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CoffeeScript Javascript Fast Fibonacci
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Author: Jason Giedymin <jasong _a_t_ apache -dot- org>
http://www.jasongiedymin.com
https://github.com/JasonGiedymin
This CoffeeScript Javascript Fast Fibonacci code is
based on the python code from Robin Houston's blog.
See below links.
A few things I want to introduce in time are implementions of
Newtonian, Burnikel / Ziegler, and Binet's algorithms on top
of a Big Number framework.
Todo:
- https://github.com/substack/node-bigint
- BZ and Newton mods.
- Timing
Cool Links:
http://bosker.wordpress.com/2011/04/29/the-worst-algorithm-in-the-world/
http://www.math.rutgers.edu/~erowland/fibonacci.html
http://jsfromhell.com/classes/bignumber
http://www.math.rutgers.edu/~erowland/fibonacci.html
http://bigintegers.blogspot.com/2010/11/square-division-power-square-root.html
http://bugs.python.org/issue3451
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MAXIMUM_JS_FIB_N = 1476
fib_bits = (n) ->
#Represent an integer as an array of binary digits.
bits = []
while n > 0
[n, bit] = divmodBasic(n, 2)
bits.push(bit)
#bits.reverse()
return bits.reverse()
fibFast = (n) ->
#Fast Fibonacci
if n < 0
console.log "Choose an number >= 0"
return
[a, b, c] = [1, 0, 1]
for bit in fib_bits(n)
if bit
[a, b] = [(a+c)*b, b*b + c*c]
else
[a, b] = [a*a + b*b, (a+c)*b]
c = a + b
return b
divmodBasic = (x, y) ->
###
Absolutely nothing special here. Maybe later versions will be Newtonian or
Burnikel / Ziegler _if_ possible...
###
return [(q = Math.floor(x/y)), (r = if x < y then x else x % y)]
start = (new Date).getTime();
calc_value = fibFast(MAXIMUM_JS_FIB_N)
diff = (new Date).getTime() - start;
console.log("[#{calc_value}] took #{diff} ms.")
Owner

JasonGiedymin commented Oct 12, 2011

Previous versions of this app had weird formatting. Blame Cygwin, fixed on my Mac. ;-)

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