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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Performance of signed vs unsigned types |
| Date | 2011-04-20 12:09 -0700 |
| Organization | None to speak of |
| Message-ID | <ln1v0w68ov.fsf@nuthaus.mib.org> (permalink) |
| References | (2 earlier) <alpine.LFD.2.02.1104201524110.22103@bowman> <3424a29f-facc-4605-bc3d-b6b9d6c22366@r4g2000prm.googlegroups.com> <alpine.LFD.2.02.1104201619090.22217@bowman> <alpine.LFD.2.02.1104201705550.22217@bowman> <alpine.LFD.2.02.1104201718400.22217@bowman> |
Thomas Scrace <tom@scrace.org> writes:
> On Wed, 20 Apr 2011, Thomas Scrace wrote:
>> By comparison, with an unsigned long it took just a few seconds to
>> max out at 9223372036854775807.
>
> Sorry, I meant 18446744073709551615.
(That's 2**64-1.)
That's implausible; there must be something else going on.
If your computer can increment a 64-bit long in 1 nanosecond
(1 GHz), it would take it over 500 years to iterate from 0
to 18446744073709551615. You can tweak the numbers slightly
(maybe your computer is faster than that, maybe it can do multiple
increments per clock cycle, etc.), but not enough to reduce the
time to a few seconds.
You said you added a print statement to the loop, and it took about
a minute to count to 4 million. (BTW, this would be a lot easier if
you had kept that context in your followup.) The print statement is
going to take orders of magnitude longer than a simple increment;
a minute to generate 4 million lines of output is plausible.
The overhead of formatting the output string is going to be
substantial, and even that is likely to be swamped by the time it
takes to physically generate the output.
My best guess is that you're actually iterating over a 32-bit range.
That takes about 6 seconds on my system (with no ouput in the loop).
(A sufficiently clever compiler might also optimize away the loop,
but then it would take no perceptible time, not "just a few seconds".)
Post the code (with no print stastements in the loop) that
"took just a few seconds". Please post the complete compilable
and runnable program. Before the loop starts, have it print the
relevent values from your <limits.h>, e.g.:
#include <limits.h>
...
printf("INT_MAX = %d\n", INT_MAX);
printf("UINT_MAX = %u\n", UINT_MAX);
printf("LONG_MAX = %ld\n", LONG_MAX);
printf("ULONG_MAX = %lu\n", ULONG_MAX);
If this doesn't solve the mystery, we might consider looking at the
generated assembly code, but we're not there yet.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
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Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-20 14:21 +0100
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-20 09:49 -0400
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-20 15:21 +0100
Re: Performance of signed vs unsigned types Peter Nilsson <airia@acay.com.au> - 2011-04-20 15:34 -0700
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-21 17:57 +0100
Re: Performance of signed vs unsigned types Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-04-21 19:26 +0100
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-20 21:45 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-21 06:20 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-21 13:54 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-21 18:50 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-21 16:16 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-21 19:27 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-21 17:24 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-21 21:00 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-21 21:33 -0700
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-22 08:22 +0100
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-22 14:25 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-22 09:21 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-22 14:22 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-22 17:58 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-22 17:33 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-23 09:01 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-23 14:07 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-23 18:14 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 11:42 -0700
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-25 22:34 -0400
Re: Performance of signed vs unsigned types gordonb.nw63u@burditt.org (Gordon Burditt) - 2011-04-26 10:59 -0500
Re: Performance of signed vs unsigned types "madamemandm@yahoo.com" <madamemandm@yahoo.com> - 2011-04-22 07:55 -0700
Re: Performance of signed vs unsigned types Noob <root@127.0.0.1> - 2011-04-22 17:03 +0200
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-22 08:42 -0700
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-22 14:15 -0700
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-22 15:23 -0700
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-22 17:37 -0700
Re: Performance of signed vs unsigned types Seebs <usenet-nospam@seebs.net> - 2011-04-23 02:46 +0000
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-23 14:04 -0700
Re: Performance of signed vs unsigned types Barry Schwarz <schwarzb@dqel.com> - 2011-04-23 14:28 -0700
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 11:43 -0700
Re: Performance of signed vs unsigned types Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-04-23 23:38 +0100
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 11:46 -0700
Re: Performance of signed vs unsigned types Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-04-25 22:43 +0100
Re: Performance of signed vs unsigned types Seebs <usenet-nospam@seebs.net> - 2011-04-24 11:34 +0000
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 11:47 -0700
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-25 12:32 -0700
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 20:25 -0700
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-26 07:45 -0700
Re: Performance of signed vs unsigned types lawrence.jones@siemens.com - 2011-04-24 23:50 -0400
Re: Performance of signed vs unsigned types Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-04-25 02:13 -0700
Re: Performance of signed vs unsigned types Ian Collins <ian-news@hotmail.com> - 2011-04-25 21:36 +1200
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 11:48 -0700
Re: Performance of signed vs unsigned types lawrence.jones@siemens.com - 2011-04-25 16:32 -0400
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-25 15:22 -0700
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 20:32 -0700
Re: Performance of signed vs unsigned types "io_x" <a@b.c.invalid> - 2011-04-26 09:42 +0200
Re: Performance of signed vs unsigned types Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-04-26 12:04 +0100
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-26 08:15 -0700
Re: Performance of signed vs unsigned types Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-04-26 08:35 -0700
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-26 08:52 -0700
Re: Performance of signed vs unsigned types Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-04-26 09:15 -0700
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-26 10:22 -0700
Re: Performance of signed vs unsigned types gordonb.s68qo@burditt.org (Gordon Burditt) - 2011-04-26 19:59 -0500
Re: Performance of signed vs unsigned types "madamemandm@yahoo.com" <madamemandm@yahoo.com> - 2011-04-27 14:15 -0700
Re: Performance of signed vs unsigned types "io_x" <a@b.c.invalid> - 2011-04-28 12:15 +0200
Re: Performance of signed vs unsigned types Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-04-28 03:26 -0700
Re: Performance of signed vs unsigned types Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-04-28 12:09 +0100
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-28 08:03 -0400
Re: Performance of signed vs unsigned types Seebs <usenet-nospam@seebs.net> - 2011-04-28 16:44 +0000
Re: Performance of signed vs unsigned types Gordon Burditt <gordon@hammy.burditt.org> - 2011-04-29 05:42 -0500
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 20:27 -0700
Re: Performance of signed vs unsigned types Ian Collins <ian-news@hotmail.com> - 2011-04-26 15:30 +1200
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-26 00:14 -0700
Re: Performance of signed vs unsigned types Ian Collins <ian-news@hotmail.com> - 2011-04-26 20:23 +1200
Re: Performance of signed vs unsigned types Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-04-26 04:17 -0700
Re: Performance of signed vs unsigned types Ike Naar <ike@sverige.freeshell.org> - 2011-04-22 06:46 +0000
Re: Performance of signed vs unsigned types James Kuyper <jameskuyper@verizon.net> - 2011-04-22 09:37 -0400
Re: Performance of signed vs unsigned types Michael Press <rubrum@pacbell.net> - 2011-04-25 11:49 -0700
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-22 09:09 -0700
Re: Performance of signed vs unsigned types "madamemandm@yahoo.com" <madamemandm@yahoo.com> - 2011-04-22 09:46 -0700
Re: Performance of signed vs unsigned types Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-04-22 20:21 +0100
Re: Performance of signed vs unsigned types "Scott Fluhrer" <sfluhrer@ix.netcom.com> - 2011-04-20 10:06 -0400
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-20 15:28 +0100
Re: Performance of signed vs unsigned types Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-04-20 16:11 +0100
Re: Performance of signed vs unsigned types Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-04-20 08:14 -0700
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-20 16:24 +0100
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-20 17:09 +0100
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-20 17:19 +0100
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-20 12:09 -0700
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-20 21:39 +0100
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-20 15:01 -0700
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-21 11:16 +0100
Re: Performance of signed vs unsigned types "Scott Fluhrer" <sfluhrer@ix.netcom.com> - 2011-04-20 13:06 -0400
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-20 18:16 +0100
Re: Performance of signed vs unsigned types gordonb.bfd7y@burditt.org (Gordon Burditt) - 2011-04-21 11:22 -0500
Re: Performance of signed vs unsigned types Thomas Scrace <tom@scrace.org> - 2011-04-21 19:27 +0100
Re: Performance of signed vs unsigned types Keith Thompson <kst-u@mib.org> - 2011-04-21 12:09 -0700
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