segfault和-fopenmp一个简单的程序 [英] segfault with -fopenmp for a trivial program

问题描述

我正在刷新openmp，并陷入了这个奇怪的境地。剃掉了一堆，我创建了这个最小的小案例，显示问题

b integer，parameter :: n = 10000000
integer :: i
real :: x（n）

do i = 1，n
x（i）= 0.0d0
enddo

结束程序

不指定标志，gfortran 4.3.4在mac（10.6）上编译，程序正确执行。然而，如果我使用-fopenmp启用openmp，程序将终止并出现分段错误。显然，没有代码被执行，因为它立即崩溃。正如您所看到的，openmp在代码中不会用于并行化任何事情。我尝试修改堆栈大小，都使用ulimit -fmax-stack-var-size，并且无论如何，千万个实数不是我定义的一个大数组。

我做错了什么？

解决方案

是的，openmp通常会改变内存的分配方式。以前的讨论： Fortran中的OpenMP

<在网上搜索，我发现 http://homepage.mac.com/eric.c/hpc/contents/documentation/How%20to%20increase%20the%20stack%20size%20on%20Mac%20OS ％20X.pdf

gfortran-mp-4.3 -fopenmp ex2.f90 -Wl，-stack_size，0x40000000，-stack_addr，0xf0000000 -o ex2.exe

解决了我Mac上的问题。

I am refreshing openmp a bit, and got into this weird situation. Shaved off the bunch, I created this minimal trivial case that shows the issue

program ex2
    implicit none
    integer, parameter :: n=10000000
    integer :: i
    real :: x(n)

    do i=1,n
        x(i) = 0.0d0
    enddo

end program

with no flags specified, gfortran 4.3.4 on the mac (10.6) compiles, and the program executes correctly.

However, if I enable openmp with -fopenmp, the program terminates with segmentation fault. No code get executed, apparently, as it crashes immediately. As you see, openmp is never used in the code to parallelize anything. I tried to modify the stack size, both with ulimit the -fmax-stack-var-size, and in any case, ten millions reals is not what I define a big array.

What am I doing wrong ?

解决方案

Yes, openmp typically changes how memory is allocated. A previous discussion: OpenMP in Fortran

Searching on the web, I found http://homepage.mac.com/eric.c/hpc/contents/documentation/How%20to%20increase%20the%20stack%20size%20on%20Mac%20OS%20X.pdf

gfortran-mp-4.3 -fopenmp ex2.f90 -Wl,-stack_size,0x40000000,-stack_addr,0xf0000000 -o ex2.exe

fixed the problem on my Mac.

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