https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91646
--- Comment #8 from G. Steinmetz <gs...@t-online.de> ---
First a remark, the phrase "the facts" had an unintended
sound, should be read as "the given" or similar.
---
It is apparently not necessary to have a cascade of several
types, a single one suffices. Associated generator :
$ cat generator_type_long.f90
program generator_type_long
implicit none
character(*), parameter :: fmt = '(*(a,i6.6))'
integer :: n ! number of base items
integer :: i
read(*,*) n
n = max (0, min (n, 999999))
print fmt, 'module m'
print fmt, ' type t', 0
do i = 1, n
print fmt, ' real, allocatable :: a', i, '(:)'
end do
print fmt, ' end type'
print fmt, 'end module'
end
The output then looks like :
module m
type t000000
real, allocatable :: a000001(:)
...
real, allocatable :: a004000(:)
end type
end module
Similar to comment 5 a variant with "real, pointer" is placed
next to it, and one with fixed size "real :: a...(10)"
Intentional tested with a very old box, some results :
------- allocatable ------- pointer fixed a(10)
N user time memory user time user time
500 3.1 sec 130 MB 0.026 sec 0.031 sec
1000 7.8 sec 250 MB 0.046 sec 0.045 sec
2000 20.3 sec 540 MB 0.087 sec 0.091 sec
3000 42.2 sec 850 MB 0.125 sec 0.145 sec
4000 68.5 sec 1090 MB 0.180 sec 0.213 sec
For this limited range, memory consumption is roughly ~ N.
OTOH, run time raises from N=1000 to 4000 by a factor of 9.
For higher numbers not necessarily monotone.
Memory consumption goes up stepwise, e.g. for N=4000
between 26 and 58 sec consumption is constant 510 MB,
then doubles between 59 and 63 sec to 1040 MB.
In general depending on size/speed of caches/ram/disc and other.
For slightly different numbers N and N+1, output and dumps can
be diff compared, but not done here.
Numbers vary for different OS, CPU, compiler versions, etc.
