数值计算,例如微积分、微分方程求解等存在大量的函数调用,故高效的函数调用对数值计算软件来讲是至关重要的。( h, o0 ~- ^/ h5 y
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Matlab 2009a的测试代码:
f=@(x,y,z,t)x+y+z; & Z8 {' c% @6 d- ~% a
tic;. z. x q i4 i; G }1 f
s=0; w& f1 s) R' N9 E
for x=0:1000! w0 c! Y! X5 D3 v% N0 s1 O
for y=0:100 , n; q0 | j+ K+ m\" l' I$ `
for z=0:100 |# m# [/ |# z9 G. O
s=s+f(x,y,z); * H! I) P3 [ K1 j! m, a
end + D( C, o/ ?, I4 d8 f h
end' k& ^\" r\" T5 \( L
end ) F, k, t: D\" `\" F* _/ u/ h
s! b4 B, L5 H& Z3 x+ V1 Y
toc + w5 |& t5 e) o m$ M
% n! e. W& R* s1 ?
s = # B5 g G3 N& q* h
6.126720600000000e+009 0 Z& p A% \$ D! _
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Elapsed time is 9.546717 seconds.
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发现将函数写成m文件后效率会提高,如下例:4 H1 D2 L( g- x7 K( e0 l
m函数:
%file xyz.m ( p8 d% b7 d; Q& f5 q# v+ Z
function c=xyz(x,y,z)1 j+ I7 _1 Y$ J
c=x+y+z;7 A5 `9 A& M6 W. J$ |% b
end
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测试代码:
tic; + i: E$ e8 Y1 @: z- K9 F
s=0; * O* A) [/ {3 c0 d
for x=0:1000 6 z- N& \6 y* Z3 X1 _
for y=0:1002 I0 K$ b6 g% W( s/ E. V2 c
for z=0:100 . I, }; a! R0 `
s=s+xyz(x,y,z); 5 N+ c% c+ w) V1 t6 i |
end( R2 N7 Q! [8 u% y
end ' x8 B' S5 ^5 Q3 O3 ]2 U: G
end& r# ~) R3 m$ w; f- S
s , S2 r2 o9 }8 V! `/ Q! C
toc- X' h% y4 ]- [$ f) \2 T' t6 c
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s = ! P/ @) B\" F3 Q, @# i\" }; ?' d) {% s
6.126720600000000e+009' ^' a) |5 Y4 m- o- n0 C. @
\" l$ [1 p; D( J% Z
Elapsed time is 4.724592 seconds.
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Forcal 9(OpenFC演示)代码:
f(x,y,z)=x+y+z; % S, |3 f/ F5 z% @: c( U
mvar:; f9 W! g8 Q9 @8 Y8 Z
t=sys::clock(),1 n; U8 |\" s4 j& n
s=0, 8 j0 C' L+ \$ ]& @\" m
x=0, while{x<=1000,6 v7 R' g5 H% W/ ~7 w) k ^) S8 w