Advice on OpenMP code please

I am seeking advice about some OpenMP code I have written. (THis is my first foray into OpenMP programming.) I would like to know if (a) It is legal code (It currently compiles and gives the expected answers) and (b) If my handling of the 4 threads is optimal.

I have a data array define as

real, allocatable :: d(:,:)

in a module; then created as:

allocate d(d(n,n)) later, and actually used as an array of length len x len

As it happens, the most time consuming part of the calculation can be run as 4 parallel threads which take identical times (to within a few ms) and use the same amount of memory. Each thread produces just 3 integers as its final result and these are stored in an array howmany(15). (The first 3 elements of howmany() hold other data.) I have written the following code to handle this situation for computers with >=4 , 3, 2 and 1 core(s).

! Allow program to modify the number of threads              

	      call omp_set_dynamic(.true.)

	! How many cores to use?     

	      i = omp_get_max_threads()

	      NumThreads = min0(4, i)

	        if(len <= 50) NumThreads = 1 ! <= 50 not worth the overheads

	      call omp_set_num_threads(NumThreads)

	    ! Now the parallel code

	      if(NumThreads == 1) then

	      ! No multicore processor available, so 1 thread at a time.

	      call count_clusters_OMP(1,d,n,len,lower,upper, .true.,NumThreads,ierr)

	      call count_clusters_OMP(2,d,n,len,lower,upper, .true.,NumThreads,ierr)

	      call count_clusters_OMP(3,d,n,len,lower,upper, .true.,NumThreads,ierr)

	      call count_clusters_OMP(4,d,n,len,lower,upper, .true.,NumThreads,ierr)    

	      ! 2 cores

	      else if(NumThreads == 2 .or. NumThreads == 3) then

	      ! 1st 2 calculations

	      !$OMP PARALLEL SECTIONS COPYIN(d, howmany, maxval, minval, n, len)

	      !$OMP SECTION

	      call count_clusters_OMP(1,d,n,len,lower,upper,.true.,NumThreads,ierr)

	      !$OMP SECTION

	      call count_clusters_OMP(2,d,n,len,lower,upper,.false.,NumThreads,ierr)

	      !$OMP END PARALLEL SECTIONS

	      ! Second set

	      !$OMP PARALLEL SECTIONS COPYIN(d, howmany, maxval, minval, n, len)      

	      !$OMP SECTION

	      call count_clusters_OMP(3,d,n,len,lower,upper,.true.,NumThreads,ierr)

	      !$OMP SECTION

	      call count_clusters_OMP(4,d,n,len,lower,upper,.false.,NumThreads,ierr)

	      !$OMP END PARALLEL SECTIONS     

	      ! 4 cores (or more)

	      else if(NumThreads == 4) then

	      !$OMP PARALLEL SECTIONS COPYIN(d, howmany, maxval, minval, n, len)

	      !$OMP SECTION  

	      call count_clusters_OMP(1,d,n,len,lower,upper,.true.,NumThreads,ierr)  

	      !$OMP SECTION

	      call count_clusters_OMP(2,d,n,len,lower,upper,.false.,NumThreads,ierr)

	      !$OMP SECTION

	      call count_clusters_OMP(3,d,n,len,lower,upper,.false.,NumThreads,ierr)

	      !$OMP SECTION

	      call count_clusters_OMP(4,d,n,len,lower,upper,.false.,NumThreads,ierr)

	      !$OMP END PARALLEL SECTIONS

	      endif

(lower, upper, minval and maxval are scalars.)

A colleague of mine has criticised this code on 2 grounds:

1. It is not legal Fortran.
2. I should not manage the threads as I do but let the software do this.

Can I solicit an expert opinion please?

With thanks

Chris G