root/src/lua/test/bisect.lua

Revision 22d1941d0ca5ba7027cdfa51ce34bd1d8fb1931e, 0.6 kB (checked in by Theo Schlossnagle <jesus@omniti.com>, 6 years ago)

take the version out... it is what it is

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1 -- bisection method for solving non-linear equations
2
3 delta=1e-6      -- tolerance
4
5 function bisect(f,a,b,fa,fb)
6  local c=(a+b)/2
7  io.write(n," c=",c," a=",a," b=",b,"\n")
8  if c==a or c==b or math.abs(a-b)<delta then return c,b-a end
9  n=n+1
10  local fc=f(c)
11  if fa*fc<0 then return bisect(f,a,c,fa,fc) else return bisect(f,c,b,fc,fb) end
12 end
13
14 -- find root of f in the inverval [a,b]. needs f(a)*f(b)<0
15 function solve(f,a,b)
16  n=0
17  local z,e=bisect(f,a,b,f(a),f(b))
18  io.write(string.format("after %d steps, root is %.17g with error %.1e, f=%.1e\n",n,z,e,f(z)))
19 end
20
21 -- our function
22 function f(x)
23  return x*x*x-x-1
24 end
25
26 -- find zero in [1,2]
27 solve(f,1,2)
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