用于点对点的多GPU

Question

我有一些困难，为对等通信设置2个GPU。我正在使用Cuda 4.0，并使用fortran进行编程。PGI编译器

我编写了一个程序，确认我在我的节点上有4个GPU可用。

我决定使用其中的两个，但是有以下错误：0: DEALLOCATE:无效设备指针。

subroutine  directTransfer()

        use cudafor
        implicit none

        integer, parameter :: N = 4*1024*1024
        real, pinned, allocatable :: a(:), b(:)
        real, device, allocatable :: a_d(:), b_d(:)


        !these hold free and total memory before and after
        !allocation, used to verify  allocation happening on proper devices

        integer (int_ptr_kind()),allocatable ::
     &   freeBefore(:), totalBefore(:),
     &   freeAfter(:), totalAfter(:)

        integer :: istat, nDevices, i, accessPeer, timingDev
        type(cudaDeviceProp)::prop
        type(cudaEvent)::startEvent,stopEvent
        real :: time

        !allocate host arrays
        allocate(a(N), b(N))
        allocate(freeBefore(0:nDevices -1),
     &      totalBefore(0:nDevices -1))
        allocate(freeAfter(0:nDevices -1),
     &      totalAfter(0:nDevices -1))
        write(*,*) 'Start!'
        !get devices ionfo (including total and free memory)
        !before allocation
        istat = cudaGetDeviceCount(nDevices)
        if(nDevices < 2) then
            write(*,*) 'Need at least two CUDA capable devices'
            stop
        end if

          write(*,"('Number of CUDA-capable devices: ',
     &       i0, /)"),nDevices

        do i = 0, nDevices - 1
            istat = cudaGetDeviceProperties(prop, i)
            istat = cudaSetDevice(i)
            istat = cudaMemGetInfo(freeBefore(i), totalBefore(i))
        end do

       !is the trouble zone!!
        istat = cudaSetDevice(0)
        allocate(a_d(N))
        istat = cudaSetDevice(1)
        allocate(b_d(N))


       deallocate(freeBefore, totalBefore,freeAfter,totalAfter)
       deallocate(a,b,a_d,b_d)
       end subroutine  directTransfer 

以下是我没有错误的地方：

istat = cudaSetDevice(0)
allocate(a_d(N))
!istat = cudaSetDevice(1)
!allocate(b_d(N))

在此情况下，也没有错误：

!istat = cudaSetDevice(0)
!allocate(a_d(N))
istat = cudaSetDevice(1)
allocate(b_d(N))

但是这个返回错误

istat = cudaSetDevice(0)
allocate(a_d(N))
istat = cudaSetDevice(1)
allocate(b_d(N))

因此，我似乎不能设置2GPU来启动我的程序。你能帮我理解为什么不能设置2GPU和解决这个问题的提示吗？

Answer 1

谢谢JackOLantern！

这就是诀窍。我修改了代码，如下所示，它运行得非常完美

!clean up      
deallocate(freeBefore, totalBefore,freeAfter,totalAfter)
istat = cudaSetDevice(0)
deallocate(a_d)
istat = cudaSetDevice(1)
deallocate(b_d)
deallocate(a,b)

这是我的问题答案。希望它能帮助别人。