没有使用所需数量的处理器 [英] the desired number of processors are not used

问题描述

我使用openmp并行运行以下fortran代码，但只有一个处理器正在工作。我向代码中添加了一些执行例程，如 OMP_SET_NUM_THREADS 和 OMP_GET_NUM_THREADS ，以遵循并行处理。以下是代码的相关部分：

I am running the following fortran code in parallel using openmp, but only one processor is working. I added some of the execution routines like OMP_SET_NUM_THREADS and OMP_GET_NUM_THREADS to the code to follow the parallel-processing. Here is the relevant part of the code:

integer a,b,omp_get_num_procs,omp_get_max_threads,
& omp_get_num_threads
open( unit=10 , file='threads' , status='new' )
a=4
call omp_set_num_threads(a)
write(10,*) 'num_proc=',omp_get_num_procs()
write(10,*) 'max_threads=',omp_get_max_threads()
write(10,*) 'num_threads=',omp_get_num_threads()

open( unit=7 , file='result' , status='new' )
!$OMP PARALLEL NUM_THREADS(4)
!$OMP DO DEFAULT(PRIVATE) Shared(rho1,rho2,Vnuc)
 do i = 1 , nx
    do j = 1 , ny
      do k = 1 , nz
         b = omp_get_num_threads()
         write(*,*) 'Hello'
         Write(10,*) 'Hello'
         Write(10,*) b
         write(10,100) omp_in_parallel()
100   format(l2)
...
    enddo
  enddo
enddo
!$OMP END DO
!$OMP END PARALLEL

或者在我添加的标题中逐个定义了omp参数

or alternatively to the one by one definition of omp parameters in the header I added

include 'omp_lib.h'

这里是结果：

and here is the result:

 num_proc=           8
 max_threads=           4
 num_threads=           1
 Hello
       1
 T
 Hello
       1
 F
 Hello
       1
 F
 Hello
       1
 F
 Hello
       1
 F

它会继续如此。它正在运行，但只使用一个处理器。任何人都可以帮助我吗？

it continues like that. It is running but using only one processor. Can anyone help me?

推荐答案

Fortran默认使用隐式键入，意味着未声明的变量/函数以（啊，盎司）是真实的。您的解决方案是添加正确类型的运行时例程，如：

Fortran uses implicit typing by default, meaning that undeclared variables/functions starting with (a-h,o-z) are real. Your solution is to either add the correct type of the runtime routines, like:

integer omp_get_num_threads

或者，最好在开始时添加隐式无来停用隐式键入，然后包含头文件：

or, better, add implicit none in the beginning to deactivate implicit typing and then include the header file:

implicit none
include 'omp_lib.h'

编辑：

并行区域外的线程数为1是好的但是，在并行区域中的确应该是4.它可能是混合固定格式和自由格式，前者需要omp指令（例如 C $ OMP ）在行的开始处（在列1上），如下所示：

that the number of threads outside the parallel region is 1 is fine, however, in the parallel region it should indeed be 4. It could be possible that you're mixing fixed and free format, the former requires the omp directive (e.g. C$OMP) at the beginning of a line (on column 1), like so:

      program test
      include 'omp_lib.h'
      write(*,*) 'num_proc =    ',omp_get_num_procs()
      write(*,*) 'max_threads = ',omp_get_max_threads()
      write(*,*) 'num_threads = ',omp_get_num_threads()
C$OMP PARALLEL DO
      do i=1,4
        write(*,*) 'num_threads = ',omp_get_num_threads()
      end do
      end

如果您使用的是自由格式，那么您可以使用！$ OMP 在一行的任何地方。棘手的是，即使在固定格式的源代码中，大多数编译器也允许！注释语句，但是只有当注释开始时，openmp指令才能使用。

If you are using free-form, then you can use !$OMP anywhere on a line. The tricky thing is that most compilers allow ! comment statements even in fixed format source code, but then openmp directives only work when the comment is at the beginning.

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