[Rcpp-devel] trans() changed in latest RcppArmadillo

[baptiste auguie]

After a couple hours switching back and forth between versions, I
found a problem with the scalar product of complex vectors. Here is a
minimal example,

library(inline)
require( RcppArmadillo )
	
## let's calculate this product
c(-1-1i, 1-1i) %*% c(1i, -1i)
 ## 0-2i

## trans() with v0.2.19
fx <- cxxfunction( signature() , '
 arma::cx_colvec A = " (-1,-1)    (+1,-1) ;", B = "(+0,1)  (+0,-1) ;" ;
		arma::cx_colvec res = trans(A) * B;

		return wrap( res ) ;
	', plugin = "RcppArmadillo" )

fx()
## 0-2i

## strans() with v0.2.21
fx <- cxxfunction( signature() , '
 arma::cx_colvec A = " (-1,-1)    (+1,-1) ;", B = "(+0,1)  (+0,-1) ;" ;
		arma::cx_colvec res = strans(A) *B;

		return wrap( res ) ;
	', plugin = "RcppArmadillo" )

fx()
## 1-1i

Best regards,

baptiste



On 31 May 2011 10:01, baptiste auguie <baptiste.auguie at googlemail.com> wrote:
> I was a bit optimistic yesterday; I have not yet been able to produce
> a minimal example but it seems trans/strans was not the end of the
> story in my code. Something else was broken with the change to
> 0.2.21.Thankfully the end results are very visibly wrong.
>
> Best regards,
>
> Baptiste
>
> On 31 May 2011 07:02, Savitsky, Terrance <savitsky at rand.org> wrote:
>> Dr. Sanderson, I've been able to verify that my issue resides in the
>> inv() function (that I typically apply to small p x p matrices, where p
>> = 3 - 10).  In particular, the new version/algorithm induces numerical
>> instability.  I've not yet tested that the results of the inv()
>> computation are generally accurate, only that they are not numerically
>> robust in comparison to 0.2.19.  I'm up against a deadline, so I
>> switched back to 0.2.19, which resolves my problem, for now, but will
>> provide a reproducible example when finished with my work.
>>
>> Terrance
>>
>> -----Original Message-----
>> From: Conrad Sand [mailto:conradsand.rcpp at gmail.com]
>> Sent: Monday, May 30, 2011 6:34 AM
>> To: rcpp-devel at r-forge.wu-wien.ac.at
>> Cc: Savitsky, Terrance
>> Subject: Re: trans() changed in latest RcppArmadillo
>>
>> On 30 May 2011, Terrance Savitsky wrote:
>>> Hello, After upgrading to the 0.2.21 release of RcppArmadillo, my
>>> previously working code (across many functions) ceased working (on a
>>> Windows XP installation).  I re-installed the previous version
>> (0.2.20)
>>> from CRAN (via a server location not yet updated to 0.2.21); didn't
>> fix it.
>>> The timing may be a coincidence, though reading the post on
>>> trans() encourages me to make this post.  While I use 'trans' across
>> my
>>> functions, it is not applied on complex-valued matrices; only
>>> real-valued.  So the prior post wouldn't explain my issue.
>>
>> Hi, I'm the main author of Armadillo.
>>
>> I'm interested in hearing about all regressions -- can you provide
>> more details ?
>>
>> There have been a lot of changes between Armadillo 1.2 and the latest
>> beta (1.99.3).  I'd like to shake out all known bugs before releasing
>> 2.0.
>>
>>
>> Cheers,
>> Conrad
>>
>> --
>> Dr Conrad Sanderson : Sr Research Scientist : NICTA :
>> http://arma.sf.net/cs
>>
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>