Create numbers within an array that add up to a set amount

Question

I\'m fairly new to PHP - programming in general. So basically what I need to accomplish is, create an array of x amount of numbers (created randomly) whose value add up

Answer 1

sorry i missed 'no duplicates' too
-so need to tack on a 'deduplicator' ...i put it in the other question

To generate a series of random numbers with a fixed sum:

• make a series of random numbers (of largest practical magnitude to hide granularity...)
• calculate their sum
• multiply each in series by desiredsum/sum

(basicaly to scale a random series to its new size)

Then there is rounding error to adjust for:

• recalculate sum and its difference from desired sum
• add the sumdiff to a random element in series if it doesnt result in a negative, if it does loop to another random element until fine.
• to be ultratight instead add or subtract 1 bit to random elements until sumdiff=0

Some non-randomness resulting from doing it like this is if the magnitude of the source randoms is too small causing granularity in the result.

I dont have php, but here's a shot -

$n = ;              //size of array
$targsum = ;        //target sum
$ceiling = 0x3fff;  //biggish number for rands
$sizedrands = array();

$firstsum=0;
$finsum=0;

//make rands, sum size
for( $count=$n; $count>0; $count--)
{ $arand=rand( 0, $ceiling );
  $sizedrands($count)=$arand;
  $firstsum+=$arand; }

//resize, sum resize
for( $count=$n; $count>0; $count--)
{ $sizedrands($count)=($sizedrands($count)*$targsum)/$firstsum;
  $finsum+=$sizedrands($count);
  }

//redistribute parts of rounding error randomly until done
$roundup=$targsum-$finsum;

$rounder=1; if($roundup<0){ $rounder=-1; }

while( $roundup!=0 )
{ $arand=rand( 0, $n );
  if( ($rounder+$sizedrands($arand) ) > 0 )
  { $sizedrands($arand)+=$rounder; 
    $roundup-=$rounder; }
  }