Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Nathaniel Smith
On Thu, Feb 16, 2012 at 5:20 PM, Pauli Virtanen wrote: > Hi, > > 16.02.2012 18:00, Nathaniel Smith kirjoitti: > [clip] >> I agree, but the behavior is still surprising -- people reasonably >> expect something like svd to be deterministic. So there's probably a >> doc bug for alerting people that t

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Gael Varoquaux
On Thu, Feb 16, 2012 at 05:00:29PM +, Nathaniel Smith wrote: > I agree, but the behavior is still surprising -- people reasonably > expect something like svd to be deterministic. People are wrong then. Trust me, I work enough with ill-conditionned problems, including SVDs, to know that the alg

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Charles R Harris
On Thu, Feb 16, 2012 at 10:20 AM, Pauli Virtanen wrote: > Hi, > > 16.02.2012 18:00, Nathaniel Smith kirjoitti: > [clip] > > I agree, but the behavior is still surprising -- people reasonably > > expect something like svd to be deterministic. So there's probably a > > doc bug for alerting people t

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Pauli Virtanen
Hi, 16.02.2012 18:00, Nathaniel Smith kirjoitti: [clip] > I agree, but the behavior is still surprising -- people reasonably > expect something like svd to be deterministic. So there's probably a > doc bug for alerting people that their reasonable expectation is, in > fact, wrong :-). The problem

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Charles R Harris
On Thu, Feb 16, 2012 at 10:07 AM, wrote: > On Thu, Feb 16, 2012 at 11:47 AM, wrote: > > On Thu, Feb 16, 2012 at 11:30 AM, wrote: > >> On Thu, Feb 16, 2012 at 11:20 AM, Warren Weckesser > >> wrote: > >>> > >>> > >>> On Thu, Feb 16, 2012 at 10:12 AM, Pierre Haessig < > pierre.haes...@crans.org

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Robert Kern
On Thu, Feb 16, 2012 at 17:07, wrote: > cholesky is also deterministic in my runs We will need to check a variety of builds with different LAPACK libraries and also different matrix sizes to be sure. Alas! -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless e

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread josef . pktd
On Thu, Feb 16, 2012 at 11:47 AM, wrote: > On Thu, Feb 16, 2012 at 11:30 AM,   wrote: >> On Thu, Feb 16, 2012 at 11:20 AM, Warren Weckesser >> wrote: >>> >>> >>> On Thu, Feb 16, 2012 at 10:12 AM, Pierre Haessig >>> wrote: Le 16/02/2012 16:20, josef.p...@gmail.com a écrit : >

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Nathaniel Smith
On Thu, Feb 16, 2012 at 2:08 PM, Pauli Virtanen wrote: > 16.02.2012 14:54, josef.p...@gmail.com kirjoitti: > [clip] >> If I interpret you correctly, this should be a svd ticket, or an svd >> ticket as "duplicate" ? > > I think it should be a multivariate normal ticket. > > "Fixing" SVD is in my op

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread josef . pktd
On Thu, Feb 16, 2012 at 11:30 AM, wrote: > On Thu, Feb 16, 2012 at 11:20 AM, Warren Weckesser > wrote: >> >> >> On Thu, Feb 16, 2012 at 10:12 AM, Pierre Haessig >> wrote: >>> >>> Le 16/02/2012 16:20, josef.p...@gmail.com a écrit : >>> I don't see any way to fix multivariate_normal for this

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread josef . pktd
On Thu, Feb 16, 2012 at 11:20 AM, Warren Weckesser wrote: > > > On Thu, Feb 16, 2012 at 10:12 AM, Pierre Haessig > wrote: >> >> Le 16/02/2012 16:20, josef.p...@gmail.com a écrit : >> >>> I don't see any way to fix multivariate_normal for this case, except >>> for dropping svd or for random pertur

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Robert Kern
On Thu, Feb 16, 2012 at 16:12, Pierre Haessig wrote: > Le 16/02/2012 16:20, josef.p...@gmail.com a écrit : > >> I don't see any way to fix multivariate_normal for this case, except >> for dropping svd or for random perturbing a covariance matrix with >> multiplicity of singular values. > > Hi, > I

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Warren Weckesser
On Thu, Feb 16, 2012 at 10:12 AM, Pierre Haessig wrote: > Le 16/02/2012 16:20, josef.p...@gmail.com a écrit : > > I don't see any way to fix multivariate_normal for this case, except >> for dropping svd or for random perturbing a covariance matrix with >> multiplicity of singular values. >> > Hi,

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Pierre Haessig
Le 16/02/2012 16:20, josef.p...@gmail.com a écrit : I don't see any way to fix multivariate_normal for this case, except for dropping svd or for random perturbing a covariance matrix with multiplicity of singular values. Hi, I just made a quick search in what R guys are doing. It happens there

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread josef . pktd
On Thu, Feb 16, 2012 at 9:08 AM, Pauli Virtanen wrote: > 16.02.2012 14:54, josef.p...@gmail.com kirjoitti: > [clip] >> If I interpret you correctly, this should be a svd ticket, or an svd >> ticket as "duplicate" ? > > I think it should be a multivariate normal ticket. > > "Fixing" SVD is in my op

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Pauli Virtanen
16.02.2012 14:54, josef.p...@gmail.com kirjoitti: [clip] > If I interpret you correctly, this should be a svd ticket, or an svd > ticket as "duplicate" ? I think it should be a multivariate normal ticket. "Fixing" SVD is in my opinion not sensible: its only guarantee is that A = U S V^H down to n

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread josef . pktd
On Thu, Feb 16, 2012 at 8:45 AM, Pauli Virtanen wrote: > 16.02.2012 14:14, josef.p...@gmail.com kirjoitti: > [clip] >> We had other cases of several patterns in quasi-deterministic linalg >> before, but as far as I remember only in the final digits of >> precision, where it didn't matter much exce

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread josef . pktd
On Thu, Feb 16, 2012 at 8:14 AM, wrote: > On Thu, Feb 16, 2012 at 4:44 AM, Pauli Virtanen wrote: >> Hi, >> >> 16.02.2012 06:09, josef.p...@gmail.com kirjoitti: >> [clip] >>> numpy linalg.svd doesn't produce always the same results >>> >>> running this gives two different answers, >>> using scipy

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Pauli Virtanen
16.02.2012 14:14, josef.p...@gmail.com kirjoitti: [clip] > We had other cases of several patterns in quasi-deterministic linalg > before, but as far as I remember only in the final digits of > precision, where it didn't matter much except for reducing test > precision in my cases. > > In the rando

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread josef . pktd
On Thu, Feb 16, 2012 at 4:44 AM, Pauli Virtanen wrote: > Hi, > > 16.02.2012 06:09, josef.p...@gmail.com kirjoitti: > [clip] >> numpy linalg.svd doesn't produce always the same results >> >> running this gives two different answers, >> using scipy.linalg.svd I always get the same answer, which is o

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-16 Thread Pauli Virtanen
Hi, 16.02.2012 06:09, josef.p...@gmail.com kirjoitti: [clip] > numpy linalg.svd doesn't produce always the same results > > running this gives two different answers, > using scipy.linalg.svd I always get the same answer, which is one of > the numpy answers > (numpy random.multivariate_normal is c

Re: [Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-15 Thread josef . pktd
On Wed, Feb 15, 2012 at 10:52 PM, wrote: > Doing a bit of browsing in the numpy tracker, I found this. From my > search this was not discussed on the mailing list. > > http://projects.scipy.org/numpy/ticket/1842 > > The multivariate normal random sample is not always the same, even > though a see

[Numpy-discussion] strange behavior of numpy.random.multivariate_normal, ticket:1842

2012-02-15 Thread josef . pktd
Doing a bit of browsing in the numpy tracker, I found this. From my search this was not discussed on the mailing list. http://projects.scipy.org/numpy/ticket/1842 The multivariate normal random sample is not always the same, even though a seed is specified. It seems to alternate randomly between