src/add/fsqrt.py

   1 def sqrt(num):
   2
   3     num = 6
   4
   5     res = 0
   6     bit = 1 << 14
   7
   8     while (bit > num):
   9         bit >>= 2
  10
  11     while (bit != 0):
  12         if (num >= res + bit):
  13             num -= res + bit
  14             res = (res >> 1) + bit
  15
  16         else:
  17             res >>= 1;
  18         bit >>= 2;
  19
  20     return res
  21
  22 """
  23 //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
  24 //
  25
  26 module testbench;
  27
  28 reg [15:0] sqr;
  29
  30 //Verilog function to find square root of a 32 bit number.
  31 //The output is 16 bit.
  32 function [15:0] sqrt;
  33     input [31:0] num;  //declare input
  34     //intermediate signals.
  35     reg [31:0] a;
  36     reg [15:0] q;
  37     reg [17:0] left,right,r;
  38     integer i;
  39 begin
  40     //initialize all the variables.
  41     a = num;
  42     q = 0;
  43     i = 0;
  44     left = 0;   //input to adder/sub
  45     right = 0;  //input to adder/sub
  46     r = 0;  //remainder
  47     //run the calculations for 16 iterations.
  48     for(i=0;i<16;i=i+1) begin
  49         right = {q,r[17],1'b1};
  50         left = {r[15:0],a[31:30]};
  51         a = {a[29:0],2'b00};    //left shift by 2 bits.
  52         if (r[17] == 1) //add if r is negative
  53             r = left + right;
  54         else    //subtract if r is positive
  55             r = left - right;
  56         q = {q[14:0],!r[17]};
  57     end
  58     sqrt = q;   //final assignment of output.
  59 end
  60 endfunction //end of Function
  61
  62
  63 c version (from paper linked from URL)
  64
  65 unsigned squart(D, r) /*Non-Restoring sqrt*/
  66     unsigned D; /*D:32-bit unsigned integer to be square rooted */
  67     int *r;
  68 {
  69     unsigned Q = 0; /*Q:16-bit unsigned integer (root)*/
  70     int R = 0; /*R:17-bit integer (remainder)*/
  71     int i;
  72     for (i = 15;i>=0;i--) /*for each root bit*/
  73     {
  74         if (R>=0)
  75         { /*new remainder:*/
  76             R = R<<2)|((D>>(i+i))&3);
  77             R = R-((Q<<2)|1); /*-Q01*/
  78         }
  79         else
  80         { /*new remainder:*/
  81             R = R<<2)|((D>>(i+i))&3);
  82             R = R+((Q<<2)|3); /*+Q11*/
  83         }
  84         if (R>=0) Q = Q<<1)|1; /*new Q:*/
  85         else Q = Q<<1)|0; /*new Q:*/
  86     }
  87
  88     /*remainder adjusting*/
  89     if (R<0) R = R+((Q<<1)|1);
  90     *r = R; /*return remainder*/
  91     return(Q); /*return root*/
  92 }
  93
  94 From wikipedia page:
  95
  96 short isqrt(short num) {
  97     short res = 0;
  98     short bit = 1 << 14; // The second-to-top bit is set: 1 << 30 for 32 bits
  99
 100     // "bit" starts at the highest power of four <= the argument.
 101     while (bit > num)
 102         bit >>= 2;
 103
 104     while (bit != 0) {
 105         if (num >= res + bit) {
 106             num -= res + bit;
 107             res = (res >> 1) + bit;
 108         }
 109         else
 110             res >>= 1;
 111         bit >>= 2;
 112     }
 113     return res;
 114 }
 115
 116 """