Computing polynomials with few multiplications
description
Transcript of Computing polynomials with few multiplications
COMPUTING POLYNOMIALS WITH FEW MULTIPLICATIONS
973311 張弘暐 973320 江宗翰指導教授 :張經略
作者 : Shachar Lovett
ECCC(Electronic Colloquium on Computational Complexity)
目的 改進計算多項式的時間複雜度 將 upper bound 接近 lower bound
Lower bound :
原先 Upper bound :
新 Upper bound :
n 項多項式 degree ≤ d
ටቀn+ dn ቁ
○(1nቀn+ dn ቁ)
ටቀn+ dn ቁ. (nd)o(1)
例 : n = 3 , d = 5
n 項多項式 degree ≤ d
x1
x2
x3
2 2 1 x1
x2
x3
2 1 2
x1
x2
x3
3 1 0
MONOTONE( 單調函數 ) x ≤ y if and only if f (x) ≤ f (y)
M(n,d) = multiplicationsቀn+ dn ቁ
x1
x2
x3
1 2 2 x1
x2
x3
0 1 3
目標 A 、 B 為兩種 monotone n 項多項式 degree ≤
d 的排列方法 找出一組 A 、 B
使得 A+B 為一種 n 項多項式 degree ≤ d 的排列方法 目標 : |A| 、 |B| ≤
ටቀn+ dn ቁ. (nd)o(1)
方法 令 A = M(S,d/2) B = M(T,d/2) |S| = |T| = (n+1)/2 |S ∩T| = 1
s
x1x2x3 ……. xn
α α α α α α β β β β β
x1x2x3 ……. xn
α α α α α α β β β β β
T
|S| = |T| = (n+1)/2 |S ∩T| = 1
S (n+1)/2 T
S ∩T
成果 A = M(S,d/2) B = M(T,d/2)
|S| = |T| = (n+1)/2
代入 M(n,d) =
M((n+1)/2,d/2) = ≤ ≤
滿足目標 : |A| 、 |B| ≤
ቀn+ dn ቁ
൬(n+ d+ 1)/2d/2 ൰
ටቀn+ d+ 1d ቁ
(n+ d)1 2Τ .ටቀn+ dd ቁ
ටቀn+ dn ቁ. (nd)o(1)