Characteristics polynomial, Fortran

Characteristics polynomial

Real A(3,3),A1(3,3),B(3,3),A2(3,3),D(3,3),E(3,3),A3(3,3)
             Data n/3/
             Data A/1,0,0,0,1,0,0,0,1/
            B0=(-1)**n
             Write(*,*)B0
              k=1
         Call trace(n,A,Bx)
             Do i=1,n
             Do j=1,n
             A1(i,i)=A(i,i)-Bx
             Enddo
             Enddo
             Call multi(n,A,A1,B)
             Bx=Bx/k
             
             Write(*,*)Bx
          k=k+1
          Call trace(n,B,Bx)
             Do i=1,n
             Do j=1,n
             A2(i,i)=B(i,i)-Bx
             Enddo
             Enddo
             Call multi(n,B,A2,D)
             Bx=Bx/k
             Write(*,*)Bx
           k=k+2
          Call trace(n,D,Bx)
             Do i=1,n
             Do j=1,n
             A3(i,i)=D(i,i)-Bx
             Enddo
             Enddo
             Call multi(n,D,A3,E)
             Bx=Bx/k
             Write(*,*)Bx
             
           End

Subroutine trace(n,A, x)
Real A(3,3)
Sum=0
Do i=1,n
Sum=Sum+A(i,i)
Enddo
x=Sum
Return
End
Subroutine Multi(n,P,Q,C)
Real P(3,3),Q(3,3),C(3,3)
Do i=1,n
Do j=1,n
C(i,j)=0.0
Do k=1,n
C(i,j)=C(i,j)+P(i,k)*Q(k,j)
Enddo
Enddo
Enddo
Return
End


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