How can i improve my code

1 次查看（过去 30 天）
Tai-i
Tai-i 2012-7-30
syms E Eg V g;
z=[ ];
y=[ ];
c=3 .*(10.^8);
h=4.1361e-015;
k=8.62E-5;
Tc=300;
for Ei=0.5:0.05:1.3;
z=[ ];
for Eg=1.4:0.01:3.2;
Ec=Eg-Ei;
a = quad( @(E)(E.^2) ./ (exp(E./0.5172)-1), Eg , 100);
aa= quad( @(E)(E.^2) ./ (exp(E./0.5172)-1), Ec , Eg);
for Ucv=Eg-.2:0.005:Eg-.01;
for Uiv=Ei-.1:.005:Ei-.01;
Pin = 1.4458e+026 ;
Uci=Ucv-Uiv;
b = quad(@(E)(E.^2) ./ (exp(( E-Ucv )./0.0259)-1),Eg,100);
bb= quad(@(E)(E.^2) ./ (exp(( E-Uci )./0.0259)-1),Ec,Eg);
if abs(quad( @(E)(E.^2) ./ (exp(E./0.5172)-1), Ei , Ec)- quad(@(E)(E.^2) ./ (exp(( E-Uiv )./0.0259)-1),Ei,Ec)-...
aa+bb) <= 10^-3
P = ( 2.*Ucv./6.3682e-027 ) .* ( a + aa - b - bb ) ./ Pin
z = [z P]
m = max(z)
end
end
end
end
y=[y m]
end
Ei=0.5:0.05:1.3;
plot(Ei,y,'b')
xlabel('Ei');
ylabel('η[%]');
it have to spend 4~5 hours , how can i improve so that more efficiency ?

请先登录，再回答此问题。

回答（3 个）

Jan
Jan 2012-7-30
I did not work with symbolic math in Matlab yet. Therefore I have a silly question:
syms E Eg
...
for Eg=1.4:0.01:3.2
...
b = quad(@(E)(E.^2) ./ (exp(( E-Ucv )./0.0259)-1),Eg,100)
  1. Is is the symbolic type for Eg useful, when it is a counter in a FOR loop? Or is the type ignored and Eg is a double?
  2. When quad operates on an anonymous function, which contains a symbolic variable, is the quadrature computed symbolically?
  3. Isn't it possible and much faster to solve the integral over an exponential function manually?
  4. The repeated growing of z and y is a bad idea, look for "pre-allocation" in this forum. Even MLint should display a corresponding warning, which should be considered carefully. But I assume, that profile will show, that this is not the bottleneck, but the symbolic (?) quad s are more expensive.
  1 个评论
Walter Roberson
Walter Roberson 2012-7-30
When a name is used in an anonymous function dummy argument, the situation is equivalent to using it as an input argument name in a "real" function -- that is, whatever value or type the name has in the surrounding expression is ignored.
When a name has been declared through syms and then that same name is used as the loop index variable in a "for" loop, the names existence as a symbolic variable is forgotten (except that if any constraints had been put on the name, the constraints might be properly erased.)

请先登录，再进行评论。

Walter Roberson
Walter Roberson 2012-7-30
One kind of thing to look for:
The code line
b = quad(@(E)(E.^2) ./ (exp(( E-Ucv )./0.0259)-1),Eg,100);
does not depend upon the value of Uiv, so you can calculate the value before you start the "for Uiv" loop.
Rahul Kashyap
Rahul Kashyap 2012-7-30
try to make the divisions smaller. you have the following statements:
for Ei=0.5:0.05:1.3;
for Eg=1.4:0.01:3.2;
for Ucv=Eg-.2:0.005:Eg-.01;
for Uiv=Ei-.1:.005:Ei-.01;
replace the above lines with:
for Ei=0.5:0.5:1.3;
for Eg=1.4:0.1:3.2;
for Ucv=Eg-.2:0.5:Eg-.01;
for Uiv=Ei-.1:.5:Ei-.01;
this will decrease the iterations. although, its a trade off between accuracy but you should give it a try. if we use your code, the loop will run 17x181x39x19 times, but if you try my statements it will run for 19x2 times. give it a try :)

类别

在 Help Center 和 File Exchange 中查找有关 Assumptions 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by