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Oracle Solaris Studio 12.2：OpenMP API 用户指南

6.6 检查自动作用域的结果

使用编译器注释可检查自动作用域结果，并确定是否因自动作用域失败而对并行区域进行了序列化。

使用 -g 调试选项编译时，编译器将生成行内注释。可以使用 er_src 命令查看这个生成的注释，如下所示。（er_src 命令作为 Solaris Studio 软件的一部分提供；有关更多信息，请参见 er_src(1) 手册页或《Solaris Studio 性能分析器》手册）。

使用 -xvpara 选项进行编译是一个良好的开端。使用 -xvpara 进行编译可大体确定针对特定构造的自动作用域是否成功。以下是一个示例：

示例 6–1 使用 -vpara 自动确定作用域


%cat source1.f
      INTEGER X(100), Y(100), I, T
C$OMP PARALLEL DO DEFAULT(__AUTO)
      DO I=1, 100
         T = Y(I)
         X(I) = T*T
      END DO
C$OMP END PARALLEL DO
      END
%f95 -xopenmp -xO3 -vpara -c -g source1.f
"source1.f", line 2: Autoscoping for OpenMP construct succeeded. 
Check er_src for details

如果针对特定构造的自动作用域失败，将发出本示例中所示的警告消息（使用 -xvpara）：

示例 6–2 使用 -vpara 自动确定作用域失败


%cat source2.f
      INTEGER X(100), Y(100), I, T
C$OMP PARALLEL DO DEFAULT(__AUTO)
      DO I=1, 100
         T = Y(I)
         CALL FOO(X)
         X(I) = T*T
      END DO
C$OMP END PARALLEL DO
      END
%f95 -xopenmp -xO3 -vpara -c -g source2.f
"source2.f", line 2: Warning: Autoscoping for OpenMP construct failed. 
 Check er-src for details. Parallel region will be executed by
 a single thread.

er_src 所显示的编译器注释中显示了更详细的信息：


% er_src source2.o
Source file: source2.f
Object file: source2.o
Load Object: source2.o




     1.         INTEGER X(100), Y(100), I, T
        
   Source OpenMP region below has tag R1
   Variables autoscoped as SHARED in R1: y
   Variables autoscoped as PRIVATE in R1: t, i
   Variables treated as shared because they cannot be autoscoped in R1: x
   R1 will be executed by a single thread because autoscoping for some variable s was not successful
   Private variables in R1: i, t
   Shared variables in R1: y, x
     2. C$OMP PARALLEL DO DEFAULT(__AUTO)

   Source loop below has tag L1
   L1 parallelized by explicit user directive
   L1 autoparallelized
   L1 parallel loop-body code placed in function _$d1A2.MAIN_ along with 0 inne r loops
   L1 could not be pipelined because it contains calls
     3.         DO I=1, 100
     4.                 T = Y(I)
     5.                 CALL FOO(X)
     6.                 X(I) = T*T
     7.         END DO
     8. C$OMP END PARALLEL DO
     9.         END
    10.