Hi Wolfgang,
ok, good point. Let's replace the "math loop" with:
for (i=1; i<=1000000000; ++i) {
foo = foo*1.1;
foo = foo/1.1;
foo = pow(foo,1.0);
}
printf("foo=%f\n",foo);
Will this get your system to an almost stand-still?
-Stefan
On Nov 3, 2009, at 22:52, Wolfgang Denk wrote:
> Dear Stefan Schaal,
>
> In message <[email protected]> you wrote:
>> Sorry, I attached the wrong C-program in the previous posting ....
>> here is the corrected version:
>
> I'm not sure what exactly you are trying to test, but I think you
> should invest a little more time in your test cases.
>
>> attached is a little C program that spawns off a task which runs a
>> heavy tiny math job. Despite my 8 processor machine, taking this one
>
> Does it? Not for me.
>
>> void
>> run_task(void *dummy)
>> {
>> int i;
>> double foo = 1.0;
>>
>> for (i=1; i<=100000000; ++i)
>> foo = foo*1.1;
>>
>> return;
>> }
>
> On x86, this code compiles for me into this:
>
> .text
> .p2align 4,,15
> .globl run_task
> .type run_task, @function
> run_task:
> pushl %ebp
> movl %esp, %ebp
> popl %ebp
> ret
> .size run_task, .-run_task
> .ident "GCC: (GNU) 4.4.1 20090725 (Red Hat 4.4.1-2)"
> .section .note.GNU-stack,"",@progbits
>
> Similar on ARM and Power.
>
> As you can see, the compiler completely optimizes away your "tiny math
> job". So what should be loading your CPU?
>
> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: [email protected]
> "Nature is very un-American. Nature never hurries."
> - William George Jordan
>
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