tests/fail/demo_bisect.lua@f9bb0e212d28 (annotated)
tests/fail/demo_bisect.lua
Wed, 24 Nov 2010 02:52:37 +0000
- author
- Matthew Wild <mwild1@gmail.com>
- date
- Wed, 24 Nov 2010 02:52:37 +0000
- changeset 138
- f9bb0e212d28
- parent 57
- 3e148db7f933
- permissions
- -rw-r--r--
Replace error reporting code with calls to LVM.traceback()
| 57 | 1 | -- bisect.lua |
| 2 | -- bisection method for solving non-linear equations | |
| 3 | ||
| 4 | delta=1e-6 -- tolerance | |
| 5 | ||
| 6 | function bisect(f,a,b,fa,fb) | |
| 7 | local c=(a+b)/2 | |
| 8 | io.write(n," c=",c," a=",a," b=",b,"\n") | |
| 9 | if c==a or c==b or math.abs(a-b)<delta then return c,b-a end | |
| 10 | n=n+1 | |
| 11 | local fc=f(c) | |
| 12 | if fa*fc<0 then return bisect(f,a,c,fa,fc) else return bisect(f,c,b,fc,fb) end | |
| 13 | end | |
| 14 | ||
| 15 | -- find root of f in the inverval [a,b]. needs f(a)*f(b)<0 | |
| 16 | function solve(f,a,b) | |
| 17 | n=0 | |
| 18 | local z,e=bisect(f,a,b,f(a),f(b)) | |
| 19 | io.write(string.format("after %d steps, root is %.17g with error %.1e, f=%.1e\n",n,z,e,f(z))) | |
| 20 | end | |
| 21 | ||
| 22 | -- our function | |
| 23 | function f(x) | |
| 24 | return x*x*x-x-1 | |
| 25 | end | |
| 26 | ||
| 27 | -- find zero in [1,2] | |
| 28 | solve(f,1,2) | |
| 29 |
