Fortran - Segmentatation fault (core dumped) -

this kind of follow questions fortran array dynamic size, easy r function seq() , asked previoulsy, in sense still same error when run program:

program received signal sigsegv: segmentation fault - invalid memory reference.  backtrace error: #0  0x7f13e6fd87d7 #1  0x7f13e6fd8dde #2  0x7f13e6929fef #3  0x4014b6 in fillmatrix_ #4  0x40270e in main__ @ dyn.f90:? segmentation fault (core dumped) 

i made slight changes program:

program dyn implicit none real(kind=8), allocatable    :: k(:), tt1(:), p(:)       real(kind=8), allocatable    :: fitness(:,:), k_opt(:,:)                real(kind=8)                 :: dk = 0.1, dp = 0.1       integer                      :: j,l,m,lk,lp,lt           external                         :: derivate, fillmatrix     k = 0.1*dk*[(j,j=0,999)]   ! vector of basal expression levels p = 0.4*dp*[(l,l=1,1000)]  ! vector of period lengths tt1 = 0.1*dk*[(m,m=0,999)] ! vector of values t1/t  lk = size(k) lp = size(p) lt = size(tt1)  call fillmatrix(k,p,tt1,lk, lp, lt, fitness, k_opt)  end program dyn   subroutine fillmatrix(k,p,tt1,size_k, size_p, size_tt1, fitness, k_opt)     implicit none     integer, intent(in)          :: size_k, size_p, size_tt1     real(kind=8)                 :: k(size_k), p(size_p), tt1(size_tt1)     real(kind=8), allocatable    :: results(:), t(:)     real(kind=8)                 :: num = 10, t0,t1,t2,t3              real(kind=8)                 :: periode, laenge, basal, lenge      real(kind=8)                 :: dt = 0.1     real(kind=8), dimension(6)   :: q0, x_new, res                    real(kind=8), dimension(6)   :: u0,f1,f2,f3,u1, k1,k2,k3,k4        real(kind=8), dimension(size_k,size_tt1), intent(out)   :: fitness     real(kind=8), dimension(size_p, size_tt1), intent(out)  :: k_opt     integer                      :: i,j,l,m,n,o,q,r,posi                open(unit = 10,file = '3d.txt', status = 'unknown') ! save data in .txt file     n=1, size(p)     periode = p(n)        ! set period length      o=1,size(tt1)         laenge = tt1(o)   ! set turning point t1/t          q=1,size(k)             basal = k(q)  ! set level of basal expression              lenge = 10*num*periode                      t = 0.1*dt*[(i,i=0,int(lenge))]              ! initial conditions vector q0             q0(1) = 0     ! x             q0(2) = basal ! y             q0(3) = 0     ! z             q0(4) = 0     !             q0(5) = 1     ! b             q0(6) = 0     ! w              x_new = q0 ! set initial conditions               r = 1, size(t)                 call derivate(basal,periode,laenge,t(r),x_new,k1)                   t1 = t(o) + dt/2                       f1 = x_new + (dt*k1)/2                 call derivate(basal,periode,laenge,t1,f1,k2)                        t2 = t(o) + dt/2                       f2 = x_new + (dt*k2)/2                 call derivate(basal,periode,laenge,t2,f2,k3)                        t3 = t(o) + dt                 f3 = x_new + (dt*k3)/2                 call derivate(basal,periode,laenge,t3,f3,k4)                        res = x_new + (dt*(k1+2*k2+2*k3+k4))/6                 if (res(2) < basal)                     res(2) = basal                 endif                 results = res(6)                                      fitness(q,o) = maxval(results)/lenge              end          end         posi = maxloc(fitness(o,:),1)          k_opt(o,n) = k(posi)            end end write(10,*) k_opt               end subroutine fillmatrix 

i have tried find cause of error several hours now, no closer finding it.

at call fillmatrix not of arrays allocated. not legal because explicit size arguments , not have right shape (or shape in fact). case of array fitness , k_opt.

because beginner, couple of advices:

• use debugging options. example, gfortran -wall -fcheck=all -g -fbacktrace.

  for program gfortran writes:

  at line 18 of file test.f90 fortran runtime error: allocatable actual argument 'fitness' not allocated 

  when run program.

• put subroutines module, enable better passing options , checks.

• after did that, use assumed shape arrays (:,:,:) dummy arguments, avoid copies may encounter explicit size.

• do not use real(kind=8), not portable, there many examples here on how that. use named constant, , kind value selected_real_kind() or iso_fortran_env modules constants real32 , real64.