CUDA FORTRAN：如果我传递变量而不是数字，函数给出不同的答案 [英] CUDA FORTRAN: function gives different answer if I pass variable instead of number

问题描述

我尝试使用 ISHFT（）函数并行地对一些32位整数进行bithift转换，使用CUDA FORTRAN。

I'm trying to use the ISHFT() function to bitshift some 32-bit integers in parallel, using CUDA FORTRAN.

问题是，我得到不同的答案 ISHFT（-4，-1）和 ISHFT（var，-1），即使 var = -4 。这是我写的测试代码：

The problem is that I get different answers to ISHFT(-4,-1) and ISHFT(var,-1) even though var = -4. This is the test code I've written:

module testshift 

  integer :: test 
  integer, device :: d_test 

contains 

  attributes(global) subroutine testshft () 
    integer :: var
    var = -4
    d_test = ISHFT(var,-1)
  end subroutine testshft

end module testshift

program foo 
  use testshift 

  integer :: i
  call testshft<<<1,1>>>() ! carry out ishft on gpu
  test = d_test            ! copy device result to host
  i = ISHFT(-4,-1)         ! carry out ishft on cpu
  print *, i, test         ! print the results
end program foo

然后编译并执行：

pgf90 testishft.f90 -Mcuda
./a.out 
   2147483646           -2

如果正常工作，两者都应该是2147483646。如果用 4 替换 var ，我得到正确的答案。

Both should be 2147483646 if working correctly. I get the right answer if I replace var with 4.

如何解决这个问题？
感谢您的帮助

How do I fix this problem? Thanks for the help

推荐答案

我找到一个解决方法，发布在此论坛：
http：// www。 pgroup.com/userforum/viewtopic.php?t=2455&postdays=0&postorder=asc&start=15

I've found a workaround, which is posted in this forum: http://www.pgroup.com/userforum/viewtopic.php?t=2455&postdays=0&postorder=asc&start=15

而不是使用ISHFT我使用IBITS，其描述如下： http://gcc.gnu.org/onlinedocs/gfortran/ IBITS.html

Instead of using ISHFT I use IBITS, which is described here: http://gcc.gnu.org/onlinedocs/gfortran/IBITS.html

此外，问题已经在PGI编译器的版本11.3中修复
http://www.pgroup.com/support/release_tprs_2011.htm

Also the problem has since been fixed in version 11.3 of the PGI compiler http://www.pgroup.com/support/release_tprs_2011.htm

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