[phobos] [D-Programming-Language/phobos] 3cf671: Add std.parallelism.

Wed Apr 27 14:09:21 PDT 2011

I believe some AMD 64 CPUs allow independent loads to be reordered, which is contrary to the current Intel 64 spec.  Not sure whether this has anything to do with the failure though.

On Apr 26, 2011, at 9:10 PM, Brad Roberts wrote:

> It's a dual core amd:
> 
> vendor_id       : AuthenticAMD
> cpu family      : 15
> model           : 75
> model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
> stepping        : 2
> cpu MHz         : 1000.000
> cache size      : 512 KB
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht
> syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow rep_good extd_apicid pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy
> 
> Actually, showing up on one box but not another is strong evidence of a concurrency bug in my experience.  Different
> cpu's at different speeds, with different speed memory and other side components change timings enough to expose bugs
> that otherwise haven't occurred elsewhere.
> 
> On 4/26/2011 8:44 PM, David Simcha wrote:
>> What about the Linux 64 machine?  I'm getting some weird segfaults in std.parallelism that I can't reproduce on my Linux
>> 64 VM.  I'm currently running the std.parallelism unittests in a loop and they're passing every time.  Furthermore, I've
>> been using std.parallelism for real work on Linux 64 since DMD was capable of producing 64-bit binaries and it's worked
>> fine.  It also passed a Jinx test a few weeks back.  (Jinx is software that's designed to make buggy multithreaded
>> programs fail by fiddling with timings.  Bartosz Milewski tested std.parallelism with it after seeing my blog post.  The
>> point is that this is evidence against the issue being a latent concurrency bug.)  Therefore, I'm thinking something
>> very weird is going on with auto tester.
>> 
>> Also, I noticed it's segfaulting on FreeBSD, too.  I'm installing a FreeBSD VM right now to look into this.
>> 
>> On 4/26/2011 9:38 PM, Brad Roberts wrote:
>>> Good point.. I'll make a note to myself to add system definitions for
>>> those boxes somewhere obvious since that's important for some things.  The
>>> freebsd box is an ancient pos, but it works:
>>> 
>>> CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (2992.52-MHz 686-class CPU)
>>>   Origin = "GenuineIntel"  Id = 0xf41  Family = f  Model = 4  Stepping = 1
>>> 
>>> Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>>> 
>>>   Features2=0x441d<SSE3,DTES64,MON,DS_CPL,CNXT-ID,xTPR>
>>>   TSC: P-state invariant
>>> real memory  = 2147483648 (2048 MB)
>>> avail memory = 2091065344 (1994 MB)
>>> ACPI APIC Table:<A M I  OEMAPIC>
>>> FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
>>> FreeBSD/SMP: 1 package(s) x 1 core(s) x 2 HTT threads
>>>  cpu0 (BSP): APIC ID:  0
>>>  cpu1 (AP/HT): APIC ID:  1
>>> 
>>> 
>>> 
>>> On Tue, 26 Apr 2011, David Simcha wrote:
>>> 
>>>> Date: Tue, 26 Apr 2011 21:02:07 -0400
>>>> From: David Simcha<dsimcha at gmail.com>
>>>> Reply-To: Discuss the phobos library for D<phobos at puremagic.com>
>>>> To: Discuss the phobos library for D<phobos at puremagic.com>
>>>> Subject: Re: [phobos] [D-Programming-Language/phobos] 3cf671: Add
>>>>     std.parallelism.
>>>> 
>>>> I actually realized that FreeBSD matters by looking at the auto tester to make
>>>> sure the checkin wasn't breaking anything on OSX, which I also don't have
>>>> access to.  I have a static assert that will probably fail (fixing it right
>>>> now since it's trivial).  The other issue is that FreeBSD appears broken for
>>>> unrelated reasons right now.  I just pushed a fix based on reading some
>>>> documentation about FreeBSD, but I have no idea whether it's right or not
>>>> because I don't have a FreeBSD box to test it on.  Also, the functionality is
>>>> hard to automatically test because you need to know how many cores the box
>>>> you're running on actually has.
>>>> 
>>>> On 4/26/2011 8:45 PM, Brad Roberts wrote:
>>>>> Assuming you have a good unit test for it, just check the auto tester...
>>>>> Yes, freebsd/32 is supported for d2.
>>>>> 
>>>>> On Tue, 26 Apr 2011, David Simcha wrote:
>>>>> 
>>>>>> Just realized, are we supporting D2 on FreeBSD yet?  If so, I need to fix
>>>>>> std.parallelism to detect the number of CPUs on it.  I think this is the
>>>>>> same
>>>>>> as on OSX, though.  (I used sysctlbyname on OSX.  Someone please confirm
>>>>>> this
>>>>>> is right on BSD.)
>>>>>> 
>>>>>> On 4/26/2011 8:06 PM, noreply at github.com wrote:
>>>>>>> Branch: refs/heads/master
>>>>>>> Home:   https://github.com/D-Programming-Language/phobos
>>>>>>> 
>>>>>>> Commit: 3cf67160b82d87d8de0bc7564aa1474149a92349
>>>>>>>       https://github.com/D-Programming-Language/phobos/commit/3cf67160b82d87d8de0bc7564aa1474149a92349
>>>>>>> Author: dsimcha<dsimcha at gmail.com>
>>>>>>> Date:   2011-04-26 (Tue, 26 Apr 2011)
>>>>>>> 
>>>>>>> Changed paths:
>>>>>>>     M changelog.dd
>>>>>>>     M posix.mak
>>>>>>>     A std/parallelism.d
>>>>>>>     M unittest.d
>>>>>>>     M win32.mak
>>>>>>> 
>>>>>>> Log Message:
>>>>>>> -----------
>>>>>>> Add std.parallelism.
>>>>>>> 
> 
> _______________________________________________
> phobos mailing list
> phobos at puremagic.com
> http://lists.puremagic.com/mailman/listinfo/phobos