# Converting COMMON; am I correct? **URL:** \ **Category:** Uncategorized\ **Created:** [October 21, 2021, 8:36am UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133 "2021-10-21T08:36:40Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![garynewport](https://avatars.discourse-cdn.com/v4/letter/g/898d66/32.png) [@garynewport](https://fortran-lang.discourse.group/u/garynewport)\ **Post date:** [October 21, 2021, 8:36am UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/1 "2021-10-21T08:36:41Z")
Again, sorry but I would like to confirm my understanding, if that is okay. My one include file has the following line… ```auto IMPLICIT DOUBLE PRECISION (A-H,O-Z), INTEGER(I-N) ``` The other included file has this COMMON block… ```auto COMMON/ GIC / X(MJ,MH), VX(MJ,MH), GRV(MJ), & & zM(MJ),dM(MJ),Zmass,Zflux,dflux,xTimod,xCorm, & & TIME,DTIME,FACTIM,DTMIN,DTMAX,CHGMIN,CHGMAX,CHANGE, & & dLmx,dLmn,dPmx,dPmn,dXmn,dXmx,dZmax,dZmin,dZdt, & & dMat,Atmn,TAUx,dPat,RLH,Crad,Cwrk,xH2,ener,Arad3,taujk, & & dTmn,dMix,zMmn,zMmx,RHmn,Enorm,zMold,zRold,zLold, & & JRIT,NRIT,MODEL,N,NG,METHD,NPROB,NMOD,kUNIT,jUNIT,NREC,NATM, & & Nadd,Nsub,IPRT,Jatm,Katm,Latm,MREC,iGRV,massloss ``` I have converted this to… ```auto real, save :: arad3, atmn, change, chgmax, chgmin, crad, cwrk, dflux, dlmn, dlmx, dm(mj), dmat, dmix, dpat, dpmx real, save :: dpmn, dtime, dtmax, dtmin, dtmn, dxmn, dxmx, dzdt, dzmax, dzmin, ener, enorm, factim, grv(mj), rhmn real, save :: rlh, taujk, taux, time, vx(mj, mh), x(mj, mh), xcorm, xh2, xtimod, zflux, zlold, zm(mj), zmass, zmmn real, save :: zmmx, zmold, zrold integer, save :: igrv, iprt, jatm, jrit, junit, katm, kunit, latm, massLoss, methd, model, mrec, n, nadd, natm, ng integer, save :: nmod, nprob, nrec, nrit, nsub ``` I have not done anything with the collective name (`GIC`). Is this correct? ---
**Author:** ![themos](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/themos/32/521_2.png) [@themos](https://fortran-lang.discourse.group/u/themos)\ **Post date:** [October 21, 2021, 8:48am UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/2 "2021-10-21T08:48:08Z")
No. You should create a module, called GIC, and declare all these in the module. You do not need the SAVE attribute in the module, it is implied. You should declare the reals as DOUBLE PRECISION, not REAL. There may be complications if GIC has different definitions in different program units or there are EQUIVALENCE statements. ---
**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:** [October 21, 2021, 11:47am UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/3 "2021-10-21T11:47:29Z")
This paper can be useful: [https://www.cl.cam.ac.uk/~acr31/pubs/orchard-camfort.pdf](https://www.cl.cam.ac.uk/~acr31/pubs/orchard-camfort.pdf) Example “ **Figure 1** ” Common block ```auto program foo integer :: x, y common x, y call bar() end program foo ... ``` Using module ```auto module common integer :: x integer :: y end module common ``` ```auto program foo use common call bar() end program foo ... ``` ---
**Author:** ![msz59](https://avatars.discourse-cdn.com/v4/letter/m/3d9bf3/32.png) [@msz59](https://fortran-lang.discourse.group/u/msz59)\ **Post date:** [October 21, 2021, 12:15pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/4 "2021-10-21T12:15:41Z")
Using `common` as the name for the module in the above example may be misleading, as the program might (and usually did) contain more than one block, named. I would rather follow @themos’ advice and show a slightly modified conversion pattern. Note also, that the `bar` subroutine must `use abc` as well, just as it would have to declare `common /abc/ ...` in the old style. The big advantage of the new style is that the module, defined just once, guarantees the consistency of its variables when used in other places of the program. The old `common` approach makes the programmer responsible for all `common /name/` declarations in any program unit that uses it to be consistent. In old days people used include files to achieve that but AFAIR, the F77 standard did not officially provide such a ‘INCLUDE directive’, it was rather a popular extension. ```auto ! using common program foo integer :: x, y common /abc/ x, y call bar() end program foo ... ! using module module abc integer :: x integer :: y end module abc program foo use abc call bar() end program foo ... ``` ---
**Author:** ![garynewport](https://avatars.discourse-cdn.com/v4/letter/g/898d66/32.png) [@garynewport](https://fortran-lang.discourse.group/u/garynewport)\ **Post date:** [October 21, 2021, 2:01pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/5 "2021-10-21T14:01:53Z")
I should explain that I changed `double precision` to `real`, under the advice I got elsewhere (that makes sense). Not sure we need the precision currently achieved, whilst any reduction in execution time would be incredibly beneficial. Until I run the model I won’t know if this decision is a good one or not (but I can always revert back if needs be). Equally, though `save` is implicit, I took from another post of mine that I should not rely upon that implicit nature and declare the `save` explicitly; hence my addition there. Thank you so much for the information on the module (and naming). I will be sharing shortly my understanding of that and believe I have understood it correctly, but would appreciate any further advice. ---
**Author:** ![garynewport](https://avatars.discourse-cdn.com/v4/letter/g/898d66/32.png) [@garynewport](https://fortran-lang.discourse.group/u/garynewport)\ **Post date:** [October 21, 2021, 2:30pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/6 "2021-10-21T14:30:02Z")
I originally had two files (`parm.h` and `xvar.h`) that were then included throughout two programs I have… `parm.h` ```auto IMPLICIT DOUBLE PRECISION (A-H,O-Z), INTEGER(I-N) PARAMETER (MJ=4000,MH=4,ME=9,MTAU=20000) parameter(SIG=5.67051d-5 , PI=3.14159265359d0) parameter(GRAV=6.6704d-8 , CC=2.99792458d10) parameter(HMASS=1.6732d-24) parameter ( xm_sun = 1.989d33 ) ! Solar Mass (g) parameter ( r_sun = 6.9599d10 ) ! Solar Radius (cm) parameter ( xl_sun = 3.83d33 ) ! Solar Luminosity (erg/s) parameter ( yr = 3.1556736d+7 ) ! yr in sec parameter ( xmdot_sunyr = 6.30268d25 )! acc. Rate in M_sun/yr ``` `xvar.h` ```auto COMMON/ GIC / X(MJ,MH), VX(MJ,MH), GRV(MJ), & & zM(MJ),dM(MJ),Zmass,Zflux,dflux,xTimod,xCorm, & & TIME,DTIME,FACTIM,DTMIN,DTMAX,CHGMIN,CHGMAX,CHANGE, & & dLmx,dLmn,dPmx,dPmn,dXmn,dXmx,dZmax,dZmin,dZdt, & & dMat,Atmn,TAUx,dPat,RLH,Crad,Cwrk,xH2,ener,Arad3,taujk, & & dTmn,dMix,zMmn,zMmx,RHmn,Enorm,zMold,zRold,zLold, & & JRIT,NRIT,MODEL,N,NG,METHD,NPROB,NMOD,kUNIT,jUNIT,NREC,NATM, & & Nadd,Nsub,IPRT,Jatm,Katm,Latm,MREC,iGRV,massloss COMMON/ HY /HA(MH,2*MH+1),HW(MH,MH+1,MJ),HX(MH,MH+1), & & E(MH),G(MH),HC(MH,MH),HD(MH,MH),HE(MH,MH) COMMON/ CORR /DG(MH),SMIN(MH),SMAX(MH),EPS(MH), & & JG(MH),JC(MH),ITMIN,ITMAX,ITER real*8 element(MJ,ME),velement(MJ,ME) real*8 nitrogen,lithium COMMON/helium/hydrogen(MJ),deuterium(MJ),helium3(MJ), & & helium4(MJ),carbon(MJ),nitrogen(MJ),oxygen(MJ), & & lithium(MJ),erest(MJ), & & vhydrogen(MJ),vdeuterium(MJ),vhelium3(MJ), & & vhelium4(MJ),vcarbon(MJ),vnitrogen(MJ),voxygen(MJ), & & vlithium(MJ),verest(MJ) equivalence (element,hydrogen) , (velement,vhydrogen) common/ahycopacity/rhyr(23),thyr(28),auxchyop(23,28) common/ahecopacity/rhel(25),thel(32),auxcheop(25,32) COMMON/MIX/ICONVECT(MJ),ienergy(MJ) character*48 SFILE,OFILE,PFILE,LFILE,FILEZ integer unitz,start_zones,increment_zones,iunit,lunit real*8 radM(10),radR(10) COMMON/ZONES/ SFILE,OFILE,PFILE,LFILE,FILEZ,radM,radR,Nrad, & & unitz,start_zones,increment_zones,iunit,lunit ``` I’m not too sure where the lines between the `COMMON` blocks should go (with the preceeding `common`, subsequent `common` or independently - where they could exist within the `parm.h`) However, given the above advice and following some reading around, I have arrived at this… `modules.h` ```auto module stellar_values implicit none integer, parameter :: mj = 4000 integer, parameter :: mh = 4 integer, parameter :: me = 9 integer, parameter :: MTau = 20000 real, parameter :: sig = 5.67051d-5 real, parameter :: pi = 3.14159265359d0 ! Pi real, parameter :: grav = 6.6704d-8 real, parameter :: cc = 2.99792458d10 real, parameter :: hmass = 1.6732d-24 real, parameter :: xm_sun = 1.989d33 ! Solar mass (g) real, parameter :: r_sun = 6.9599d10 ! Solar radius (cm) real, parameter :: xl_sun = 3.83d33 ! Solar luminosity (erg/s) real, parameter :: yr = 3.1556736d7 ! yr in sec real, parameter :: xmdot_sunyr = 6.30268d25 ! acc. rate in M_sun/yr end module module ahecopacity real, save :: auxcheop(25,32), rhel(25), thel(32) end module module ahycopacity real save :: auxchyop(23,28), rhyr(23), thyr(28) end module module gic real, save :: arad3, atmn, change, chgmax, chgmin, crad, cwrk, dflux, dlmn, dlmx, dm(mj), dmat, dmix, dpat, dpmx real, save :: dpmn, dtime, dtmax, dtmin, dtmn, dxmn, dxmx, dzdt, dzmax, dzmin, ener, enorm, factim, grv(mj), rhmn real, save :: rlh, taujk, taux, time, vx(mj, mh), x(mj, mh), xcorm, xh2, xtimod, zflux, zlold, zm(mj), zmass, zmmn real, save :: zmmx, zmold, zrold integer, save :: igrv, iprt, jatm, jrit, junit, katm, kunit, latm, massLoss, methd, model, mrec, n, nadd, natm, ng integer, save :: nmod, nprob, nrec, nrit, nsub end module module corr real, save :: dg(mh), lithium, nitrogen, radM(10), radR(10), eps(mh), smax(mh), smin(mh) real, save :: element(mj, me), velement(mj, me) integer, save :: itmin, itmax, iter, jc(mh), jg(mh) end module module helium real, save :: carbon(mj), deuterium(mj), erest(mj), helium3(mj), helium4(mj), hydrogen(mj), oxygen(mj) real, save :: vcarbon(mj), vdeuterium(mj), verest(mj), vhelium3(mj), vhelium4(mj), vhydrogen(mj), vlithium(mj) real, save :: vnitrogen(mj), voxygen(mj) integer, save :: lithium(mj), nitrogen(mj) real, pointer, save :: element, velement real, target, save :: hydrogen, vhydrogen element => hydrogen velement => vhydrogen end module module hy real, save :: e(mh), g(mh), ha(mh, 2 * mh + 1), hc(mh, mh), hd(mh, mh), he(mh, mh), hw(mh, mh + 1, mj), hx(mh, mh + 1) end module module mix character(48), save :: filez, lfile, ofile, pfile, sfile integer, save :: iconvect(mj), ienergy(mj) real, save :: radM(10), radR(10) end module module zones real, save :: nrad, radm, radr integer, save :: increment_zones, iunit, lunit, start_zones, unitz end module ``` I intend to include this as per the way `parm.h` and `xvar.h` were included (though I believe someone has stated this is not actually an accepted methodology?), or I can simply place this at the top of each program file and then include the modules as needed. How close am I? 🙂 ---
**Author:** ![themos](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/themos/32/521_2.png) [@themos](https://fortran-lang.discourse.group/u/themos)\ **Post date:** [October 21, 2021, 3:32pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/7 "2021-10-21T15:32:10Z")
The beauty of MODULE is you don’t INCLUDE them as source, you USE them instead. Start with the stellar\_values MODULE, incorporate it into your build system so that it gets built first. Then you can write _USE stellar\_values_ wherever you had _INCLUDE “parm.h”_. You may have to adjust the placing of the USE source line nearer the top of the subroutine. Your other modules are also going to need a _USE stellar\_values_, to pick up the constants MJ etc. The “element =\> hydrogen” is not going to work outside COMMON BLOCKs. You may have to go the opposite way: declare a TARGET element array element(MJ,ME) and declare POINTER variables for each element and associate hydrogen=\>element(:,1), deuterium=\>element(:,2) and so on. ---
**Author:** ![themos](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/themos/32/521_2.png) [@themos](https://fortran-lang.discourse.group/u/themos)\ **Post date:** [October 21, 2021, 3:43pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/8 "2021-10-21T15:43:17Z")
Actually, for now, keep the EQUIVALENCE statements because pointer initialization does not work well in compilers. In a hurry, so this may not be correct, check carefully: ```auto Module stellar_values Implicit None Integer, Parameter :: mj = 4000 Integer, Parameter :: mh = 4 Integer, Parameter :: me = 9 Integer, Parameter :: mtau = 20000 Real, Parameter :: sig = 5.67051D-5 Real, Parameter :: pi = 3.14159265359D0 ! Pi Real, Parameter :: grav = 6.6704D-8 Real, Parameter :: cc = 2.99792458D10 Real, Parameter :: hmass = 1.6732D-24 Real, Parameter :: xm_sun = 1.989D33 ! Solar mass (g) Real, Parameter :: r_sun = 6.9599D10 ! Solar radius (cm) Real, Parameter :: xl_sun = 3.83D33 ! Solar luminosity (erg/s) Real, Parameter :: yr = 3.1556736D7 ! yr in sec Real, Parameter :: xmdot_sunyr = 6.30268D25 ! acc. rate in M_sun/yr End Module Module ahecopacity Real :: auxcheop(25, 32), rhel(25), thel(32) End Module Module ahycopacity Real :: auxchyop(23, 28), rhyr(23), thyr(28) End Module Module gic Use stellar_values, Only: mh, mj Real :: arad3, atmn, change, chgmax, chgmin, crad, cwrk, dflux, dlmn, & dlmx, dm(mj), dmat, dmix, dpat, dpmx Real :: dpmn, dtime, dtmax, dtmin, dtmn, dxmn, dxmx, dzdt, dzmax, dzmin, & ener, enorm, factim, grv(mj), rhmn Real :: rlh, taujk, taux, time, vx(mj, mh), x(mj, mh), xcorm, xh2, & xtimod, zflux, zlold, zm(mj), zmass, zmmn Real :: zmmx, zmold, zrold Integer :: igrv, iprt, jatm, jrit, junit, katm, kunit, latm, massloss, & methd, model, mrec, n, nadd, natm, ng Integer :: nmod, nprob, nrec, nrit, nsub End Module Module corr Use stellar_values, Only: mh, mj, me Real :: dg(mh), radm(10), radr(10), eps(mh), smax(mh), smin(mh) Integer :: itmin, itmax, iter, jc(mh), jg(mh) End Module Module helium Use stellar_values, Only: mj, me Real :: element(mj, me), velement(mj, me) Real :: carbon(mj), deuterium(mj), erest(mj), helium3(mj), helium4(mj), & oxygen(mj), hydrogen(mj) Real :: vcarbon(mj), vdeuterium(mj), verest(mj), vhelium3(mj), & vhelium4(mj), vhydrogen(mj), vlithium(mj) Real :: vnitrogen(mj), voxygen(mj) Equivalence (hydrogen, element(1,1)) Equivalence (deuterium, element(1,2)) Equivalence (helium3, element(1,3)) Equivalence (helium4, element(1,4)) Equivalence (carbon, element(1,5)) Equivalence (nitrogen, element(1,6)) Equivalence (oxygen, element(1,7)) Equivalence (lithium, element(1,8)) Equivalence (erest, element(1,9)) Equivalence (vhydrogen, velement(1,1)) Equivalence (vdeuterium, velement(1,2)) Equivalence (vhelium3, velement(1,3)) Equivalence (vhelium4, velement(1,4)) Equivalence (vcarbon, velement(1,5)) Equivalence (vnitrogen, velement(1,6)) Equivalence (voxygen, velement(1,7)) Equivalence (vlithium, velement(1,8)) Equivalence (verest, velement(1,9)) End Module Module alt_helium Use stellar_values, Only: mj, me Real, Target :: element(mj, me), velement(mj, me) Real, Pointer :: carbon(:) => element(:, 5), deuterium(:) => element(:, & 2), erest(:) => element(:, 9), helium3(:) => element(:, 3), & helium4(:) => element(:, 4), oxygen(:) => element(:, 7), & hydrogen(:) => element(1:mj, 1), nitrogen(:) => element(:, 6), & lithium(:) => element(:, 8) Real, Pointer :: vcarbon(:) => velement(:, 5), & vdeuterium(:) => velement(:, 2), verest(:) => velement(:, 9), & vhelium3(:) => velement(:, 3), vhelium4(:) => velement(:, 4), & voxygen(:) => velement(:, 7), vhydrogen(:) => velement(:, 1), & vnitrogen(:) => velement(:, 6), vlithium(:) => velement(:, 8) End Module Module hy Use stellar_values, Only: mh, mj Real :: e(mh), g(mh), ha(mh, 2*mh+1), hc(mh, mh), hd(mh, mh), & he(mh, mh), hw(mh, mh+1, mj), hx(mh, mh+1) End Module Module mix Use stellar_values, Only: mj Character (48) :: filez, lfile, ofile, pfile, sfile Integer :: iconvect(mj), ienergy(mj) Real :: radm(10), radr(10) End Module Module zones Real :: nrad, radm, radr Integer :: increment_zones, iunit, lunit, start_zones, unitz End Module Program test Use helium Use iso_c_binding hydrogen(1) = 42.0 Print *, size(hydrogen), size (element), hydrogen(1), element(1,1) End Program ``` ---
**Author:** ![msz59](https://avatars.discourse-cdn.com/v4/letter/m/3d9bf3/32.png) [@msz59](https://fortran-lang.discourse.group/u/msz59)\ **Post date:** [October 21, 2021, 4:07pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/9 "2021-10-21T16:07:36Z")
> [@themos](#): > > The beauty of MODULE is you don’t INCLUDE them as source, you USE them instead. that meaning also that you can’t have it defined in a _module.h_ file but _module.f90_ It should be built (compiled) either together with other code or before. If together, place _module.f90_ before other source files in the compilator invocation. Normally it would be put into a Makefile. BTW, greetings from an astronomer. Nice to see Fortran used in our discipline ---
**Author:** ![CRquantum](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/crquantum/32/730_2.png) [@CRquantum](https://fortran-lang.discourse.group/u/CRquantum)\ **Post date:** [October 21, 2021, 4:39pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/10 "2021-10-21T16:39:59Z")
Besides the professional suggestions given. Perhaps another sloppy way is that, you perhaps could rename those variable like GIC\_xxxx, such as ```auto real, save :: GIC_ X(MJ,MH) ``` so that you know what common block those variables are coming from, with the GIC\_ But then you may need to be careful and change the variable names in your function/subroutine correspondingly. ---
**Author:** ![garynewport](https://avatars.discourse-cdn.com/v4/letter/g/898d66/32.png) [@garynewport](https://fortran-lang.discourse.group/u/garynewport)\ **Post date:** [October 23, 2021, 7:13pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/11 "2021-10-23T19:13:24Z")
I can’t do that at present, because I am trying to minimise the changes I make to the original code; altering it step by step. However, this is certainly a good idea for later. ---
**Author:** ![garynewport](https://avatars.discourse-cdn.com/v4/letter/g/898d66/32.png) [@garynewport](https://fortran-lang.discourse.group/u/garynewport)\ **Post date:** [October 23, 2021, 7:16pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/12 "2021-10-23T19:16:56Z")
Ah, so I save the modules into a modules.f90 (for example) and then compile this, along with the others, but compiling it first? I assume that the compiler then recognises that this module exists; I don’t need to reference it within the file of the other program (let’s say, stelcor.f90)? And hello! 🙂 I first encountered Fortran when working on my MSc on the restricted three body problem. I had an example code of the two body, using Runge-Kutta, in Fortran and used this as an aid to create a C++ model of the RTBP. This is a little more complex! 😆 ---
**Author:** ![msz59](https://avatars.discourse-cdn.com/v4/letter/m/3d9bf3/32.png) [@msz59](https://fortran-lang.discourse.group/u/msz59)\ **Post date:** [October 23, 2021, 7:35pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/13 "2021-10-23T19:35:03Z")
> [@garynewport](#): > > I assume that the compiler then recognises that this module exists; I don’t need to reference it within the file of the other program (let’s say, stelcor.f90)? Well, you do need. To use a module in other program segment, be it in the same or a different source file, one has to put ```auto use modulename ``` line in every such segment. From the compiler point of view, it produces `modulename.mod` for every compiled module, plus a typical _object_ file (`*.o` or `*.obj`). The `mod` files are used when compiler encounters `use modulename` line. The object files (with module subprograms etc.) are linked into the executable. ---
**Author:** ![garynewport](https://avatars.discourse-cdn.com/v4/letter/g/898d66/32.png) [@garynewport](https://fortran-lang.discourse.group/u/garynewport)\ **Post date:** [October 23, 2021, 8:05pm UTC](https://fortran-lang.discourse.group/t/converting-common-am-i-correct/2133/14 "2021-10-23T20:05:47Z")
I’m beginning to think that this is a major change of the original code. I did these changes (and others), then hit a complaint about a declaration of corr (ambigious). Equally, if I am declaring each as equivalent, as you declare, will I not need to ensure that this is reflected in the code somewhere? Anyway, I might slow down on this change and check the old code first. See how it works fully, before reassembling it into .f90 Thank you so much for the help.