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From Ivan Novick <inov...@pivotal.io>
Subject Re: Multiplying a large sparse matrix by a vector
Date Wed, 03 Jan 2018 22:38:04 GMT
Hi Anthony, this does NOT look like a Ubuntu problem, and in fact there is
OSS Greenplum officially on Ubuntu you can see here:
http://greenplum.org/install-greenplum-oss-on-ubuntu/

Greenplum and PostgreSQL do limit to 1 Gig for each field (row/col
combination) but there are techniques to manage data sets working within
these constraints.  I will let someone else who has more experience then me
working with matrices answer how is the best way to do so in a case like
you have provided.

Cheers,
Ivan

On Wed, Jan 3, 2018 at 2:22 PM, Anthony Thomas <ahthomas@eng.ucsd.edu>
wrote:

> Hi Madlib folks,
>
> I have a large tall and skinny sparse matrix which I'm trying to multiply
> by a dense vector. The matrix is 1.25e8 by 100 with approximately 1%
> nonzero values. This operations always triggers an error from Greenplum:
>
> plpy.SPIError: invalid memory alloc request size 1073741824 (context
> 'accumArrayResult') (mcxt.c:1254) (plpython.c:4957)
> CONTEXT:  Traceback (most recent call last):
>   PL/Python function "matrix_vec_mult", line 24, in <module>
>     matrix_in, in_args, vector)
>   PL/Python function "matrix_vec_mult", line 2044, in matrix_vec_mult
>   PL/Python function "matrix_vec_mult", line 2001, in
> _matrix_vec_mult_dense
> PL/Python function "matrix_vec_mult"
>
> Some Googling suggests this error is caused by a hard limit from Postgres
> which restricts the maximum size of an array to 1GB. If this is indeed the
> cause of the error I'm seeing does anyone have any suggestions about how to
> circumvent this issue? This comes up in other cases as well like
> transposing a tall and skinny matrix. MVM with smaller matrices works fine.
>
> Here is relevant version information:
>
> SELECT VERSION();
> PostgreSQL 8.3.23 (Greenplum Database 5.1.0 build dev) on
> x86_64-pc-linux-gnu, compiled by GCC gcc
>  (Ubuntu 5.4.0-6ubuntu1~16.04.5) 5.4.0 20160609 compiled on Dec 21 2017
> 09:09:46
>
> SELECT madlib.version();
> MADlib version: 1.12, git revision: unknown, cmake configuration time: Thu
> Dec 21 18:04:47 UTC 201
> 7, build type: RelWithDebInfo, build system: Linux-4.4.0-103-generic, C
> compiler: gcc 4.9.3, C++ co
> mpiler: g++ 4.9.3
>
> Madlib install-check reported one error in the "convex" module related to
> "loss too high" which seems unrelated to the issue described above. I know
> Ubuntu isn't officially supported by Greenplum so I'd like to be confident
> this issue isn't just the result of using an unsupported OS. Please let me
> know if any other information would be helpful.
>
> Thanks,
>
> Anthony
>



-- 
Ivan Novick, Product Manager Pivotal Greenplum
inovick@pivotal.io --  (Mobile) 408-230-6491
https://www.youtube.com/GreenplumDatabase

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