Good day! I have this code:
final class bench
{
protected static $start_time;
protected static $start_memory;
public static function start()
{
self::$start_time = microtime(true);
self::$start_memory = memory_get_usage(true)/1024;
}
public static function finish()
{
echo PHP_EOL.'+'.round(memory_get_usage(true)/1024 - self::$start_memory, 3).' Kb load';
echo PHP_EOL.'+'.round(microtime(true) - self::$start_time, 3).' Time.';
}
}
But when I wanna use this little code here:
bench::start();
$array = ['f', 'g', 'f', 'd', 'ff'];
foreach($array as $key=>$value)
{
echo $key.'f'.$value;
}
bench::finish();
I am getting bad results. It is saying me +0 Kb load +0 Time.
So I tried to use this example:
$start = memory_get_usage()/1024 . "\n";
for ($i = 1; $i <= 100; $i++) {
echo $i;
}
echo '<br/>+'.round(memory_get_usage()/1024 - $start, 3).' Kb load';
And then I got normal results. Why so? Probably, there is something better than the code above
Your code is working. The memory used is a few bytes ; since round the division to 3 digits, 0kb is displayed.
Related
I am trying to make a text game in PHP but i have problem since i am programing in php for few days. I need to call function attack (I need $_mainAttack since it is combination of $_baseAttack and special attack) from defend function so i can calculate the health loss I have placed -5 just to see if it is working..
Also in health i need attack to be able to lower hp so i could calculate the hp loss. My do while loop is wrong and i need help to make it functional. I want when health goes lower than 0 to exit the loop. When it exits the loop it will print game over. I am stuck in endless loop and i have no idea how to fix this.
This is index.php:
<?php
include 'Duel.php';
$duel = new Duel();
$duel->attack();
$duel->defend();
?>
This is my class duel:
<?php
class Duel{
public $_maxHealth = 20;
public $_currentHealth;
public $_baseAttack, $_specialAttack, $_mainAttack;
public $_specialChance, $deflectChance;
public $_defense;
function __construct()
{
echo 'begining of attack <br/>';
}
function attack()
{
$_specialChance = rand(0, 20);
$_specialAttack = 0;
if ($_specialChance < 10) {
$_specialAttack = 0;
} elseif ($_specialChance < 15) {
$_specialAttack = (int) rand(0, 5);
} elseif ($_specialChance <= 20) {
$_specialAttack = (int) rand(5, 10);
}
$_baseAttack = rand(1, 6);
$_mainAttack = $_baseAttack + $_specialAttack;
echo "Base attack is $_baseAttack: and special attack is : $_specialAttack attack is : $_mainAttack<br/>";
}
function defend()
{
$_maxHealth = 20;
do{
$deflectChance = rand(1, 10);
$deflect = 0;
if ($deflectChance < 5) {
$deflect = 0;
echo 'attack cannot be deflected';
}
elseif ($deflectChance > 5) {
$deflect = (int) rand(0, 3);
echo "attack is deflected for {$deflect} damage";
}
$_currentHealth = $_maxHealth + $deflect - 5;
echo "<br/>health is {$_currentHealth} <br/>";
}while($_currentHealth > 0);
if($_currentHealth > 0) echo "Game over";
}
} //end of class
You are always calculating $_currentHealth based on $_maxHealth, not the previous $_currentHealth.
Add before the loop:
$_currentHealth = $_maxHealth;
And change $_currentHealth = $_maxHealth + $deflect - 5; to:
$_currentHealth = $_currentHealth + $deflect - 5;
You can try returning the main attack variable from the attack function and simply call it on the defend function.
you are calculation $_mainAttack but doesn't subtract it from your health, therefore your player can't die and you end within an endless loop.
I am writing a program to sum the digits of a number , it is working fine for small numbers but for large no it is giving unexpected sum?
below is the program.
<?php
ini_set('display_errors', 1);
error_reporting(E_ALL);
class demo {
private $sum = 0;
private $num = 0;
private $rem = 0;
public function digit_sum($digit) {
//echo gettype($digit).'<br>';
try {
if (gettype($digit) == 'string') {
throw new Exception($digit . ' is not a valid number <br>');
} else {
$this->num = $digit;
while ($this->num > 0) {
$this->rem = $this->num % 10;
$this->sum = $this->sum + $this->rem;
$this->num = $this->num / 10;
}
return "Sum of no $digit is = " . $this->sum . '<br>';
}
} catch (Exception $e) {
echo $e->getMessage();
}
}
}
$sum = new demo();
echo $sum->digit_sum('sfsdfsdfds');
echo $sum->digit_sum(12345);
// outputs correct sum
echo $sum->digit_sum(3253435674);
//outputs incorrect sum
i see the above code results fine for integer no but not for double no'
please guide me what will be the perfect solution to this problem?
Do you know if you put a new echo $sum->digit_sum(32); The output will show you 62. Cause you create object once and call the same function multiple times. The object stores the sum for all the times.
Solution:
Just put an statement $this->sum = 0; before the while loop to clear the previous sum.
Online Example: https://3v4l.org/C7Yli.
Update: I tested the scripts in writephponline.com as per your comment and get the following result.
I want to create a function in which I put two values (value and its power - Example function: multiply(3, 3) result 27). I have tried so far but failed, I have searched using Google but I have been unable to find any result because I don't know the name of this function.
What I want exactly:
3,3 => 3 x 3 x 3 = 27
4,4 => 4 x 4 x 4 x 4 = 256
What I tried:
function multiply($value,$power){
for($x = 1; $x <= $value; $x++ ){
return $c = $value * $power;
}
}
echo multiply(3,3);
The answer has already been accepted, but I had to come here and say that all answers here use a bad algorithm. There are better ones. Including very simple ones, like exponentiation by squaring that reduces the complexity from O(power) to O(log(power)).
The idea is to square the base while dividing the exponent by 2. For example
3^8 = 9^4 = 81^2 = 6561
There is a special case when the exponent is odd. In this case, you must store a separate variable to represent this factor:
2^10 = 4^5 = 16^2 * 4 = 256 * 4 = 1024
PHP isn't one of my strong skills, but the final algorithm is as simple as:
function multiply($value, $power){
$free = 1;
while ($power > 1) {
if ($power % 2 == 1)
$free *= $value;
$value *= $value;
$power >>= 1; //integer divison by 2
}
return $value*$free;
}
echo multiply(3, 3) . "\n";
echo multiply(2, 10) . "\n";
echo multiply(3, 8) . "\n";
Oopsika, couldn't have asked a more obvious question. Use the built-in function named pow (as in a lot of languages)
echo pow(3, 3);
Edit
Let's create our own function.
function raiseToPower($base,$exponent)
{
// multiply the base to itself exponent number of times
$result=1;
for($i=1;$i<=$exponent;$i++)
{
$result = $result * $base;
}
return $result;
}
function exponent($value,$power)
{
$c=1;
for($x = 1; $x <= $power; $x++ )
{
$c = $value * $c;
}
return $c;
}
If you have PHP >= 5.6 you can use the ** operator
$a ** $b Exponentiation Result of raising $a to the $b'th power.
echo 2 ** 3;
If you have PHP < 5.6 you can use pow:
number pow ( number $base , number $exp )
echo pow(2, 3);
Your own function is:
function multiply($value, $power) {
$result = 1;
for($x = 1; $x <= $power; $x++){
$result *= $value;
}
return $result;
}
echo multiply(3,3);
Read more at:
http://php.net/manual/en/language.operators.arithmetic.php
http://php.net/manual/en/function.pow.php
Just try to run this code I hope your problem will be solved.
If you defining any function then you have to call it return value.
<?php
function multiply($value,$exp)
{ $temp=1;
if($exp==0)
return $temp;
else
{
for($i=1;$i<=$exp;$i++)
$temp=$temp*$value;
return $temp;
}
}
echo multiply(5,6);
?>
echo "Enter number (will be mutiplied):".PHP_EOL;
$value = (int) readline("> ");
echo "Enter number for multiplier:".PHP_EOL;
$multiplier = (int) readline("> ");
function power(int $i, int $n):int {
$result =1;
for ($int = 1; $int < $n; $int++){
$result *= $i;
}
return $result;
}
echo power($value,$multiplier);
I've created a memoized function of the recursive version of fibonacci.
I use this as an example for other kinds of functions that would use memoization.
My implementation is bad since if I include it in a library, that means that the global variable is still seen..
This is the original recursive fibonacci function:
function fibonacci($n) {
if($n > 1) {
return fibonacci($n-1) + fibonacci($n-2);
}
return $n;
}
and I modified it to a memoized version:
$memo = array();
function fibonacciMemo($n) {
global $memo;
if(array_key_exists($n, $memo)) {
return $memo[$n];
}
else {
if($n > 1) {
$result = fibonacciMemo($n-1) + fibonacciMemo($n-2);
$memo[$n] = $result;
return $result;
}
return $n;
}
}
I purposely didn't use the iterative method in implementing fibonacci.
Is there any better ways to memoize fibonacci function in php? Can you suggest me better improvements? I've seen func_get_args() and call_user_func_array as another way but I can't seem to know what is better?
So my main question is: How can I memoize fibonacci function in php properly? or What is the best way in memoizing fibonacci function in php?
Well, Edd Mann shows an excellent way to implement a memoize function in php in His post
Here is the example code (actually taken from Edd Mann's post):
$memoize = function($func)
{
return function() use ($func)
{
static $cache = [];
$args = func_get_args();
$key = md5(serialize($args));
if ( ! isset($cache[$key])) {
$cache[$key] = call_user_func_array($func, $args);
}
return $cache[$key];
};
};
$fibonacci = $memoize(function($n) use (&$fibonacci)
{
return ($n < 2) ? $n : $fibonacci($n - 1) + $fibonacci($n - 2);
});
Notice that the global definition it's replaced thanks to function clousure and PHP's first-class function support.
Other solution:
You can create a class containing as static members: fibonnacciMemo and $memo. Notice that you don't longer have to use $memo as a global variable, so it won't give any conflict with other namespaces.
Here is the example:
class Fib{
//$memo and fibonacciMemo are static members
static $memo = array();
static function fibonacciMemo($n) {
if(array_key_exists($n, static::$memo)) {
return static::$memo[$n];
}
else {
if($n > 1) {
$result = static::fibonacciMemo($n-1) + static::fibonacciMemo($n-2);
static::$memo[$n] = $result;
return $result;
}
return $n;
}
}
}
//Using the same method by Edd Mann to benchmark
//the results
$start = microtime(true);
Fib::fibonacciMemo(10);
echo sprintf("%f\n", microtime(true) - $start);
//outputs 0.000249
$start = microtime(true);
Fib::fibonacciMemo(10);
echo sprintf("%f\n", microtime(true) - $start);
//outputs 0.000016 (now with memoized fibonacci)
//Cleaning $memo
Fib::$memo = array();
$start = microtime(true);
Fib::fibonacciMemo(10);
echo sprintf("%f\n", microtime(true) - $start);
//outputs 0.000203 (after 'cleaning' $memo)
Using this, you avoid the use of global and also the problem of cleaning the cache. Althought, $memo is not thread save and the keys stored are no hashed values.
Anyways, you can use all the php memoize utilites such as memoize-php
i think... this should to to memoize a fibonacci:
function fib($n, &$computed = array(0,1)) {
if (!array_key_exists($n,$computed)) {
$computed[$n] = fib($n-1, $computed) + fib($n-2, $computed);
}
return $computed[$n];
}
some test
$arr = array(0,1);
$start = microtime(true);
fib(10,$arr);
echo sprintf("%f\n", microtime(true) - $start);
//0.000068
$start = microtime(true);
fib(10,$arr);
echo sprintf("%f\n", microtime(true) - $start);
//0.000005
//Cleaning $arr
$arr = array(0,1);
$start = microtime(true);
fib(10,$arr);
echo sprintf("%f\n", microtime(true) - $start);
//0.000039
Another solution:
function fib($n, &$memo = []) {
if (array_key_exists($n,$memo)) {
return $memo[$n];
}
if ($n <=2 ){
return 1;
}
$memo[$n] = fib($n-1, $memo) + fib($n-2, $memo);
return $memo[$n];
}
Performance:
$start = microtime(true);
fib(100);
echo sprintf("%f\n", microtime(true) - $start);
// 0.000041
This's an implementation of memoize a fibonacci:
function fib(int $n, array &$memo = [0,1,1]) : float {
return $memo[$n] ?? $memo[$n] = fib($n-1, $memo) + fib($n-2, $memo);
}
Call
echo fib(20); // 6765
function fibMemo($n)
{
static $cache = [];
//print_r($cache);
if (!empty($cache[$n])) {
return $cache[$n];
} else {
if ($n < 2) {
return $n;
} else {
$p = fibMemo($n - 1) + fibMemo($n - 2);
$cache[$n] = $p;
return $p;
}
}
}
echo fibMemo(250);
I have a doubt in memory allocation with a php 5.3 script.
Imagine you have 2 static classes (MyData and Test) like these:
class MyData {
private static $data = null;
public static function getData() {
if(self::$data == null)
self::$data = array(1,2,3,4,5,);
return self::$data;
}
}
class Test {
private static $test_data = null;
public static function getTestData1() {
if(self::$test_data==null) {
self::$test_data = MyData::getData();
self::$test_data[] = 6;
}
return self::$test_data;
}
public static function getTestData2() {
$test = MyData::getData();
$test[] = 6;
return $test;
}
}
And a simple test.php script:
for($i = 0; $i < 200000; $i++) {
echo "Pre-data1 Test:\n\t" . memory_get_usage(true) . "\n";
Test::getTestData1();
echo "Post-data1 Test:\n\t" . memory_get_usage(true) . "\n";
}
for($i = 0; $i < 200000; $i++) {
echo "Pre-data2 Test:\n\t" . memory_get_usage(true) . "\n";
Test::getTestData2();
echo "Post-data2 Test:\n\t" . memory_get_usage(true) . "\n";
}
I might suppose that the call to Test::getTestData1() will alloc memory for 2 static variables, while Test::getTestData2() will destroy $test (the copy of the static variable) on function return, so the second call is less "memory expensive".
But if I run the test.php script, memory_get_usage will show the same values for Test::getTestData1() and Test::getTestData2()
Why?
You are testing memory usage in the wrong way.
use memory_get_usage(false); to get the memory that is actually used by the script.
memory_get_usage(true); simply returns the memory allocated by System and this will always be the same for small scripts.