为了检查内存分配,我们使用单位值填充单精度数组并使用SUM
andDOT_PRODUCT
命令进行查询。这些内在函数在 16777216 (= 2^24) 之后停止计数。我们如何让这些命令来计算数十亿个元素?我们更喜欢避免DO
循环。对于更高精度的阵列,这不是问题。
program allocator
use iso_fortran_env
implicit NONE
integer, parameter :: sp = selected_real_kind ( REAL32 )
integer, parameter :: xlint = selected_int_kind ( INT64 )
integer ( xlint ) :: n = 100000000
real ( sp ), allocatable, dimension ( : ) :: array
integer ( xlint ) :: alloc_status = 0
character ( len = 255 ) :: alloc_msg = ""
! ALLOCATE
allocate ( array ( 1 : n ), stat = alloc_status, errmsg = alloc_msg )
if ( alloc_status /= 0 ) print *, 'allocation error on ', n, ' elements: stat = ', alloc_status, ', errmsg = ', alloc_msg
! POPULATE
array = 1.0_sp
write ( *, '( "number of elements allocated = ", g0 )' ) n
write ( *, '( "sum of elements = ", g0 )' ) sum ( array )
write ( *, '( "dot product = ", g0, / )' ) dot_product ( array, array )
! DEALLOCATE
deallocate ( array, stat = alloc_status, errmsg = alloc_msg )
if ( alloc_status /= 0 ) print *, 'deallocation error on ', n, ' elements: stat = ', alloc_status, ', errmsg = ', alloc_msg
write ( *, '( "compiler version = ", A )' ) compiler_version()
write ( *, '( "compiler options = ", A )' ) trim ( compiler_options() )
end program allocator
输出:
number of elements allocated = 100000000
sum of elements = 16777216.
dot product = 16777216.
compiler version = GCC version 4.6.2 20111019 (prerelease)
compiler options = -fPIC -mmacosx-version-min=10.6.8 -mtune=core2