Performance/memory problems with arrays?

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: 7bit

I am working on some financial calculators and although I succeeded to  
created the required formulas I am not sure about the following.To give an  
example: when somebody puts a capital on the bank with a yearly interest of  
x %  , the final capital after, say, 30 years can easily be calculated.  
Since I want to be able to show the capital created after every year I  
prefer to do it with a loop, something like
for($x= 1; $x < 30; $x++){
    $capital = $capital*(1 + $interest /100)
} .
Another reason for such a loop is that the visitor could tell that he want  
to withdraw some capital in the so-manieth year
Now let's say the visitor of the page can do a "quick scan" (just showing  
the final amount)  and request a table with all the yearly amounts  
afterwards. In this case I will either have to store all the yearly capital  
values into a an array and register that array to a session, or I will need  
to do the whole loop again but this time something like
    $capital = $capital*(1+ $interest/100);
    echo "<tr><td>$capital</td></tr>";
Although the formulas I "translated" from several excel sheets work fine, I  
would like to know if storing such arrays could have negative consequences  
for performance or memory on the server
Alternative suggestions, of course are also welcome. I tried to find similar  
scripts on Google but I wasn't very successfull, probably because I am not  
very familiar with the English financial terms

Thanks for any help.


Re: Performance/memory problems with arrays?

Martien van Wanrooij wrote:
Quoted text here. Click to load it


Programming is all about tradeoffs.  Often time the tradeoff is between  
memory and cpu utilization.

Would storing arrays have negative consequences?  Sure.  But so would  
calculating the figures every time.

Which is better?  It's impossible to tell.  It all depends on your  
server, your users (both number and frequency) and probably a dozen  
other things.

You need to figure out how much data you're talking about and how often  
it's being requested.  That will help you determine which is the better  
way to go.

Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.

Re: Performance/memory problems with arrays?

Quoted text here. Click to load it
Thanks Jerry, the problem is that I am not very "handy"  at estimating such  
performance issues, maybe it is just a matter of experience. Not that I am  
extremely  worried that my mortgage calculation will be visited at the same  
time by so many visitors that it would make crash my hosting provider's  
server but I want to take in mind such considerations from the very  
beginning. Anyway your reaction makes me think that I shouldn't be too  
worried about the script I am writing, thanks agein :)

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