Translations:OpenACC Tutorial - Adding directives/4/en

OpenACC directives

OpenACC directives are much like OpenMP directives. They take the form of pragma statements in C/C++, and comments in Fortran. There are several advantages to using directives:

• First, since it involves very minor modifications to the code, changes can be done incrementally, one pragma at a time. This is especially useful for debugging purpose, since making a single change at a time allows one to quickly identify which change created a bug.
• Second, OpenACC support can be disabled at compile time. When OpenACC support is disabled, the pragma are considered comments, and ignored by the compiler. This means that a single source code can be used to compile both an accelerated version and a normal version.
• Third, since all of the offloading work is done by the compiler, the same code can be compiled for various accelerator types: GPUs or SIMD instructions on CPUs. It also means that a new generation of devices only requires one to update the compiler, not to change the code.