attempting to write a fixed point sqrt function
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Hi everybody;
I am trying to write a function to cubicly converge on a solution to a square root in fixed point. I am getting bad overflow and when I try to bitshift to eliminate it my solutions reduce to zero. My code is included below. Please help.
function [iterSqrt] = iterFixedPointSqrtCC (val)
numIter = 20;
x = zeros(numIter,1);
x(1) = 1*2^24;
botlim = 1;
if val < botlim
x(numIter) = 0;
else
for n = (2:1:numIter)
x(n-1) = int32(x(n-1));
xnMinusOneSq = bitshift(bitshift(x(n-1),-8)*bitshift(x(n-1),-8),-8);
topLineBkts = xnMinusOneSq+3*val;
botLine = 3*xnMinusOneSq+val;
topLine = bitshift(x(n-1),-12)*bitshift(topLineBkts,-12);
x(n) = int32(bitshift(bitshift(uint32(topLine),6)/bitshift(uint32(botLine),-6),12));
end
end
iterSqrt = x(numIter);
I am using a for loop as while loops do tend to be problematic when going for an embedded target. the value to be rooted comes in scaled by 2^24. I am attempting to implement method 3 from http://chenfuture.wordpress.com/2008/01/03/simple-ways-to-compute-square-root/.
Any suggestions are most welcome.
Thanks
Amardeep
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