Re: 32-bit profiling counts?

[Andrew J. Schorr]

Hi,

On Fri, Jun 05, 2020 at 03:44:10PM +0000, Peter Lindgren wrote:
> I've been profiling a very long-running gawk program, and after some time the 
> counts of the innermost loops roll over to negative numbers. I wonder whether 
> the profile counts are 32-bit signed integers? Could you confirm this? And 
> what do you think about changing them to 64-bit integers?
> 
> This isn't my original program, but one designed just to show this issue:
> 
> 
> 
>         # gawk profile, created Fri Jun  5 09:17:14 2020
> 
> 
>         # BEGIN rule(s)
> 
> 
>         BEGIN {
>      1          two31plus1 = (1024 * 1024 * 1024 * 2) + 1
>      1          status = 1024 * 1024 * 128
> -2147483647     for (x = 1; x <= two31plus1; x++) {
> -2147483647             if (! (x % status)) { # 16
>     16                          print "Status: " x
>                         }
>                 }
>         }

What platform are you running on? From my inspection of the code, it looks like
the counts are stored in an integer of type "long".  In awk.h, I think the
relevant item is `exec_count', which is defined as `d.dl', and d.dl is a long.
On my CentOS Linux x86_64 system, that's a 64-bit signed integer, and here's
what I see when I run this program:

bash-4.2$ cat /tmp/profile.awk 
BEGIN {
        two31plus1 = 2^31+1
        status = 2^27
        for (x = 1; x <= two31plus1; x++) {
                if (! (x % status)) {
                        print "Status: " x
                }
        }
}
bash-4.2$ gawk --profile=myprof.out -f /tmp/profile.awk 
Status: 134217728
Status: 268435456
Status: 402653184
Status: 536870912
Status: 671088640
Status: 805306368
Status: 939524096
Status: 1073741824
Status: 1207959552
Status: 1342177280
Status: 1476395008
Status: 1610612736
Status: 1744830464
Status: 1879048192
Status: 2013265920
Status: 2147483648
bash-4.2$ cat myprof.out 
        # gawk profile, created Sat Jun  6 11:23:18 2020

        # BEGIN rule(s)

        BEGIN {
     1          two31plus1 = (1024 * 1024 * 1024 * 2) + 1
     1          status = 1024 * 1024 * 128
2147483649      for (x = 1; x <= two31plus1; x++) {
2147483649              if (! (x % status)) { # 16
    16                          print "Status: " x
                        }
                }
        }

Regards,
Andy