# Problem with OpenMP in Ruby extension

**URL:** <https://www.ruby-forum.com/t/problem-with-openmp-in-ruby-extension/116270>\
**Category:** Ruby\
**Created:** [October 3, 2007, 11:54pm UTC](https://www.ruby-forum.com/t/problem-with-openmp-in-ruby-extension/116270 "2007-10-03T23:54:06Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Rudi\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aca169/32.png) [@Rudi\_C](https://www.ruby-forum.com/u/Rudi_C)\
**Post date:** [October 3, 2007, 11:54pm UTC](https://www.ruby-forum.com/t/problem-with-openmp-in-ruby-extension/116270/1 "2007-10-03T23:54:06Z")

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Hi everybody,

I am the main developer of CompLearn, an open-source machine learning  
library  
for scientific researchers. I have written a Ruby binding for CompLearn  
called complearn-ruby. It has worked fine in the past. But it has a  
problem  
ever since I converted the base library (libcomplearn) to use OpenMP for  
multicore processor support. If I just try to use the simplest approach  
that  
has worked in the past in my extconf.rb, I get the following problem  
when I  
try to require the C-extension Ruby binding complearn4r.so and use the  
multicore part of the system:

ruby: symbol lookup error: /usr/lib/libcomplearn.so.1: undefined symbol:  
GOMP\_pa  
rallel\_start

To try to fix this error,

I adjusted the extconf.rb to include this line:

have\_library(‘gomp’, ‘main’)

And rebuilding works but running a simple test program (just trying to  
require  
complearn) fails in a different way than before:

/home/cilibrar/rlc/projects/complearn/complearn-ruby/ext/complearn/complearn4r.s  
o: libgomp.so.1: shared object cannot be dlopen()ed -  
/home/cilibrar/rlc/project  
s/complearn/complearn-ruby/ext/complearn/complearn4r.so (LoadError)  
from  
/home/cilibrar/rlc/projects/complearn/complearn-ruby/lib/complearn.  
rb:2  
from tests/t2.rb:1:in `require’  
from tests/t2.rb:1

I don’t know what else to try and wonder if anybody else can offer a  
clue?

I have tried for a long time experimenting with CFLAGS, CPPFLAGS,  
LDFLAGS,  
and -fopenmp among other settings but I still cannot seem to figure out  
a solution. I have put the source code for this problem up at

[http://cilibrar.com/~cilibrar/projsup/rubbug/libcomplearn-1.0.4.tar.gz](http://cilibrar.com/~cilibrar/projsup/rubbug/libcomplearn-1.0.4.tar.gz)  
and  
[http://cilibrar.com/~cilibrar/projsup/rubbug/libcomplearn-ruby-1.0.4.tar.gz](http://cilibrar.com/~cilibrar/projsup/rubbug/libcomplearn-ruby-1.0.4.tar.gz)

I would appreciate greatly any help anybody can offer in this problem.  
Thank  
you for your attention,

Rudi

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<div class="post-metadata">

**Author:** ![Rudi\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aca169/32.png) [@Rudi\_C](https://www.ruby-forum.com/u/Rudi_C)\
**Post date:** [October 4, 2007, 6:49am UTC](https://www.ruby-forum.com/t/problem-with-openmp-in-ruby-extension/116270/2 "2007-10-04T06:49:07Z")

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On Oct 3, 2007, at 3:53 PM, Rudi C. wrote:

> I adjusted the extconf.rb to include this line:
> 
> have\_library(‘gomp’, ‘main’)
> 
> And rebuilding works but running a simple test program (just trying  
> to require  
> complearn) fails in a different way than before:

this sounds like it gets the link right (LD\_LIBRARY\_PATH) but fails  
at runtime. try setting LD\_RUN\_PATH to the location of the gomp lib  
_before_ compiling

for example

export LD\_RUN\_PATH=/full/path/to/directory/with/gomp/lib  
ruby extconf.rb && make && sudo make install

just a hunch…

cheers.

ps. long time time no hear!

a @ [http://drawohara.com/](http://drawohara.com/)

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<div class="post-metadata">

**Author:** ![Rudi\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aca169/32.png) [@Rudi\_C](https://www.ruby-forum.com/u/Rudi_C)\
**Post date:** [October 4, 2007, 1:22pm UTC](https://www.ruby-forum.com/t/problem-with-openmp-in-ruby-extension/116270/3 "2007-10-04T13:22:29Z")

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Hi Ara,

Good to hear from you and I am glad to hear you are still thinking about  
dynamic  
linking issues. Unfortunately I tried your suggestion and so far I  
cannot detect any measurable difference in behavior. Same error  
messages in both cases, with and without the #have\_library(gomp…)  
line.

Yes, it has taken years but I have rewritten complearn to use gobject  
and OpenMP and I must say the results are exciting. Recently,  
somebody sent in a patch to improve the complearn tree search from  
O(n^5) to O(n^3) and this really made my week last week, speeding up  
tree search by thousands of times. I am very excited to start  
applying the new technology but this whole ruby extension thing openmp  
problem has rained on my parade! nice to hear from you again, -r.

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<div class="post-metadata">

**Author:** ![Rudi\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aca169/32.png) [@Rudi\_C](https://www.ruby-forum.com/u/Rudi_C)\
**Post date:** [October 6, 2007, 5:34pm UTC](https://www.ruby-forum.com/t/problem-with-openmp-in-ruby-extension/116270/4 "2007-10-06T17:34:35Z")

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On Oct 4, 5:22 am, “Rudi C.” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> somebody sent in a patch to improve the complearn tree search from  
> O(n^5) to O(n^3) and this really made my week last week, speeding up  
> tree search by thousands of times. I am very excited to start  
> applying the new technology but this whole ruby extension thing openmp  
> problem has rained on my parade! nice to hear from you again, -r.

try setting LD\_LIBRARY\_PATH to the location of libgimp (directory  
containing lib) and see if that helps

for example

export LD\_LIBRARY\_PATH=/usr/local/lib/  
ruby a.rb

and see if you still get the error. if dlopen fails then there is  
some other issue. make sure the lib is actually there - if it this  
works then massaging LD\_RUN\_PATH _should_ work.

regards.

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<div class="post-metadata">

**Author:** ![Rudi\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aca169/32.png) [@Rudi\_C](https://www.ruby-forum.com/u/Rudi_C)\
**Post date:** [October 6, 2007, 9:09pm UTC](https://www.ruby-forum.com/t/problem-with-openmp-in-ruby-extension/116270/5 "2007-10-06T21:09:27Z")

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Hmm, I tried the LD\_LIBRARY\_PATH thing and still no luck. But, gga gave  
the  
suggestion that perhaps it is a bad idea (or even now crashing) for the  
other  
reason that Ruby has its own threads that are probably grossly  
incompatible  
with OpenMP threading. So, I instead rewrote the entire Ruby binding  
and also  
made a new standalone application called uncd: the Universal NCD  
connectort.  
It uses stdin and stdout with a handmade protocol to communicate with  
a server process to allow easy language binding in Ruby and Erlang and  
eventually Perl, Java, Python etc. Here is the source code if you are  
interested I think it is a major improvement over the old code and  
will be doing this for future bindings too I think:

[http://hg.cilibrar.com/complearn-uncd/](http://hg.cilibrar.com/complearn-uncd/)

I learned this approach from Erlang books. I think I like the idea of  
coarse-grained libraries providing functionality via separate  
process-space as we move into ubiquitous multicore land.

Thanks for taking the time to try some answers I always have more to  
learn about the LD\_\* variables and dynamic linking.

best regards,

-r.