[Rd] R-3.0.1 - "transient" make check failure in splines-EX.r

[Mike Marchywka]

----------------------------------------
> From: Avraham.Adler at guycarp.com
> To: r-devel at r-project.org
> Date: Thu, 30 May 2013 16:17:36 -0500
> Subject: Re: [Rd] R-3.0.1 - "transient" make check failure in splines-EX.r
>
> I just found this thread on StackOverflow <http://stackoverflow.com/questions/13871818/ns-varies-for-no-apparent-reason/13878936> which had the same problem with the `ns` call changing with Revolution, and the answer given by tech support was that the MKL BLAS sometime returns ever-so-slightly different floating point results than a reference BLAS. The problem with that answer is that if it is true, the runs should not change *on the same machine* but it is another example of this issue. Unfortunately, it seems to dead-end too.
>

Read some of the documents on the Intel site about floating point consistency and compiler optimizations. There are 
some reasons that you could get a different result from repeated runs on the same machine. One of these would
be bugs like unititialized memory but another would be things like state of FPU and issues with
multi-threaded code having some order dependencies etc.  

( hotmail can not believe I am trying to post text but maybe you can figure it out from whatver this link eds up looking like.... ) 
 href="http://www.google.com/search?biw=1253&bih=542&hl=en&q=floating+point+low+bits+vary+fpu+prior+state+site%253Aintel.com&oq=floating+point+low+bits+vary+fpu+prior+state+site%253Aintel.com"




> Avraham
>
>
> -----Original Message-----
> From: Adler, Avraham
> Sent: Thursday, May 30, 2013 3:12 PM
> To: Paul Gilbert
> Cc: r-devel at r-project.org
> Subject: RE: R-3.0.1 - "transient" make check failure in splines-EX.r
>
> Thank you very much, Paul.
>
> Serendipitously, I seem to have stumbled on a solution. In my parallel (still unsuccessful) attempt to build a BLAS for a 64bit machine (see <https://stat.ethz.ch/pipermail/r-devel/2013-May/066731.html>) I remembered from ATLAS that under the newer Windows there is a divergence from the "standard" ABI (see <http://math-atlas.sourceforge.net/atlas_install/node57.html>).
>
> Looking through the various makefiles under OpenBLAS, I found the following:
>
> ifeq ($(C_COMPILER), GCC)
> #Test for supporting MS_ABI
> GCCVERSIONGTEQ4 := $(shell expr `$(CC) -dumpversion | cut -f1 -d.` \>= 4)
> GCCVERSIONGT4 := $(shell expr `$(CC) -dumpversion | cut -f1 -d.` \> 4)
> GCCMINORVERSIONGTEQ7 := $(shell expr `$(CC) -dumpversion | cut -f2 -d.` \>= 7)
> ifeq ($(GCCVERSIONGT4), 1)
> # GCC Majar version> 4
> # It is compatible with MSVC ABI.
> CCOMMON_OPT += -DMS_ABI
> endif
>
> I had been building OPBL using gcc4.8.0, which is ostensibly "compatible" with the newer ABI, but Rtools still lives in 4.6.3, which isn't. Recompiling the BLAS with MinGW32 for 4.6.3 created a file that has passed `make check-all` twice now. I plan on comparing the speed with the ATLAS-based blas, and if it is faster, I hope to e-mail the dll and check results to Dr. Ligges.
>
> I say "stumbled serendipitously" because when using the 64 bit version of MinGw 4.6.3 resulted in the same `optim`-based error in `factanal` which I describe in the thread linked-to above. I will try using different versions of MinGW or even trying under Cygwin, I guess.
>
> In any event, Paul, I am curious if when you were trying to compile and had the same issue, were you using a different version or generation of gcc in the BLAS compilation than in the R compilation?
>
> Once again, thank you very much.
>
> Avraham Adler
>
>
> -----Original Message-----
> From: Paul Gilbert
> Sent: Thursday, May 30, 2013 12:26 AM
> To: Adler, Avraham
> Subject: Re: R-3.0.1 - "transient" make check failure in splines-EX.r
>
> Avraham
>
> I resolved this only by switching to a different BLAS on the 32 bit machine.Since no one else seemed to be having problems, I considered it possible that there was a hardware issue on my old 32 bit machine. The R check test failed somewhat randomly, but often. most disconcertingly, it failed because it gives different answers. If you source the code in an R session a few times you have no trouble reproducing this. It gives the impression of an improperly zeroed matrix.
>
> (All this from memory, I'm on the road.)
>
> Paul
>
> On 13-05-28 06:36 PM, Adler, Avraham wrote:
>>
>> Hello.
>>
>> I seem to be having the same problem that Paul had in the thread titled "[Rd] R 2.15.2 make check failure on 32-bit --with-blas="-lgoto2"" from October of last year <https://stat.ethz.ch/pipermail/r-devel/2012-October/065103.html> Unfortunately, that thread ended without an answer to his last question.
>>
>> Briefly, I am trying to compile an Rblas for Windows NT 32bit using OpenBlas (successor to GotoBlas) (Nehalem - corei7), and the compiled version passes all tests except for the "splines-Ex" test in the exact same place that Paul had issues:
>>
>> ~~~~
>>> stopifnot(identical(ns(x), ns(x, df = 1)),
>> + identical(ns(x, df = 2), ns(x, df = 2, knots = NULL)), # not true till 2.15.2
>> + !is.null(kk <- attr(ns(x), "knots")), # not true till 1.5.1
>> + length(kk) == 0)
>> Error: identical(ns(x, df = 2), ns(x, df = 2, knots = NULL)) is not
>> TRUE ~~~~
>>
>> Yet, opening up R and running the actual code shows that the error is transient:
>>
>> ~~~~
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] TRUE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] TRUE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] TRUE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] FALSE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] TRUE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] TRUE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] TRUE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] TRUE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] TRUE
>>> identical(ns(x, df = 2), ns(x, df = 2, knots = NULL))
>> [1] FALSE
>> ~~~~
>>
>> This is the only error I have on the 32-bit version, I believe (trying to build a blas for 64-bit on SandyBridge is a completely different kettle of fish that is causing me to pull out what little hair I have left), and if it can be solved that would be great.
>>
>> Thank you,
>>
>> Avraham
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