Linear Decrease Algorithm

Maybe this:

function x($a)
{
	return rand(0, $a-1);
}
echo x(25);

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Thanks for the response, but this is not what i'm after.

I need it so that the return value is constant, not randomized.

Note: i should have named the topic "nonlinear decrease algorithm", as i wish to cause the decrease to become more significant as the provided value increases.

Nerotech: What rules would you apply to determine how much smaller the return value should be?

Strange solution:

<?PHP
function x($a)
{
	$b = substr(abs(crc32($a)), 0, 1);
	return ($a-$b > 0 ? $a-$b : 1);
}
echo x(46);
?>

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Well initially I would prefer the returned value to be ~10% less of the provided value, as the value increments I would like the percentage to decrease more rapidly and Eventually the returned value would be 99.9% less than the original.

The point at which 99.9% less should be >=10,000

To summarize:

Start value >=0 && <=25 (-10%)
End value >=10,000 (-99.9%)

Percentage removed per increment will initially start slow, but will become more apparent at ~1,000.

What kind of calculations are you doing? Something like showing an animation in x seconds with a varying start/end or something?

function non_linear_decrease($input)
{
  if ($input < 0 ) { return 0; }
  
  $input_temp = $input;
  $multiplier = 1;
  while (($input_temp / 10) )  > 10) {
    $multiplier = $multiplier * .9;
    $input_temp = $input_temp / 10; 
  }
 
  return $input * $multiplier;
}

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Still not sure I understand the function.  Could you sketch a curve that would show what you're seeking?
nerotech-function.gif

Yes Ray, thats exactly what i'm after.

shinji,
how do the results of the function i supplied compare to what you want?

Virmaior: its not what i'm after.

Test values:
25-100 (0% difference)
101 (9.1% difference)
10,000 (19% difference)

Shinji: I have to leave and can't work on this, but it looks like you need a parabola with a horizontal axis.

http://www.intmath.com/Plane-analytic-geometry/4_Parabola.php

Good luck! ~Ray

K‰“Uc_hFg‚mSŒoiFgYK

function nonlinear_decrease($input)
{
   if (($input > 25) and ($input < 100)) { return $input; }
  return $input * (1 - log($input,1.62));
}

that gets the values you are looking for
(19% for 10000) and (9% for 100)

or rather return $input * (1 - ( log($input,1.62) / 100));

kore de ha nihon no kanji wo kaite dekimasen. shikashi, saisho no hoshikatta no kotae to ima no sagashiteru no kotae ha chigaimashita no?

Sorry Virmaior, i should have been less ambiguous with my response (and original question).
Those were the test values & results i used on the function that you provided earlier.

The values i need are:

Start value >=0 && <=25 (-10%)
End value >=10,000 (-99.9%)

with nonlinear increase (see the graph Ray posted).

Ray is correct in pointing out that I require a parabolic function (Quadrant I).

Great, thanks alot Ray, works perfect! :)

Glad to help!  BTW, that algorithm (when unconstrained) is the central element of single-server queueing theory.  Response Time = Service Time divided by (1 - Percent Busy).  I have used it for years to predict computer performance under increasing loads.  Nice to see it serves your needs, too.