[Bug c++/13712] New: Executable runs 25% slower than when compiled with INTEL compiler

[Bug c++/13712] New: Executable runs 25% slower than when compiled with INTEL compiler

[william dot crocker at analog dot com]

Keep up the good work BUT
When I compile my (very large number crunching) program
with the INTEL C++ compiler (icc,v7.0) it runs 20 to 30% faster.
On INTEL I use a single compilation pass with no "special" options, just -O3.
With GCC(3.3.2) I tried all sorts of options, but could not get any closer.
I would really like to continue using GCC,
but 25% is hard to pass up.
I used no special options when GCC was built and installed.

Bill

-- 
           Summary: Executable runs 25% slower than when compiled with INTEL
                    compiler
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: william dot crocker at analog dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: ???
  GCC host triplet: DELL, Pentium4, Linux RedHat 7.3
GCC target triplet: ???


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug c++/13712] Executable runs 25% slower than when compiled with INTEL compiler

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-16 22:54 -------
We need a testcase?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
           Keywords|                            |pessimizes-code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug c++/13712] Executable runs 25% slower than when compiled with INTEL compiler

[william dot crocker at analog dot com]

------- Additional Comments From william dot crocker at analog dot com  2004-01-22 19:42 -------
Subject: Re:  Executable runs 25% slower than when compiled with INTEL compiler


> From dberlin@gcc.gnu.org Fri Jan 16 17:54:53 2004
> Date: 16 Jan 2004 22:54:51 -0000
> From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
> To: william.crocker@analog.com
> Subject: [Bug c++/13712] Executable runs 25% slower than when compiled with INTEL compiler
> X-Bugzilla-Reason: Reporter
> X-Spam-Status: No, hits=0.0 required=10.0
> 	tests=none
> 	version=2.60
> X-Spam-Level:  
> X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp)
> X-Scanned-By: MIMEDefang 2.38
> 
> 
> ------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-16 22:54 -------
> We need a testcase?

I can probably put together a test case but I don't think you
are going to like it. (I tried to make a small test case, but it
did not demonstrate the problem.)

My app is 750K LOC.
gprof shows that a single 2K line function accounts
for most (if not all) of the 25% difference in execution speed.
This function is primarily floating point operations
with a little control logic.

I can try to carve this function out
and see if it demonstrates the problem.

Would that be satisfactory ?

Bill

> 
> -- 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |WAITING
>            Keywords|                            |pessimizes-code
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712
> 
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-22 19:45 -------
No we do not care about how bad the code looks, we can always reduce it.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |optimization


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-01-22 19:48 -------
That would be a good first step. The testcase doesn't have to be particularly  
small as a first attempt, but it should be selfcontained. The testcase also  
doesn't have to do something particularly useful.  
  
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[william dot crocker at analog dot com]

------- Additional Comments From william dot crocker at analog dot com  2004-01-29 13:10 -------
Subject: Re:  Executable runs 25% slower than when compiled with INTEL compiler


> From dberlin@gcc.gnu.org Thu Jan 22 14:48:06 2004
> Date: 22 Jan 2004 19:48:04 -0000
> From: "bangerth at dealii dot org" <gcc-bugzilla@gcc.gnu.org>
> To: william.crocker@analog.com
> Subject: [Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler
> X-Bugzilla-Reason: Reporter
> X-Spam-Status: No, hits=0.0 required=10.0
> 	tests=none
> 	version=2.60
> X-Spam-Level:  
> X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp)
> X-Scanned-By: MIMEDefang 2.38
> 
> 
> ------- Additional Comments From bangerth at dealii dot org  2004-01-22 19:48 -------
> That would be a good first step. The testcase doesn't have to be particularly  
> small as a first attempt, but it should be selfcontained. The testcase also  
> doesn't have to do something particularly useful.  
>

I sent in my test case, but the bugzilla data base implies that
you are still "waiting".

Did you get my test case or should I send it again ?

Do you have any email filters which would have rejected
my email ?

Bill
  
> W. 
> 
> -- 
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712
> 
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[falk dot hueffner at student dot uni-tuebingen dot de]

------- Additional Comments From falk dot hueffner at student dot uni-tuebingen dot de  2004-01-29 13:16 -------
Subject: Re:  Executable runs 25% slower than when compiled with INTEL compiler

"william dot crocker at analog dot com" <gcc-bugzilla@gcc.gnu.org> writes:

> I sent in my test case, but the bugzilla data base implies that
> you are still "waiting".
> 
> Did you get my test case or should I send it again ?

I don't see any attachments. Could you try again using the "Create a
New Attachment" link at
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712
?



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[william dot crocker at analog dot com]

------- Additional Comments From william dot crocker at analog dot com  2004-01-29 13:29 -------
Subject: Re:  Executable runs 25% slower than when compiled with INTEL compiler


> From dberlin@gcc.gnu.org Thu Jan 29 08:16:41 2004
> Date: 29 Jan 2004 13:16:35 -0000
> From: "falk dot hueffner at student dot uni-tuebingen dot de" <gcc-bugzilla@gcc.gnu.org>
> To: william.crocker@analog.com
> Subject: [Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler
> X-Bugzilla-Reason: Reporter
> X-Spam-Status: No, hits=0.0 required=10.0
> 	tests=none
> 	version=2.60
> X-Spam-Level:  
> X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp)
> X-Scanned-By: MIMEDefang 2.38
> 
> 
> ------- Additional Comments From falk dot hueffner at student dot uni-tuebingen dot de  2004-01-29 13:16 -------
> Subject: Re:  Executable runs 25% slower than when compiled with INTEL compiler
> 
> "william dot crocker at analog dot com" <gcc-bugzilla@gcc.gnu.org> writes:
> 
> > I sent in my test case, but the bugzilla data base implies that
> > you are still "waiting".
> > 
> > Did you get my test case or should I send it again ?
> 
> I don't see any attachments. Could you try again using the "Create a
> New Attachment" link at
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712
> ?

I just attached a compressed (.Z) tar file.

Bill

> 
> 
> 
> -- 
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712
> 
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[falk at debian dot org]

------- Additional Comments From falk at debian dot org  2004-01-29 16:01 -------
Thanks for the test case. I see it's using FP math heavily. Could you also
try the options -ffast-math and -mfpmath=sse? AFAIK the Intel compiler does
the equivalent of these switches by default so they are needed for a fair
comparison.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
  GCC build triplet|???                         |
   GCC host triplet|DELL, Pentium4, Linux RedHat|
                   |7.3                         |
 GCC target triplet|???                         |i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[william dot crocker at analog dot com]

------- Additional Comments From william dot crocker at analog dot com  2004-01-29 16:27 -------
Subject: Re:  Executable runs 25% slower than when compiled with INTEL compiler

> 
> ------- Additional Comments From falk at debian dot org  2004-01-29 16:01 -------
> Thanks for the test case. I see it's using FP math heavily. Could you also
> try the options -ffast-math and -mfpmath=sse? AFAIK the Intel compiler does
> the equivalent of these switches by default so they are needed for a fair
> comparison.
>

Your email suggest that I sould put something (?) after the sse, but the 
online GCC doc does not show this.

I get this when compiling.

>/home/whc/lintel/gcc/usr_local/bin/g++ -O3 -c -Wno-deprecated -ffast-math -mfpmath=sse y.cc
cc1plus: warning: SSE instruction set disabled, using 387 arithmetics

I also tried -msse and -msse2, but got no better than 30 Seconds.

ANYWAY it runs and I get the following which now shows INTEL with only
a 22% advantage versus the previous 37%.

Bill

###### USING GCC ######

`/home/whc/lintel/gcc/usr_local/bin/g++ -v`
Reading specs from /home/whc/lintel/gcc/usr_local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/specs
Configured with: ./configure --prefix=/home/whc/lintel/gcc/usr_local --exec-prefix=/home/whc/lintel/gcc/usr_local
Thread model: posix
gcc version 3.3.2
/home/whc/lintel/gcc/usr_local/bin/g++ -O3 -c -Wno-deprecated -ffast-math -mfpmath=sse y.cc
cc1plus: warning: SSE instruction set disabled, using 387 arithmetics
ls -ls y.o
  46 -rw-r--r--    1 whc      cad         46676 Jan 29 11:05 y.o
/home/whc/lintel/gcc/usr_local/bin/g++ -O3 -o y y.o
/bin/csh -c "(setenv LD_LIBRARY_PATH /home/whc/lintel/gcc/usr_local/lib; time y)"
X422 = 469.196
30.669u 0.007s 0:31.04 98.7%	0+0k 0+0io 235pf+0w

###### USING ICC ######

/dcad/apps/intel/compiler70/ia32/bin/icc -V -c -O y.cc
Intel(R) C++ Compiler for 32-bit applications, Version 7.1   Build 20030307Z
Copyright (C) 1985-2003 Intel Corporation.  All rights reserved.

Edison Design Group C/C++ Front End, version 3.0 (Mar  8 2003 18:39:53)
Copyright 1988-2002 Edison Design Group, Inc.

ls -ls y.o
 144 -rw-r--r--    1 whc      cad        135824 Jan 29 11:06 y.o
/dcad/apps/intel/compiler70/ia32/bin/icc -o y y.o
/bin/csh -c "(setenv LD_LIBRARY_PATH /dcad/apps/intel/compiler70/ia32/lib; time y)"
X422 = 469.196
23.871u 0.011s 0:24.13 98.9%	0+0k 0+0io 178pf+0w









[whc@juno testcase]$ 


> 
> -- 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>   GCC build triplet|???                         |
>    GCC host triplet|DELL, Pentium4, Linux RedHat|
>                    |7.3                         |
>  GCC target triplet|???                         |i686-pc-linux-gnu
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712
> 
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[falk at debian dot org]

------- Additional Comments From falk at debian dot org  2004-01-29 16:48 -------
I've quickly hacked the test case to compile with a C compiler, to compare
gcc against the DEC compiler. I replaced exp(x) with x*x, since exp() is a
libcall and not under the control of the compiler. Then I get on an 800MHz
ev68:

gcc 3.4: 46.18s (-O3 -ffast-math -mcpu=ev67)
DEC C:   30.02s (-O6 -fast)

So there's also something to gain on other platforms...


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
     Ever Confirmed|                            |1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[william dot crocker at analog dot com]

------- Additional Comments From william dot crocker at analog dot com  2004-02-03 21:34 -------
Subject: Re:  Executable runs 25% slower than when compiled with INTEL compiler

GCC Team:

> 
> ANYWAY it runs and I get the following which now shows INTEL with only
> a 22% advantage versus the previous 37%.
> 

I assume I will not see any changes to GCC to improve this
situation in the immediate future.

I guess I need to change my code to simulate the optimizations
performed by the INTEL compiler and NOT performed by GCC.

Do you have any suggestions (or references to suggestions)
as to what these changes might be so that I can make my program
run faster now.

Bill



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[uros at kss-loka dot si]

------- Additional Comments From uros at kss-loka dot si  2004-02-16 14:55 -------
I have done some experiments with CVS gcc-3.5 [3.5.0 20040216 (experimental)]
and gcc-3.2 [3.2 20020903 (Red Hat Linux 8.0 3.2-7)] on P4 3.2GHz, using various
options.

gcc-3.2: g++ -O3
X422 = 469.196

real    0m35.219s
user    0m35.143s
sys     0m0.061s

gcc-3.2: g++ -march=i686 -O3 -ffast-math
X422 = 469.196

real    0m29.439s
user    0m29.410s
sys     0m0.021s

gcc-3.5: g++ -march=i686 -O3 -ffast-math
X422 = 469.196

real    0m26.380s
user    0m26.287s
sys     0m0.004s

gcc-3.5: g++ -march=i686 -msse2 -mfpmath=sse -O3 -ffast-math
X422 = 469.196

real    0m26.591s
user    0m26.359s
sys     0m0.059s

gcc-3.5: g++ -march=i686 -O3 -ffast-math,
with all functions in source changed to __builtin_<function>:
HUGE_VAL => __builtin_huge_val()
sqrt() => __builtin_sqrt()
log() => __builtin_log()
exp() => __built_in_exp()
X422 = 469.196

real    0m23.145s
user    0m23.115s
sys     0m0.018s


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug rtl-optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[steven at gcc dot gnu dot org]

------- Additional Comments From steven at gcc dot gnu dot org  2005-01-23 18:39 -------
Where are we standing with this one today? 
 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug rtl-optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[uros at kss-loka dot si]

------- Additional Comments From uros at kss-loka dot si  2005-01-24 11:16 -------
(In reply to comment #14)
> Where are we standing with this one today? 

gcc version 4.0.0 20050124 (experimental)

g++ -O3 -ffast-math y.cc
real    0m27.102s
user    0m26.980s
sys     0m0.016s

g++ -O3 -ffast-math -D__NO_MATH_INLINES y.cc
real    0m23.484s
user    0m23.307s
sys     0m0.076s

g++ -O3 -march=pentium4 -ffast-math -D__NO_MATH_INLINES y.cc
real    0m23.101s
user    0m23.014s
sys     0m0.078s

g++ -O3 -march=pentium4 -mfpmath=sse -ffast-math -D__NO_MATH_INLINES y.cc
real    0m31.650s
user    0m31.605s
sys     0m0.025s

g++ -O3 -march=pentium4 -mfpmath=sse -ffast-math y.cc
real    0m29.068s
user    0m28.863s
sys     0m0.023s

g++ -O3 -march=pentium4 -mfpmath=sse y.cc
real    0m35.343s
user    0m34.848s
sys     0m0.047s

g++ -O3 -march=pentium4 -mfpmath=sse -ffast-math -mno-80387 -D__NO_MATH_INLINES y.cc
*** FAILED: X422 = nan ***
real    2m56.700s
user    2m55.615s
sys     0m0.145s

g++ -O3 -march=pentium4 -mfpmath=sse -mno-80387 -D__NO_MATH_INLINES y.cc
*** TIMEOUT AFTER 3min ***

-mfpmath=sse runs a bit slow.
-mno-80387 IMHO generates wrong code.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug rtl-optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[steven at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
   Last reconfirmed|2004-05-30 04:36:06         |2005-04-24 14:18:13
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug rtl-optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[steven at gcc dot gnu dot org]

------- Additional Comments From steven at gcc dot gnu dot org  2005-05-07 15:27 -------
Looks like -D__NO_MATH_INLINES makes gcc produced code much better... 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug rtl-optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[steven at gcc dot gnu dot org]

------- Comment #17 from steven at gcc dot gnu dot org  2006-02-27 14:22 -------
For -D__NO_MATH_INLINES we're probably not going to make any progress as long
as Uli is the glibc maintainer.

Other than that, this appears to be fixed.  Note that ICC has -ffast-math and
SSE as the defaults, where GCC choses for safe math and code that works on any
ix86 CPU, not just the ones with SSE.  So if there is still a significant
difference, it is as much philosophical as it is in code generation.

Given the right set of options, GCC can compete with ICC on my Pentium4 box,
and on Uros' box.  So there doesn't seem to be a good reason to keep this
report open.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |steven at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712

[Bug rtl-optimization/13712] Executable runs 25% slower than when compiled with INTEL compiler

[steven at gcc dot gnu dot org]

------- Comment #18 from steven at gcc dot gnu dot org  2006-02-27 14:22 -------
.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13712