multidimensional dynamic array allocation for multiblock solver using fortran
I am converting my CFD solver to multiblock solver. I had used dynamic array allocation for the single block solver, but for multiblock, the dynamic array allocation syntax is not clear to me. I tried a sample code, but end up in error "Error: Expression at (1) must be scalar". I also don't know how to pass the multi dimensional allocated array to subroutines. Please, suggest solution, regards
common/iteration/nb integer, dimension (:),allocatable::nib,njb,nkb real, dimension (:,:,:,:),allocatable::x,y,z allocate (nib(nb),njb(nb),nkb(nb)) do l=1,nb ni=nib(l) nj=njb(l) nk=nkb(l) allocate (x(l,ni,nj,nk),y(l,ni,nj,nk),z(l,ni,nj,nk)) enddo call gridatt (x,y,z,nib,njb,nkb) deallocate(x,y,z,nib,njb,nkb) end c subroutine gridatt (x,y,z,nib,njb,nkb) common/iteration/nb integer, dimension (nb)::nib,njb,nkb real, dimension (nb,nib,njb,nkb)::x,y,z return end 
you can not declare an array with variable values for different indexes. thry should be fixed values. i know in this way you waist some amount of memory but there is no way ( as i know). your code should be like this:
common/iteration/nb integer, dimension ( : ),allocatable::nib,njb,nkb real, dimension (:,:,:,: ),allocatable::x,y,z allocate (nib(nb),njb(nb),nkb(nb)) c calculate maximum value of ni, nj and nk in all blocks and store them in MaxNi,MaxNj and MaxNk respectively allocate(x(nb,MaxNi,MaxNj,MaxNk),y(nb,MaxNi,MaxNj, MaxNk),z(nb,MaxNi,MaxNj,MaxNk)) call gridatt (x,y,z,MaxNi,MaxNj,MaxNk) deallocate(x,y,z,nib,njb,nkb) end c subroutine gridatt (x,y,z,MaxNi,MaxNj,MaxNk) common/iteration/nb integer, dimension (nb)::MaxNi,MaxNj,MaxNk real, dimension (nb,MaxNi,MaxNj,MaxNk)::x,y,z return end 
Thank you for your comments.
Well, your suggestion is to use maximum value in i,j,k direction from all blocks. It will work, but sometimes, if the block size varies drastically, this may not be optimum and giving the boundary conditions will be a tough job. 
yes, you are right. but as i know there is no other way. if you want to use the memory efficiently, you should use one array and put the values of different blocks in continuous series. then you can access to any every variables of every block by knowing the size of its previous blocks. i think the following paper can help you in this way. note that the programming of this method is not easy.
Lien, F.S., Chen, W.L. and Leschziner,M.A. (1996). “A Multiblock Implementation of NonOrthogonal Collocated Finite Volume Algorithm for Complex Turbulent Flows”, Int. J. Numer. Methods Fluids, 23, 567588. 
Thank you very much. Regards

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