years (0.05 billion). But I would suggest an even simpler approach. If the modified roll for volcanic activity is 71 or higher, you get extreme vulcanism. Infinity is greater than 71. So just treat it as "increases without limit" and as automatically greater than 71—that is, every world in such a system has extreme vulcanism. Save the dice roll entirely.

Bill Stoddard

Re: [Space] DIV/0 error in starsystem generation sequence
 

Is this a problem with a spreadsheet? I don't find it to be a problem in in principle because an age 0 star would presumably not have any planets anyway, just coagulating clouds of dust.

Re: [Space] DIV/0 error in starsystem generation sequence
 

Not any more. I put in yet another exception trap to handle it. (Exception handling in spreadsheet programming is a lot of fun.)

Re: [Space] DIV/0 error in starsystem generation sequence
 

Just so. There is no fundamental problem that is not easily sidestepped with a bit of understanding and circumspection. It is only when you attempt to apply the rules in a mechanical way that you encounter the problem. As for instance when you are coding the algorithm for a computer to execute.

Indeed. Programming conventionally that means that before you execute the division statement you test the exception and force a result of at least 71. Programming on a spreadsheet is equivalent, but done slightly differently.

Exception testing before any division is routine for professional programmers. But I didn't think that it was a bad idea not to give the many amateurs who are having a go at this project a 'heads up' about a potential run-time error.

Re: [Space] DIV/0 error in starsystem generation sequence
 

As whswhs emphasised, they aren't really age zero. Age has been rounded to the nearest whole multiple of 0.05 billion years. 'Age 0' represents anything up to 25 million years.

Re: [Space] DIV/0 error in starsystem generation sequence
 

If your sheets are like mine, they'll end up full of cells that are cluttered with nested IF(.....) statements, none of which make any sense the next morning.

Re: [Space] DIV/0 error in starsystem generation sequence
 

It goes in waves. Sometimes there are carefully-named columns full of condition flags.

Re: [Space] DIV/0 error in starsystem generation sequence
 

Didn't think they were, but I'd still class them as "too young to have planets".

Re: [Space] DIV/0 error in starsystem generation sequence
 

At 25 million years? The planets might be rather hot, but I think they'd be there.

Re: [Space] DIV/0 error in starsystem generation sequence
 

Sounds more like orbiting goo than planets, but close enough, eh?