MATLAB: Subs Function Memory Leak

leakMATLABmemorymemory leaksubssubs function

Hi, I'm running a function (for discussion purposes I'll call it myfun.m) which utilizes both "solve()" and "subs()" function. Multiple runs of the myfun causes longer and longer execution times. I believe this issue is some sort of memory leak. If I close out of Matlab, open it back up, and execute myfun, it runs at the normal speed. If I continue executing it over and over it then begins to slow down. I was running 2007, but I'm upgrading to 2010. Has this problem been fixed? Is there some sort of clear function I can use that preserves my variables but clears whatever objects are being generated by subs or solve?

Best Answer

solve() uses mupad which has its own memory area. Try using

reset(symengine)

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 clc; clear; close all;
          format long 
          Ma=.84
          Ra=.287
          Rg=.287
          siga=1.4
          sigg=1.3333
          Pa=54.05
          Ta=225.7
          OPR=2:3:200
          tsfc=cell(1,67) ;      %PRE-ALLOCATION
          for i = 1:numel(OPR)
          Va=Ma*sqrt(siga*Ra*Ta)
          Cpoa= (siga*Ra)./(siga - 1)
          TINT = 1100:100:1800
          PRC = sqrt(OPR(i))
          % Diffuser
          efd=.93
          To1 = Ta*(1+((siga-1)/2)*(Ma^2))
          Toa=To1
          Po1 = Pa*(1 + efd*((siga - 1)/2)*(Ma^2))^(siga/siga-1)
          Poa=Pa*(Toa/Ta)^(siga/siga-1)
          %Compressors  
          efc=.87
          %Low Pressure
          Po2=Po1.*(PRC)
          To2 = To1 + ((To1*((PRC.^((siga-1)/siga)-1)))/efc)
          WC_LP = Cpoa*(To1-To2)
          %High Pressure
          To3 = To2 + ((To2.*((PRC.^((siga-1)/siga)-1)))/efc)
          Po3=Po2.*(PRC)
          WC_HP = Cpoa*(To2-To3)
          %Combustion
          efb =.98
          deltPob = .4 
          Po4= (1-deltPob)*Po3
          To4=TINT
          %Combustion Calculations for f
          MC=14.4
          MH=24.9
          MO=0
          Ycc=MC + (MH/4)- (MO/2)
          Tp=To4
          Tr=To3
          To= 298
          HRP_to = -8561991.6
          if Tp <= 1600
          hco2p = 56835 + 66.27*Tp + -11634.0*log(Tp)
          hh2op = 88923 + 49.36*Tp + -7940.8*log(Tp)
          hn2p= 31317 + 37.46*Tp + -4559.3*log(Tp)
          ho2p = 43388 + 42.27*Tp + -6635.4*log(Tp)
          else
          hco2p = 93048 + 68.58*Tp + -16979.0*log(Tp)
          hh2op = 154670 + 60.43*Tp + -19212.0*log(Tp)
          hn2p = 44639 + 39.32*Tp + -6753.4*log(Tp)
          ho2p =127010 + 46.25*Tp + -18798*log(Tp)   
          end
          if Tr <= 1600
          hco2r = 56835 + 66.27*Tr + -11634.0*log(Tr)
          hh2or = 88923 + 49.36*Tr + -7940.8*log(Tr)
          hn2r= 31317 + 37.46*Tr + -4559.3*log(Tr)
          ho2r = 43388 + 42.27*Tr + -6635.4*log(Tr)
          else
          hco2r = 93048 + 68.58*Tr + -16979.0*log(Tr)
          hh2or = 154670 + 60.43*Tr + -19212.0*log(Tr)
          hn2r = 44639 + 39.32*Tr + -6753.4*log(Tr)
          ho2r =127010 + 46.25*Tr + -18798*log(Tr)
          end
          hco2 = hco2p-hco2r
          hh2o = hh2op-hh2or
          hn2 = hn2p-hn2r
          ho2 =ho2p-ho2r
          h2oa=30.5
          h2ob=.0103
          co2a=28.8
          co2b=.028
          o2a=27
          o2b=.0079
          fuela= 38.1
          fuelb=.656
          Delt_HRP = (MH/2)*(h2oa*Tr +.5*h2ob*Tr.^2) - (h2oa*To +.5*h2ob*To.^2)+MC*(co2a*Tr +.5*co2b*Tr.^2) - (co2a*To +.5*co2b*To.^2)- Ycc*(o2a*Tr +.5*o2b*Tr.^2) - (o2a*To +.5*o2b*To.^2)-(fuela*Tr +.5*fuelb*Tr.^2) - (fuela*To +.5*fuelb*To.^2)
          HRP =HRP_to + Delt_HRP
          y = (-HRP - MC*hco2 - (MH/2).*hh2o + Ycc.*ho2)./(3.76.*hn2+ho2)
          fideal=197.7./(4.76*y*28.97)
          f=fideal*efb
          %Turbines | HIgh and Low have equal efficiencies 
          eft=.90
          efm=.99
          Cpog = (sigg*Rg)/(sigg-1)
          % High Pressure
          To5= To4 + (WC_HP./(efm*(1+f)*Cpog))
          Po5 = Po4*(1-((1-(To5/To4))/eft))^(sigg/(sigg-1))
          % Low Pressure
          To6= To5 + (WC_LP./(efm*(1+f)*Cpog))
          Po6 = Po5*(1-((1-(To6/To5))/eft))^(sigg/(sigg-1))
          %Nozzle
          %Choke Test
          efn = .95
          P_Po6 = (1-((1/efn)*(1-(2/(sigg+1)))))^(sigg/(sigg-1))
          R=Pa./Po6
          Me=1
          Pe=Po6*(P_Po6)
          Te=To6*(2/(sigg+1))
          roe= Pe./(Rg*Te)
          Ve= Me*sqrt(sigg*Rg*1000*Te)
          % Fs and T.S.F.C Calculations
          Fs = ((1+f).*Ve-Va) + (Pe-Pa).*((1+f)./(roe.*Ve))
          tsfc{i}= (f./Fs).*3600;
          end
          celldisp(tsfc)        %each subcell represents each value of OPR
tsfc = vertcat(tsfc{:})    %double array

MATLAB: Can’t figure out how to finalize the code

%V1=volume of first reactor in L
%V2=volume of second reactor in L
%V3=volume of third reactor in L
%V4=volume of forth reactor in L
 
%k1=first order reaction rate in units of (L^3)(M^-1)(T^-1)
%k2=second order reaction rate in units of (L^3)(M^-1)(T^-1)
%Each reactor has different reaction rate
 
%M=mass in units of M
%Qin=inflow in units of (L^3)(T^-1)
%Qout=outflow in units of (L^3)(T^-1)
%Qxy=the flow from reactor x to reactor y (x&y can be 1,2,3..)
%UNITS
%The unit for V1, V2, V3 & V4 is L
%The unit for k1 is hr^-1
%The unit for k2 is L/(mg*hr)
%The unit for M is mg
%The unit for Qin, Qout,Q12, Q23, Q34, Q32, Q43 & Qxy is L/hr
%Given and calculated values  
Qin=10;
Q12=10;
Q23=10+5; %Q23=Q12+Q32
Q34=15-5+3; %Q34=Q23-Q32+Q43
Qout=10;
Q32=5;
Q43=3;
 
Cain=1;
Cbin=0;
 
V1=25;
V2=75;
V3=100;
V4=25;
 
k11=0.05;
k12=0.1;
k13=0.5;
k14=0.1;
 
k21=0.04;
k22=0.08;
k23=0.4;
k24=0.08;
 
%% PARTA
 
%Mass Balance Eqns for Chemical Species A
 
%For reactor 1

%(Qin*Cain)-(Q12*Ca1)-(k11*Cain*V1)==0  %for first order reaction
%(Qin*Cain)-(Q12*Ca1)-(k21*(Cain)^2*V1)==0  %for second oreder reaction
 
%For reactor 2

%(Q12*Ca1)+(Q32*Ca3)-(Q23*Ca2)-(k12*Ca2*V2)==0 %for first order reaction
%(Q12*Ca1)+(Q32*Ca3)-(Q23*Ca2)-(k22*(Ca2)^2*(V2))==0 %for second oreder reaction
 
%For reactor 3

%(Q23*Ca2)+(Q43*Ca4)-(Q32*Ca3)-(Q34*Ca3)-(k13*Ca3*V3)==0  %for first order reaction
%(Q23*Ca2)+(Q43*Ca4)-(Q32*Ca3)-(Q34*Ca3)-(k23*(Ca3)^2*(V3))==0  %for second order reaction
 
%For reactor 4

%(Q34*Ca3)-(Q43*Ca4)-(Qout*Ca4)-(k14*Ca4*V4)==0  %for first order reaction
%(Q34*Ca,3)-(Q43*Ca,4)-(Qout*Ca,4)-(k24*(Ca4)^2*V4)==0  %for second order reaction
 
%Mass Balance Eqns for Chemical Species B
 
%For reactor 1
%(Qin*Cbin)-(Q12*Cb1)+(k11*Ca1*V1)==0  %for first order reaction
%(Qin*Cbin)-(Q12*Cb1)+(k21*(Ca1)^2*V1)==0  %for second oreder reaction
 
%For reactor 2
%(Q12*Cb1)+(Q32*Cb3)-(Q23*Cb2)+(k12*Ca2*V2)==0 %for first order reaction
%(Q12*Cb1)+(Q32*Cb3)-(Q23*Cb2)+(k22*(Ca2)^2*(V2))==0 %for second oreder reaction
 
%For reactor 3
%(Q23*Cb2)+(Q43*Cb4)-(Q32*Cb3)-(Q34*Cb3)+(k13*Ca3*V3)==0  %for first order reaction
%(Q23*Cb2)+(Q43*Cb4)-(Q32*Cb3)-(Q34*Cb3)+(k23*(Ca3)^2*(V3))==0  %for second order reaction
 
%For reactor 4
%(Q34*Cb3)-(Q43*Cb4)-(Qout*Cb4)+(k14*Ca4*V4)==0  %for first order reaction
%(Q34*Cb3)-(Q43*Cb4)-(Qout*Cb4)+(k24*(Ca4)^2*V4)==0  %for second order reaction
 
syms Ca1 Ca2 Ca3 Ca4 Cb1 Cb2 Cb3 Cb4
Eqns_1st_Order=[(Qin*Cain)-(Q12*Ca1)-(k11*Cain*V1)%=0















(Q12*Ca1)+(Q32*Ca3)-(Q23*Ca2)-(k12*Ca2*V2)%=0
(Q23*Ca2)+(Q43*Ca4)-(Q32*Ca3)-(Q34*Ca3)-(k13*Ca3*V3)%=0
(Q34*Ca3)-(Q43*Ca4)-(Qout*Ca4)-(k14*Ca4*V4)%=0
(Qin*Cbin)-(Q12*Cb1)+(k11*Cain*V1)%=0
(Q12*Cb1)+(Q32*Cb3)-(Q23*Cb2)+(k12*Ca2*V2)%=0
(Q23*Cb2)+(Q43*Cb4)-(Q32*Cb3)-(Q34*Cb3)+(k13*Ca3*V3)%=0
(Q34*Cb3)-(Q43*Cb4)-(Qout*Cb4)+(k14*Ca4*V4)]%=0
Eqns_1st_Order = 
 
Eqns_2nd_Order=[(Qin*Cain)-(Q12*Ca1)-(k21*(Cain)^2*V1)%=0
(Q12*Ca1)+(Q32*Ca3)-(Q23*Ca2)-(k22*(Ca2)^2*(V2))%=0
(Q23*Ca2)+(Q43*Ca4)-(Q32*Ca3)-(Q34*Ca3)-(k23*(Ca3)^2*(V3))%=0
(Q34*Ca3)-(Q43*Ca4)-(Qout*Ca4)-(k24*(Ca4)^2*V4)%=0
(Qin*Cbin)-(Q12*Cb1)+(k21*(Cain)^2*V1)%=0
(Q12*Cb1)+(Q32*Cb3)-(Q23*Cb2)+(k22*(Ca2)^2*(V2))%=0
(Q23*Cb2)+(Q43*Cb4)-(Q32*Cb3)-(Q34*Cb3)+(k23*(Ca3)^2*(V3))%=0
(Q34*Cb3)-(Q43*Cb4)-(Qout*Cb4)+(k24*(Ca4)^2*V4)]%=0
Eqns_2nd_Order = 
sol = solve(Eqns_2nd_Order, [Ca1 Ca2 Ca3 Ca4 Cb1 Cb2 Cb3 Cb4])
sol = struct with fields:
    Ca1: [8×1 sym]
    Ca2: [8×1 sym]
    Ca3: [8×1 sym]
    Ca4: [8×1 sym]
    Cb1: [8×1 sym]
    Cb2: [8×1 sym]
    Cb3: [8×1 sym]
    Cb4: [8×1 sym]
sol.Ca1
ans = 
sol.Ca2
ans = 
vpa(sol.Ca2, 3)
ans =

Best Answer

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