你知道为什么最小系统中的CPU时间小于原始CPU时间吗？ MATLAB

Question

我有一个程序，用于计算原始系统中的CPU时间和最小的CPU时间。假设CPU_minimum＆lt; CPU_original 但在我的情况下发生相反的情况。这是代码

    clear


load('C.mat');

load('G.mat');

 % start of simulation time for the original state-space model
tic;   


t1 = cputime;

  A = -C\ G;
  BB=sparse(280,4);  
  BB(4,1) = 1;
  BB(6,2)= 1;
  BB(43,3)=1;
  BB(72,4) = 1;

  %disp(BB);

  B =  C\BB;
  C=B';
  D =zeros(4,4);

  sys1 = ss(A,B,C,D)



  totalCPUTime1 = cputime-t1

    fprintf ( 1, 'Creation of the original state-space model needs %1.3f 
   seconds   the CPU.\n', totalCPUTime1 )

  % end of simulation time for original state-space model

  first = toc


   % start of simulation time for the minimum  state-space model
   tic;


    t2 = cputime;
   syss1 = minreal(sys1)


   totalCPUTime2 = cputime-t2

    fprintf ( 1, 'Creation of the minimum state-space model needs %1.3f 
   seconds   the CPU.\n', totalCPUTime2 )


    % end of simulation time for minimum original state-space model
    second = toc

我得到以下CPU时间：

    totalCPUTime1= 3.744
    totalCPUTime2= 9.641

你知道问题出在哪里吗？