# How to fix nan diff nan

``````nan != nan diff nan => Sorry error in Optimization (e) add:  int2d(Th,optimize=0)(...)
remark if you add  (..  ,   optimize=2) then  you remove this check (be careful);
current line = 146
Exec error : In Optimized version
-- number :1
Exec error : In Optimized version
-- number :1
err code 8 ,  mpirank 0
``````

the above is the error message and the whole code is

``````load "iovtk"
verbosity=0;
// Parameters
int nn = 15;
int nnPlus = 5;
real l = 1.;
real L = 15.;
real hSlope = 0.1;
real H = 6.;
real h = 0.5;

real beta = 0.01;

real eps = 9.81/303;
real nu = 1.;
real numu = nu/sqrt(0.09);
real nuep = pow(nu,1.5)/4.1;
real dt = 0.;

real Penalty = 1.e-6;

// Mesh
border b1(t=0, l){x=t; y=0;}
border b2(t=0, L-l){x=1.+t; y=-hSlope*t;}
border b3(t=-hSlope*(L-l), H){x=L; y=t;}
border b4(t=L, 0){x=t; y=H;}
border b5(t=H, h){x=0; y=t;}
border b6(t=h, 0){x=0; y=t;}

mesh Th=buildmesh(b1(nnPlus*nn*l) + b2(nn*sqrt((L-l)^2+(hSlope*(L-l))^2)) + b3(nn*(H + hSlope*(L-l))) + b4(nn*L) + b5(nn*(H-h)) + b6(nnPlus*nn*h));
plot(Th);

// Fespaces
fespace Vh2(Th, P1b);
Vh2 Ux, Uy,du1=0,du2=0,uite1=0,uite2=0;
Vh2 Vx, Vy,v1,v2;
Vh2 Upx, Upy=0;
fespace Vh(Th,P1);
Vh p=0, q,pp=p,pite,dp,vp;
Vh Tp, T=35,dT,Tite,vt;
Vh k=log(0.27), kp=k,dk,kite,vk;
Vh ep=log(0.002104), epp=ep,dep,epite,vep;

fespace V0h(Th,P0);
V0h muT=1;
V0h prodk, prode;
Vh kappa=0.25e-4, stress;
// Macro
macro Div(u1,u2) (dx(u1) + dy(u2)) //
// Problem
real alpha = 0.;

// Initialization with stationary solution

// Initialization
dt = 0.05; //probably too big
int nbiter = 1;
real coefdt = 0.25^(1./nbiter);
real coefcut = 0.25^(1./nbiter);
real cut = 0.01;
real tol = 0.5;
real coeftol = 0.5^(1./nbiter);

Tp = T - 10*((x<1)*(y<0.5) + (x>=1)*(y+0.1*(x-1)<0.5));
Upx=0+(x==0)*(y>=0)*(y<=h)*3;
plot(Upx,  cmm=" Ux ", wait=1);
plot(Upy,  cmm=" Ux ", wait=1);
// Convergence loop
real T0 = clock();
cout  << " - dt = " << dt << endl;
alpha = 1/dt;

// Time loop
real t = 0.;
for (int i = 0; i <= 500; i++){
uite1=Upx;
uite2=Upy;
pite=pp;
Tite=Tp;
kite=kp;
epite=epp;

for (int n=0;n<=10;n++){
solve increment ([du1,du2,dp,dT,dk,dep],[v1,v2,vp,vt,vk,vep])
=int2d(Th)(alpha*([du1,du2]'*[v1,v2]-dT*vt-dk*vk-dep*vep)
+(0.09/2)*exp(2*kite-epite)*2*[dx(kite),dy(kite)]'*[dx(dk),dy(dk)]*vk
-(0.09/2)*exp(2*kite-epite)*(2*dk-dep)*[dx(vk),dy(vk)]'*[dx(kite),dy(kite)]-(0.09/2)*exp(2*kite-epite)*[dx(vk),dy(vk)]'*[dx(dk),dy(dk)]
+(0.09/2)*exp(kite-epite)*(4*dx(uite1)*dx(du1)+4*dy(uite2)*dy(du2)+2*(dy(uite1)+dx(uite2))*(dy(du1)+dx(du2)))*vk
+(0.09/2)*exp(kite-epite)*(dk-dep)*(2*dx(uite1)*dx(uite1)+2*dy(uite2)*dy(uite2)+(dy(uite1)+dx(uite2))*(dy(uite1)+dx(uite2)))*vk
-(1.92/2)*exp(-kite+epite)*(dep-dk)*vep
+(0.09/2.6)*exp(2*kite-epite)*(2*dk-dep)*[dx(epite),dy(epite)]'*[dx(epite),dy(epite)]*vep
+(0.09/2.6)*exp(2*kite-epite)*2*[dx(epite),dy(epite)]'*[dx(dep),dy(dep)]*vep
-(0.09/2.6)*exp(2*kite-epite)*(2*dk-dep)*[dx(epite),dy(epite)]'*[dx(vep),dy(vep)]
-(0.09/2.6)*exp(2*kite-epite)*[dx(dep),dy(dep)]'*[dx(vep),dy(vep)]
+((1.44*0.09)/2)*exp(kite-epite)*(4*dx(uite1)*dx(du1)+4*dy(uite2)*dy(du2)+2*(dy(uite1)+dx(uite2))*(dy(du1)+dx(du2)))*vep
+((1.44*0.09)/2)*exp(kite-epite)*(dk-dep)*(2*dx(uite1)*dx(uite1)+2*dy(uite2)*dy(uite2)+(dy(uite1)+dx(uite2))*(dy(uite1)+dx(uite2)))*vep
-0.05*exp(2*kite-epite)*(2*dk-dep)*[dx(vt),dy(vt)]'*[dx(Tite),dy(Tite)]
-0.05*exp(2*kite-epite)*[dx(vt),dy(vt)]'*[dx(dT),dy(dT)]
)
+int1d(Th,b1,b2,b5)(
(0.09/2.6)*2.4952*exp(0.5*kite)*(0.5*dk)*vep
)+int1d(Th,b1,b2)(
0.41*((0.09)^0.25)*0.5*(exp(0.5*kite)*(0.5*dk)*uite1*v1+exp(0.5*kite)*du1*v1)
)+int2d(Th)(
alpha*([uite1-Upx,uite2-Upy]'*[v1,v2]-(Tite-Tp)*vt-(kite-kp)*vk-(epite-epp)*vep)
+(9.81/606)*(Tite+Tp-70)*v2-0.5*(Div(uite1,uite2)+Div(Upx,Upy))*vp
-0.5*exp(epite-kite)*vk-0.5*exp(epp-kp)*vk
+(0.09/2)*exp(kite-epite)*vk*(2*dx(uite1)*dx(uite1)+2*dy(uite2)*dy(uite2)+(dy(uite1)+dx(uite2))*(dy(uite1)+dx(uite2)))
+(0.09/2)*exp(kp-epp)*vk*(2*dx(Upx)*dx(Upx)+2*dy(Upy)*dy(Upy)+(dy(Upx)+dx(Upy))*(dy(Upx)+dx(Upy)))
-1.92*0.5*exp(epite-kite)*vep-1.92*0.5*exp(epp-kp)*vep
+(1.44*0.09/2)*exp(kite-epite)*vep*(2*dx(uite1)*dx(uite1)+2*dy(uite2)*dy(uite2)+(dy(uite1)+dx(uite2))*(dy(uite1)+dx(uite2)))
+(1.44*0.09/2)*exp(kp-epp)*vep*(2*dx(Upx)*dx(Upx)+2*dy(Upy)*dy(Upy)+(dy(Upx)+dx(Upy))*(dy(Upx)+dx(Upy)))
)+int1d(Th,b1,b2,b5)(
(0.09/2.6)*2.4952*exp(0.5*kite)*vep+(0.09/2.6)*2.4952*exp(0.5*kp)*vep)
+int1d(Th,b1,b2)(0.41*((0.09)^0.25)*exp(0.5*kite)*uite1*v1*0.5+0.41*((0.09)^0.25)*exp(0.5*kp)*Upx*v1*0.5)
+on(b5,du1=0,du2=0)
+on(b6,du1=0,du2=0,dep=0,dk=0,dT=0)+on(b2,dT=0)+on(b1,du2=0,dT=0);
uite1=du1+uite1;
uite2=du2+uite2;
pite=dp+pite;
Tite=dT+Tite;
kite=dk+kite;
epite=dep+epite;
}
Upx=uite1;
Upy=uite2;
pp=pite;
Tp=Tite;
kp=kite;
epp=epite;
plot(Upx,  cmm=" Ux ", wait=1);
plot(Upy,  cmm=" Ux ", wait=1);

}
cout << "Total Time = " << clock()-T0 << endl;
``````

line 146 is `+on(b6,du1=0,du2=0,dep=0,dk=0,dT=0)+on(b2,dT=0)+on(b1,du2=0,dT=0);` this code is that realize “large fluid problem” by using central difference and newton method, I want that the velocity u’*n=0 on b2, I don’t know how to fix this error and how to implement u’*n=0 in newton method