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Thread: [JAVASCRIPT] - Calculating Pi

  1. #1

    Thread Starter
    Addicted Member
    Join Date
    Apr 2006
    Posts
    155

    [JAVASCRIPT] - Calculating Pi

    I converted this from VB6 into Javascript:

    Code:
      function CalculatePi() // Calculates Pi by counting all the points around a circle making it easier and randomizing it.
    	 {
    	  var TOTAL_POINTS = new Number(1000000); //  points in pi (3.14159)
    		var x = new Number();
    		var y = new Number();
    		var points_in_circle = new Number();
    		var i = new Number();
    			  for (i;i<=TOTAL_POINTS;i++) // for i = 0 to 1000000 increasing by 1 increment every loop
    				 {
    				  x = Math.random() * 1; // random x between 0 and 1
    					y = Math.random() * 1; // random y between 0 and 1
    	          if (x * x + y * y < 1) // if both randomized to 0
    						 {
    						  points_in_circle = points_in_circle + 1; // increase points_in_circle
    						 }
    				 }
    				return 4 * points_in_circle / TOTAL_POINTS; // return answer to user
    	 }

  2. #2
    Member
    Join Date
    Jul 2019
    Location
    Ahmedabad
    Posts
    56

    Re: [JAVASCRIPT] - Calculating Pi

    Please try this code, To how to calculate PI using javascript.

    Code:
    <html>
      <head>
        <title>Pi</title>
        <script type="text/javascript">
          mess = "";
          Base = Math.pow(10, 11);
          cellSize = Math.floor(Math.log(Base) / Math.LN10);
          a = Number.MAX_VALUE;
          MaxDiv = Math.floor(Math.sqrt(a));
          function makeArray(n, aX, Integer) {
            var i = 0;
            for (i = 1; i < n; i++) aX[i] = null;
            aX[0] = Integer
          }
          function isEmpty(aX) {
            var empty = true
            for (i = 0; i < aX.length; i++) if (aX[i]) {
              empty = false;
              break
            }
            return empty
          }
          function Add(n, aX, aY) {
            carry = 0
            for (i = n - 1; i >= 0; i--) {
              aX[i] += Number(aY[i]) + Number(carry);
              if (aX[i] < Base) carry = 0;
              else {
                carry = 1;
                aX[i] = Number(aX[i]) - Number(Base)
              }
            }
          }
          function Sub(n, aX, aY) {
            for (i = n - 1; i >= 0; i--) {
              aX[i] -= aY[i];
              if (aX[i] < 0) {
                if (i > 0) {
                  aX[i] += Base;
                  aX[i - 1]--
                }
              }
            }
          }
          function Mul(n, aX, iMult) {
            carry = 0;
            for (i = n - 1; i >= 0; i--) {
              prod = (aX[i]) * iMult;
              prod += carry;
              if (prod >= Base) {
                carry = Math.floor(prod / Base);
                prod -= (carry * Base)
              } else carry = 0;
              aX[i] = prod
            }
          }
          function Div(n, aX, iDiv, aY) {
            carry = 0;
            for (i = 0; i < n; i++) {
              currVal = Number(aX[i]) + Number(carry * Base);
              theDiv = Math.floor(currVal / iDiv);
              carry = currVal - theDiv * iDiv;
              aY[i] = theDiv
            }
          }
          function arctan(iAng, n, aX) {
            iAng_squared = iAng * iAng;
            k = 3;
            sign = 0;
            makeArray(n, aX, 0);
            makeArray(n, aAngle, 1);
            Div(n, aAngle, iAng, aAngle);
            Add(n, aX, aAngle);
            while (!isEmpty(aAngle)) {
              Div(n, aAngle, iAng_squared, aAngle);
              Div(n, aAngle, k, aDivK);
              if (sign) Add(n, aX, aDivK);
              else Sub(n, aX, aDivK);
              k += 2;
              sign = 1 - sign
            }
            mess += "aArctan=" + aArctan + "<br>"
          }
          function calcPI(numDec) {
            var ans = "";
            t1 = new Date();
            numDec = Number(numDec) + 5;
            iAng = new Array(10);
            coeff = new Array(10);
            arrayLength = Math.ceil(1 + numDec / cellSize);
            aPI = new Array(arrayLength);
            aArctan = new Array(arrayLength);
            aAngle = new Array(arrayLength);
            aDivK = new Array(arrayLength);
            coeff[0] = 4;
            coeff[1] = -1;
            coeff[2] = 0;
            iAng[0] = 5;
            iAng[1] = 239;
            iAng[2] = 0;
            makeArray(arrayLength, aPI, 0);
            makeArray(arrayLength, aAngle, 0);
            makeArray(arrayLength, aDivK, 0);
            for (var i = 0; coeff[i] != 0; i++) {
              arctan(iAng[i], arrayLength, aArctan);
              Mul(arrayLength, aArctan, Math.abs(coeff[i]));
              if (coeff[i] > 0) Add(arrayLength, aPI, aArctan);
              else Sub(arrayLength, aPI, aArctan)
            }
            Mul(arrayLength, aPI, 4);
            sPI = "";
            tempPI = "";
            for (i = 0; i < aPI.length; i++) {
              aPI[i] = String(aPI[i]);
              if (aPI[i].length < cellSize && i != 0) {
                while (aPI[i].length < cellSize) aPI[i] = "0" + aPI[i]
              }
              tempPI += aPI[i]
            }
            for (i = 0; i <= numDec; i++) {
              if (i == 0) sPI += tempPI.charAt(i) + ".<br>";
              else {
                if (document.getElementById("cbCount").checked) addcount = " (" + (i) + ")";
                else addcount = "";
                if (document.getElementById("cbSpace").checked) thespace = " ";
                else thespace = "";
                if ((i) % 50 == 0 && i != 0) sPI += tempPI.charAt(i) + addcount + "<br>";
                else if (i % 5 == 0) sPI += tempPI.charAt(i) + thespace;
                else sPI += tempPI.charAt(i)
              }
            }
            ans += ("PI (" + numDec + ")=" + sPI + "<br>");
            ans += ("Win PI=<br>3.1415926535897932384626433832795<br>");
            t2 = new Date();
            timeTaken = (t2.getTime() - t1.getTime()) / 1000;
            ans += "It took: " + timeTaken + " seconds";
            var myDiv = document.getElementById("d1");
            myDiv.innerHTML = ans
          }
        </script>
      </head>
      <body>
        <h1>
          Pi Machin
        </h1>
        <form name="" id="" method="post" action="" enctype="text/plain" onsubmit="calcPI(this.t1.value);return false;">
          Number of Digits:<br>
          <input type="text" name="t1" id="t1" value="100" size="25" maxlength="25">
          <br>Add Count:
          <input type="checkbox" name="cbCount" id="cbCount" value="" checked="checked">
          <br>Add Spaces:
          <input type="checkbox" name="cbSpace" id="cbSpace" value="" checked="checked">
          <br>
          <input type="button" value="Calculate Pi" onclick="calcPI(this.form.t1.value)">
        </form>
        <div id="d1">0</div>
      </body>
    </html>
    
    I hope this code will be useful to you.
    Thank you.
    < advertising removed by moderator >

  3. #3
    PowerPoster
    Join Date
    Nov 2017
    Posts
    3,209

    Re: [JAVASCRIPT] - Calculating Pi

    Technically, the OP code is a Monte Carlo simulation that will generate a reasonable approximation of pi. But every time that code is ran, a slightly different result is likely to be returned.

    And I'm only adding this note because this thread was needlessly bumped already.

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