# Speed up MatlabFunction or use alternatives

조회 수: 7(최근 30일)
Finn Busch 2020년 4월 17일
답변: Steven Lord 2022년 11월 28일
Hello,
I am currently processing a big equation (in fact a 36 - Vector with ~15.000 characters each) and am trying to get a function using MatlabFunction. The goal is to receive a function which can be evaluated as quickly as possible, as it's part of a system solved by an ODE solver. The equation itself only contains polynomials to the degree of 3 and square-roots (^3/2 e.g.) but no sin, cos, etc. . Calling MatlabFunction took longer than 18 Hours, and now I had to change the equation and I really don't want to wait for the full 18 Hours. Is setting optimize to false advisable, or will this make my evaluation time worse? Are there other options beside MatlabFunction? I am not very familiar with this kind of stuff as I never had to deal with calculations taking so long.
Any help is greatly appreciated!
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Franz Enkelmann 2022년 11월 28일
Have you just found a solution?

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### 답변(1개)

Steven Lord 2022년 11월 28일
Have you tried telling matlabFunction to skip trying to Optimize the code?
cd(tempdir)
syms a b c d positive
syms x
s = solve(a*x^3+b*x^2+c*x+d == 0, x, MaxDegree=3);
s is a pretty complicated expression, but the final answer can be simplified through the use of temporary sub-expressions. But that simplification can result in longer files (albeit with simpler expressions and shorter lines) and longer time creating the files.
tic
matlabFunction(s, File='cubicSolver1.m', Optimize=true);
toc
Elapsed time is 0.477392 seconds.
dbtype cubicSolver1.m
1 function s = cubicSolver1(a,b,c,d) 2 %cubicSolver1 3 % S = cubicSolver1(A,B,C,D) 4 5 % This function was generated by the Symbolic Math Toolbox version 9.2. 6 % 28-Nov-2022 14:57:43 7 8 t2 = b.^2; 9 t3 = b.^3; 10 t4 = 1.0./a; 11 t7 = sqrt(3.0); 12 t5 = t4.^2; 13 t6 = t4.^3; 14 t8 = (b.*t4)./3.0; 15 t9 = (c.*t4)./3.0; 16 t10 = (d.*t4)./2.0; 17 t11 = -t8; 18 t12 = -t10; 19 t13 = (b.*c.*t5)./6.0; 20 t15 = (t2.*t5)./9.0; 21 t16 = (t3.*t6)./2.7e+1; 22 t14 = -t13; 23 t17 = -t15; 24 t18 = -t16; 25 t19 = t9+t17; 26 t21 = t10+t14+t16; 27 t20 = t19.^3; 28 t22 = t21.^2; 29 t23 = t20+t22; 30 t24 = sqrt(t23); 31 t25 = t12+t13+t18+t24; 32 t26 = t25.^(1.0./3.0); 33 t27 = 1.0./t26; 34 t28 = t26./2.0; 35 t29 = -t28; 36 t30 = t19.*t27; 37 t31 = t30./2.0; 38 t32 = t26+t30; 39 t33 = t7.*t32.*5.0e-1i; 40 s = [t11+t26-t30;t11+t29+t31-t33;t11+t29+t31+t33];
tic
matlabFunction(s, File='cubicSolver2.m', Optimize=false);
toc
Elapsed time is 0.121004 seconds.
dbtype cubicSolver2.m
1 function s = cubicSolver2(a,b,c,d) 2 %cubicSolver2 3 % S = cubicSolver2(A,B,C,D) 4 5 % This function was generated by the Symbolic Math Toolbox version 9.2. 6 % 28-Nov-2022 14:57:43 7 8 et1 = (c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).*1.0./((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0); 9 et2 = ((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0); 10 et3 = ((c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).*1.0./((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0))./2.0+sqrt(3.0).*(et1+et2).*5.0e-1i-b./(a.*3.0); 11 et4 = ((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0).*(-1.0./2.0); 12 et5 = (c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).*1.0./((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0); 13 et6 = ((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0); 14 et7 = ((c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).*1.0./((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0))./2.0-sqrt(3.0).*(et5+et6).*5.0e-1i-b./(a.*3.0); 15 et8 = ((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0).*(-1.0./2.0); 16 et9 = -(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).*1.0./((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0)-b./(a.*3.0); 17 et10 = ((d.*(-1.0./2.0))./a-(1.0./a.^3.*b.^3)./2.7e+1+sqrt((d./(a.*2.0)+(1.0./a.^3.*b.^3)./2.7e+1-(1.0./a.^2.*b.*c)./6.0).^2+(c./(a.*3.0)-(1.0./a.^2.*b.^2)./9.0).^3)+(1.0./a.^2.*b.*c)./6.0).^(1.0./3.0); 18 s = [et9+et10;et7+et8;et3+et4];

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