Comment simuler rouler les dés plusieurs fois en utilisant PHP

Question

Je veux simuler rouler deux nombres à six faces des dés X de fois en utilisant PHP pour voir à quelle fréquence chaque combinaison possible se fait (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ou 12). Quel serait un bon point de départ?

Answer 1

Voici un script PHP complet qui simule deux dés autant de fois que vous le souhaitez, puis afficher les totaux de fonctionnement des résultats de chaque rouleau:

<?php 

/** 
* If your machine is low on memory, try uncommenting the following line: 
*/ 
//ini_set('memory_limit', '512M'); 

/** 
* If you still don't have enough memory, reduce the value of $number_of_rolls 
* Note: with memory_limit at 512M, the max number of times I can roll at a time 
* is about 325000 
*/ 
$number_of_rolls = 20000; 
print dice_roll_output($number_of_rolls); 

/** 
* Array of 6 sides in a single die 
*/ 
function die_render() { 
    $die = array(1 => 1, 2, 3, 4, 5, 6); 
    return $die; 
} 

/** 
* Roll a single die 
*/ 
function die_roll($die_sides) { 
    // First function (less random) 
    //$number_rolled = array_rand($die_sides); 

    // Second function (more random) 
    $number_rolled = mt_rand(1, count($die_sides)); 

    return $number_rolled; 
} 

/** 
* Roll both dice 
*/ 
function dice_roll() { 
    // Create the first die 
    $die1 = die_render(); 
    // Create the second die 
    $die2 = die_render(); 
    // Roll the first die 
    $die_roll_1 = die_roll($die1); 
    // Roll the second die 
    $die_roll_2 = die_roll($die2); 
    // Add the two rolls up to get the total 
    $total = $die_roll_1 + $die_roll_2; 
    // Return the first die, second die, and the total of the two 
    return array($die_roll_1, $die_roll_2, $total); 
} 

/** 
* Much of this function is not necessary unless the 
* area toward the bottom is un-commented out. 
*/ 
function dice_roll_output($numrolls) { 
    $numrolls = (int) $numrolls; 
    // Abort if $numrolls is less than 1 
    if ($numrolls < 1) { 
    return 'Number of rolls must be greater than zero'; 
    } 
    $rolled_arr = array(); 
    $die1 = array(); 
    $die2 = array(); 
    $dice_sum = array(); 
    for ($i = 0; $i < $numrolls; $i++) { 
    $dice_roll[$i] = dice_roll(); 
    $die1[$i] = $dice_roll[$i][0]; 
    $die2[$i] = $dice_roll[$i][1]; 
    $dice_sum[$i] = $dice_roll[$i][2]; 
    $rolled_arr[$i] = array($die1[$i], $die2[$i], $dice_sum[$i]); 
    } 
    // How many times each total (somewhere between 2 and 12) was rolled 
    $frequencies = array_count_values($dice_sum); 
    // Sort the displayed output from high to low 
    arsort($frequencies); 
    // For later use with calculating percentages 
    $rolled_tot = array_sum($frequencies); 
    // Begin actual display -- line 1 
    $out = "<pre><b>Rolled\t\tFrequency\tPercent</b>\n"; 
    // Double-checking to make sure all percentages add up to 100% 
    $freqency_total = 0; 
    foreach ($frequencies as $dice_roll => $frequency) { 
    // Don't round the numbers using number_format until after they've been used 
    // for double-checking 
    $percent_raw = ($frequency/$rolled_tot) * 100; 
    // Add to the running total of the double-checked percentage 
    $freqency_total += $percent_raw; 
    // Now we can round the numbers up to two decimal places 
    $percent_display = number_format($percent_raw, 2); 
    // More display -- should be 11 lines maximum (lines 2 through 12) 
    $out .= "{$dice_roll}\t\t{$frequency}\t\t{$percent_display}\n"; 
    } 
    // Format the running total of the double-checked percentage (optional) 
    $freqency_total = number_format($freqency_total, 2); 
    // Aesthetic purposes only 
    $out .= "\t\t\t\t-----\n"; 
    // Line 13 of the display 
    $out .= "\t\t\t\t{$freqency_total}%\n"; 

    // The following is the above-referenced "area toward the bottom" 
    // NB: displaying this part could cause a LOT of output to be displayed 

    /* 
    if (!empty($rolled_arr)) { 
    // Uncomment the next line if you want to sort the output 
    //array_multisort($dice_sum, SORT_DESC, $rolled_arr); 

    // Aesthetic purposes only 
    $out .= "---------------------------------------\n"; 
    // Line 14 of the display 
    $out .= "<b>Die #1\t\tDie #2\t\tTotal</b>\n"; 
    foreach ($rolled_arr as $key => $arr) { 
     // Lines 15 and up of the display -- quantity determined by $numrolls 
     $out .= "{$arr[0]}\t\t{$arr[1]}\t\t{$arr[2]}\n"; 
    } 
    } 
    */ 
    // End actual display 
    $out .= "</pre>"; 
    return $out; 
} 

Answer 2

Voici un petit script avec des commentaires simples sur ce qui fait quoi.

<?php 

// this will be our final result 
$combinations = array(); 

// for as many times as we want to run the experiment (1000 here) 
for ($i = 0; $i < 1000; $i++) { 
    // mt_rand returns random whole number in the specified range 
    $die1roll = mt_rand(1, 6); 
    $die2roll = mt_rand(1, 6); 

    // add the sum of two dice 
    $sum = $die1roll + $die2roll; 

    // if this sum hasn't happened yet, mark it so - it's happened zero times 
    if (!isset($combinations[$sum])) $combinations[$sum] = 0; 

    // increase number of times this sum has happened 
    $combinations[$sum] += 1; 
} 

// order the results array by keys (sums) ascending 
ksort($combinations); 

// print it out 
print_r($combinations);