# Type mismatch error when calling a subroutine **URL:** \ **Category:** Help\ **Created:** [August 28, 2021, 10:08am UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760 "2021-08-28T10:08:35Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![haidangwy](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/haidangwy/32/732_2.png) [@haidangwy](https://fortran-lang.discourse.group/u/haidangwy)\ **Post date:** [August 28, 2021, 10:08am UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/1 "2021-08-28T10:08:35Z")
Hi! everybody. In the last topic, I asked for help to find the roots of a nonlinear function. Today, I get into trouble with interpolation. I don’t know why it doesn’t work. I use subroutines spline and splint from Fortran 95 recipe. but the compiler checking said that it has errors: "type mismatch in Fortran Here are my code: ```auto program test_28_08 implicit none integer, parameter :: nc=1001 integer, parameter :: ni=1000 double precision xmin, xmax double precision xi(ni), yi(ni) double precision y2 double precision step, deriv3 double precision yp1,ypn,r,y integer i, step1 common A,Z,R0,am real A,Z,R0,am double precision:: Vn,Vc,Vl double precision rmin,rmax c--------------------------------------------------------- input array ! input parameter A=102.0d+00 Z=50.0d+00 R0=1.25*A**0.3333333 write(*,*) 'nuclear radius' ,R0 am=931.5*A*4.0/(A+4.0) !average mass write(*,*) 'average mass', am xmin = 0.1d+00 xmax = 100.0d+00 ! generate xi,yi step =(xmax-xmin)/float(nc-1) do i=1,ni r=xmin+step*dfloat(i) call compute_Vn(r,Vn) call compute_Vc(r,Vc) call compute_Vl(r,Vl) xi(i)=step*dfloat(i) yi(i)=Vl+Vc+Vn end do ! output data into a file open(1,file='out_table.dat',status='unknown') do i=1,ni write(1,*) xi(i),yi(i) end do close(1) write(*,*) 'array is created' c--------------------------------------------------------first integrate ! step 2: calculate derivatives rmin=xi(1) rmax=xi(ni) yp1 = deriv3(xmin, xi, yi, ni, 1) ypn = deriv3(xmax, xi, yi, ni, 1) write (*,201) rmin,yp1,rmax,ypn 201 format (7f12.5) c------------------------------------------------------------spline call spline(xi,yi,ni,yp1,ypn,y2) c-----------------------------------------------------splint + integrate step1=nint((4.587679-0.022480)/ni) do i =1,(step1-1) r=step*dfloat(i) call splint(xi,yi,y2,ni,r,y) write (*,*) y end do end program test_28_08 c-----------------------subroutine------------------------ ! Function f(x) to get derivation function deriv3(xx, xi, yi, ni, m) implicit none integer, parameter :: n=3 double precision deriv3, xx integer ni, m double precision xi(ni), yi(ni) double precision x(n), f(n) integer i, j, k, ix ! exit if too high-order derivative was needed, if (m > 2) then deriv3 = 0.0 return end if ! if x is ouside the xi(1)-xi(ni) interval set deriv3=0.0 if (xx < xi(1) .or. xx > xi(ni)) then deriv3 = 0.0 return end if ! a binary (bisectional) search to find i so that xi(i-1) < x < xi(i) i = 1 j = ni do while (j > i+1) k = (i+j)/2 if (xx < xi(k)) then j = k else i = k end if end do ! shift i that will correspond to n-th order of interpolation ! the search point will be in the middle in x_i, x_i+1, x_i+2 ... i = i + 1 - n/2 ! check boundaries: if i is ouside of the range [1, ... n] -> shift i if (i < 1) i=1 if (i + n > ni) i=ni-n+1 ! just wanted to use index i ix = i ! initialization of f(n) and x(n) do i=1,n f(i) = yi(ix+i-1) x(i) = xi(ix+i-1) end do ! calculate the first-order derivative using Lagrange interpolation if (m == 1) then deriv3 =(2.0*xx - (x(2)+x(3)))*f(1)/((x(1)-x(2))*(x(1)-x(3))) deriv3 = deriv3 + (2.0*xx - (x(1)+x(3)))*f(2)/((x(2)- 1 x(1))*(x(2)-x(3))) deriv3 = deriv3 + (2.0*xx - (x(1)+x(2)))*f(3)/((x(3)- 2 x(1))*(x(3)-x(2))) ! calculate the second-order derivative using Lagrange interpolation else deriv3 = 2.0*f(1)/((x(1)-x(2))*(x(1)-x(3))) deriv3 = deriv3 + 2.0*f(2)/((x(2)-x(1))*(x(2)-x(3))) deriv3 = deriv3 + 2.0*f(3)/((x(3)-x(1))*(x(3)-x(2))) end if end function deriv3 c-------------------------------------COMPUTE POTENTIAL WITH CONDITIONS !-------------------------------------------------------------------- subroutine compute_Vn(r,Vn) implicit none double precision r,Vn real::A,Z,R0,am common A,Z,R0,am Vn=-50.0/(1.0+exp((r-R0)/0.5)) end subroutine compute_Vn !---------------------------------------------------------------------- subroutine compute_Vc(r,Vc) implicit none double precision:: r,phi,up,Vc real::A,Z,R0,am common A,Z,R0,am if (r.lt.R0) then Vc=(Z*1.44/R0)*(3.0-(r/R0)**2.0) else if (r.gt.R0) then Vc=2.88*Z/r else if (r.eq.R0) then phi=1.5d0/R0 up=phi*r Vc=(Z*2.88/R0)*(1-exp(-up-0.5*(up**2.0)-0.35*(up**3.0))) end if end subroutine compute_Vc !---------------------------------------------------------------------- subroutine compute_Vl(rr,Vl) implicit none double precision rr,Vl real::A,Z,R0,am common A,Z,R0,am real,parameter:: hbarc =197.33 Vl=((hbarc)**2.0)/(8.0*am*rr**2.0) end subroutine compute_Vl c--------------------------------- c----------------------------------------------------------------spline from F95. recipe SUBROUTINE spline(x,y,n,yp1,ypn,y2) implicit none INTEGER n,NMAX REAL yp1,ypn,x(n),y(n),y2(n) PARAMETER (NMAX=1000) INTEGER i,k REAL p,qn,sig,un,u(NMAX) if (yp1.gt..99e30) then y2(1)=0. u(1)=0. else y2(1)=-0.5 u(1)=(3./(x(2)-x(1)))*((y(2)-y(1))/(x(2)-x(1))-yp1) endif do i=2,n-1 sig=(x(i)-x(i-1))/(x(i+1)-x(i-1)) p=sig*y2(i-1)+2. y2(i)=(sig-1.)/p u(i)=(6.*((y(i+1)-y(i))/(x(i+1)-x(i))-(y(i)- 1 y(i-1))/(x(i)-x(i-1)))/(x(i+1)-x(i-1))-sig*u(i-1))/p end do if (ypn.gt..99e30) then qn=0. un=0. else qn=0.5 un=(3./(x(n)-x(n-1)))*(ypn-(y(n)-y(n-1))/(x(n)-x(n-1))) endif y2(n)=(un-qn*u(n-1))/(qn*y2(n-1)+1.) do k=n-1,1,-1 y2(k)=y2(k)*y2(k+1)+u(k) enddo return END SUBROUTINE spline C--------------------------------------------------------------splint from F95. recipe SUBROUTINE splint(xa,ya,y2a,n,x,y) implicit none INTEGER n REAL x,y,xa(n),y2a(n),ya(n) INTEGER k,khi,klo REAL a,b,h klo=1 khi=n 1 if (khi-klo.gt.1) then k=(khi+klo)/2 if(xa(k).gt.x)then khi=k else klo=k endif goto 1 endif h=xa(khi)-xa(klo) if (h.eq.0.) stop a=(xa(khi)-x)/h b=(x-xa(klo))/h y=a*ya(klo)+b*ya(khi)+ 2 ((a**3-a)*y2a(klo)+(b**3-b)*y2a(khi))*(h**2)/6. return END subroutine splint ``` ---
**Author:** ![vmagnin](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/vmagnin/32/28_2.png) [@vmagnin](https://fortran-lang.discourse.group/u/vmagnin)\ **Post date:** [August 28, 2021, 10:22am UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/2 "2021-08-28T10:22:41Z")
Hi, probably a mismatch between the types send to the subroutines and the types of their dummy arguments. My advice is that you should either put the subroutines in a module, or more simply here use the `CONTAINS` statement and put the subroutines and functions before `END PROGRAM`. It will help the compiler to verify type matches and you should obtain more explicit messages. See [fortran - Contains statement - Stack Overflow](https://stackoverflow.com/questions/35808053/contains-statement) ---
**Author:** ![alozada](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/alozada/32/298_2.png) [@alozada](https://fortran-lang.discourse.group/u/alozada)\ **Post date:** [August 28, 2021, 3:51pm UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/3 "2021-08-28T15:51:50Z")
> [@haidangwy](#): > > I don’t know why it doesn’t work. Fixing the format in line 1 the program works output `nuclear radius 5.84041071 ` `average mass 3585.39624 ` ` array is created` ` 0.09990 -250.27002 99.90000 0.00000` Two warnings about the REAL type (8 → 4) appear on lines 51, 56 ---
**Author:** ![haidangwy](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/haidangwy/32/732_2.png) [@haidangwy](https://fortran-lang.discourse.group/u/haidangwy)\ **Post date:** [August 28, 2021, 11:22pm UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/5 "2021-08-28T23:22:10Z")
Thank you so much, so I need to change the variables to real, is it right? ---
**Author:** ![haidangwy](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/haidangwy/32/732_2.png) [@haidangwy](https://fortran-lang.discourse.group/u/haidangwy)\ **Post date:** [August 28, 2021, 11:36pm UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/6 "2021-08-28T23:36:55Z")
yeah, there are two warnings, that mean it still has mistakes. and it might affect to the result. ---
**Author:** ![FortranFan](https://avatars.discourse-cdn.com/v4/letter/f/96bed5/32.png) [@FortranFan](https://fortran-lang.discourse.group/u/FortranFan)\ **Post date:** [August 29, 2021, 12:37am UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/8 "2021-08-29T00:37:20Z")
@haidangwy , in this [**post**](https://fortran-lang.discourse.group/t/how-can-i-solve-this-equation-which-has-condition/1669/16), you confirmed you were a student and your earlier post was part of an assignment. Will it possible for you to share some details re: the class where you have such assignments? Some questions that come to mind are as follows: is it generally on numeric computing? Or is it specific to Fortran programming? If the former, does the class cover any Fortran language teaching at all or are the language details left up to the students to pick up? And is the choice of the solution paradigm (whether what is currently a compiler-based language such as Fortran or more of a modeling platform such as MATLAB) decided for all the students as part of the class requirements or does each student pick their own choice? The reasons for above questions are some of your Fortran coding practices (or lack thereof) and what might be their origin in this day and age. By the way, are you able to tap into a textbook resource such as [**Fortran for Scientists and Engineers by Chapman, 2018**](https://www.mheducation.com/highered/product/fortran-scientists-engineers-chapman/M9780073385891.html)? I think you will find it very useful to review that book. ---
**Author:** ![haidangwy](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/haidangwy/32/732_2.png) [@haidangwy](https://fortran-lang.discourse.group/u/haidangwy)\ **Post date:** [August 29, 2021, 2:02am UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/9 "2021-08-29T02:02:51Z")
At first, thank you very much. In detail, what I am doing is in the class Nuclear physics at my university. My assignment is to use one of the program to find the half-life of nuclei. So I pick up Fortran because I think I might be appropriate to me. I’m currently watching tutorials on Youtube. I’m to find your book to read. Thank you for your recommendation 🙂 ---
**Author:** ![haidangwy](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/haidangwy/32/732_2.png) [@haidangwy](https://fortran-lang.discourse.group/u/haidangwy)\ **Post date:** [August 29, 2021, 2:05am UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/10 "2021-08-29T02:05:46Z")
that sounds great, let me try. Thank you 😊 ---
**Author:** ![billlong](https://avatars.discourse-cdn.com/v4/letter/b/71e660/32.png) [@billlong](https://fortran-lang.discourse.group/u/billlong)\ **Post date:** [August 30, 2021, 12:50pm UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/11 "2021-08-30T12:50:56Z")
Argument type and kind mismatches are a common programming mistake in Fortran. REAL and DOUBLE PRECISION are both of real type, but the kinds do not match. The suggestion for putting the subroutines in a module or as a contained procedure has the advantage that the compiler can “see” the interface of the called routine when compiling the callers and more likely find the bug at compile time. One the objectives of the proposal for templates in Fortran is to help avoid this problem (if you write the library routine as a template). ---
**Author:** ![haidangwy](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/haidangwy/32/732_2.png) [@haidangwy](https://fortran-lang.discourse.group/u/haidangwy)\ **Post date:** [August 30, 2021, 2:02pm UTC](https://fortran-lang.discourse.group/t/type-mismatch-error-when-calling-a-subroutine/1760/12 "2021-08-30T14:02:58Z")
now i get it, Thank you so much 😊