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From Dmitriy Lyubimov <>
Subject Re: SSVD Parameters Constrains
Date Sun, 07 Oct 2012 21:55:18 GMT
Ahmed, if you are getting this, in all cases people talked about it it
meant their problem was too small.  If A has m x n geometry, then it
must be true that k+p<=min(m,n).

Another possible reason is if height of blocks of A crerated in the
mappers are less than k+p. In practice we yet to see a problem that
actually may ever run into condition (although it is definitely
possible if you occasionally have very dense very large row vectors so
they take up enough space to create split block height problem). If it
is indeed split block height problem, then the remedy is to increase
split size either by hadoop parameter or (i think) one of the SSVD
command line parameters. Although like i said nobody yet ran into
block height deficiency problem yet so i have no knowledge of verified
resolution of this problem by means of manipulating hadoop parameter
setup in Mahout.


On Sun, Oct 7, 2012 at 2:16 PM, Ahmed Elgohary <> wrote:
> Hi,
> Can someone list all the constrains on the parameters (k,p &aBlockRows)
> that should be satisfied in order for the Q-job in ssvd to work fine? I
> tried many values, made sure that (k+p<=m & k+p<=n & p is in the range
> .. 200). but I am still getting the errors: "Givens thin QR: must be true:
> m>=n" or ""new m can't be less than n".
> thanks,
> --ahmed

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