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-rw-r--r--gcc-4.8/gcc/fortran/intrinsic.texi48
1 files changed, 26 insertions, 22 deletions
diff --git a/gcc-4.8/gcc/fortran/intrinsic.texi b/gcc-4.8/gcc/fortran/intrinsic.texi
index 390750186..91adb400e 100644
--- a/gcc-4.8/gcc/fortran/intrinsic.texi
+++ b/gcc-4.8/gcc/fortran/intrinsic.texi
@@ -10207,10 +10207,11 @@ the @var{SIZE} argument.
@item @emph{Example}:
@smallexample
subroutine init_random_seed()
+ use iso_fortran_env, only: int64
implicit none
integer, allocatable :: seed(:)
- integer :: i, n, un, istat, dt(8), pid, t(2), s
- integer(8) :: count, tms
+ integer :: i, n, un, istat, dt(8), pid
+ integer(int64) :: t
call random_seed(size = n)
allocate(seed(n))
@@ -10224,34 +10225,37 @@ subroutine init_random_seed()
! Fallback to XOR:ing the current time and pid. The PID is
! useful in case one launches multiple instances of the same
! program in parallel.
- call system_clock(count)
- if (count /= 0) then
- t = transfer(count, t)
- else
+ call system_clock(t)
+ if (t == 0) then
call date_and_time(values=dt)
- tms = (dt(1) - 1970) * 365_8 * 24 * 60 * 60 * 1000 &
- + dt(2) * 31_8 * 24 * 60 * 60 * 1000 &
- + dt(3) * 24 * 60 * 60 * 60 * 1000 &
+ t = (dt(1) - 1970) * 365_int64 * 24 * 60 * 60 * 1000 &
+ + dt(2) * 31_int64 * 24 * 60 * 60 * 1000 &
+ + dt(3) * 24_int64 * 60 * 60 * 1000 &
+ dt(5) * 60 * 60 * 1000 &
+ dt(6) * 60 * 1000 + dt(7) * 1000 &
+ dt(8)
- t = transfer(tms, t)
end if
- s = ieor(t(1), t(2))
- pid = getpid() + 1099279 ! Add a prime
- s = ieor(s, pid)
- if (n >= 3) then
- seed(1) = t(1) + 36269
- seed(2) = t(2) + 72551
- seed(3) = pid
- if (n > 3) then
- seed(4:) = s + 37 * (/ (i, i = 0, n - 4) /)
+ pid = getpid()
+ t = ieor(t, int(pid, kind(t)))
+ do i = 1, n
+ seed(i) = lcg(t)
+ end do
end if
+ call random_seed(put=seed)
+contains
+ ! This simple PRNG might not be good enough for real work, but is
+ ! sufficient for seeding a better PRNG.
+ function lcg(s)
+ integer :: lcg
+ integer(int64) :: s
+ if (s == 0) then
+ s = 104729
else
- seed = s + 37 * (/ (i, i = 0, n - 1 ) /)
+ s = mod(s, 4294967296_int64)
end if
- end if
- call random_seed(put=seed)
+ s = mod(s * 279470273_int64, 4294967291_int64)
+ lcg = int(mod(s, int(huge(0), int64)), kind(0))
+ end function lcg
end subroutine init_random_seed
@end smallexample