src/add/fsqrt.py

   1 def sqrt(num):
   2
   3    num ** (1/2)
   4
   5    return num
   6
   7
   8
   9
  10 """
  11 //This is the main code of integer sqrt function found here:http://verilogcodes.blogspot.com/2017/11/a-verilog-function-for-finding-square-root.html
  12 //
  13
  14 module testbench;
  15
  16 reg [15:0] sqr;
  17
  18 //Verilog function to find square root of a 32 bit number.
  19 //The output is 16 bit.
  20 function [15:0] sqrt;
  21     input [31:0] num;  //declare input
  22     //intermediate signals.
  23     reg [31:0] a;
  24     reg [15:0] q;
  25     reg [17:0] left,right,r;
  26     integer i;
  27 begin
  28     //initialize all the variables.
  29     a = num;
  30     q = 0;
  31     i = 0;
  32     left = 0;   //input to adder/sub
  33     right = 0;  //input to adder/sub
  34     r = 0;  //remainder
  35     //run the calculations for 16 iterations.
  36     for(i=0;i<16;i=i+1) begin
  37         right = {q,r[17],1'b1};
  38         left = {r[15:0],a[31:30]};
  39         a = {a[29:0],2'b00};    //left shift by 2 bits.
  40         if (r[17] == 1) //add if r is negative
  41             r = left + right;
  42         else    //subtract if r is positive
  43             r = left - right;
  44         q = {q[14:0],!r[17]};
  45     end
  46     sqrt = q;   //final assignment of output.
  47 end
  48 endfunction //end of Function
  49
  50
  51 c version (from paper linked from URL)
  52
  53 unsigned squart(D, r) /*Non-Restoring sqrt*/
  54     unsigned D; /*D:32-bit unsigned integer to be square rooted */
  55     int *r;
  56 {
  57     unsigned Q = 0; /*Q:16-bit unsigned integer (root)*/
  58     int R = 0; /*R:17-bit integer (remainder)*/
  59     int i;
  60     for (i = 15;i>=0;i--) /*for each root bit*/
  61     {
  62         if (R>=0)
  63         { /*new remainder:*/
  64             R = R<<2)|((D>>(i+i))&3);
  65             R = R-((Q<<2)|1); /*-Q01*/
  66         }
  67         else
  68         { /*new remainder:*/
  69             R = R<<2)|((D>>(i+i))&3);
  70             R = R+((Q<<2)|3); /*+Q11*/
  71         }
  72         if (R>=0) Q = Q<<1)|1; /*new Q:*/
  73         else Q = Q<<1)|0; /*new Q:*/
  74     }
  75
  76     /*remainder adjusting*/
  77     if (R<0) R = R+((Q<<1)|1);
  78     *r = R; /*return remainder*/
  79     return(Q); /*return root*/
  80 }
  81
  82 From wikipedia page:
  83
  84 short isqrt(short num) {
  85     short res = 0;
  86     short bit = 1 << 14; // The second-to-top bit is set: 1 << 30 for 32 bits
  87
  88     // "bit" starts at the highest power of four <= the argument.
  89     while (bit > num)
  90         bit >>= 2;
  91
  92     while (bit != 0) {
  93         if (num >= res + bit) {
  94             num -= res + bit;
  95             res = (res >> 1) + bit;
  96         }
  97         else
  98             res >>= 1;
  99         bit >>= 2;
 100     }
 101     return res;
 102 }
 103
 104 """