[IPOL discuss] Eigen, once again...

[Nicolas Limare]

Hi,

Once again, I come back about the Eigen library. Sorry, it must look
like stubbornness...

I happen to have seen a comment in an IPOL review. I do not disclose
any detail about the IPOL article involved, so I think there is no
editorial problem with my message.

The review comment is:

> First, the Eigen library [...] does not compile with gcc 4.3.3 on
> Ubuntu 64 bits. (at least I did not succeed in compiling your 
> code with this system, the compilation stops on the files from
> Eigen). 
> No problem with gcc 4.4.1 on Ubuntu 64 bits and with gcc 4.4.3 on
> Ubuntu 32 bits. I guess that the problem is with gcc 4.3. It seems
> that this bug is not documented on the Eigen page. Now, the code of
> this library is a bit cryptic to me, so I may miss something.

The Eigen version involved is Eigen 3.0. I do not now which compiler
options were used, but I think the reviewer would have pointed them it
they were the source of the problem.

I tested with gcc v4.4.5, it works. I also tested with the Intel icc
v12.0.4 compiler, and it threw lots of warning messages on Eigen, but
could compile. I tested with Sun suncc v12.2 compiler and it aborted
on Eigen because of too many error messages. I tested with the LLVM
clang v1.1 compiler and it died on Eigen.

The Eigen web site says "Eigen has good compiler support as we run our
test suite against many compilers to guarantee reliability and work
around any compiler bugs. Eigen also is standard C++98 and maintains
very reasonable compilation times."

From these quick tests, I doubt the validity of this assertion, at
least for the 3.0 version. It reinforces my feeling that Eigen is not
suitable for IPOL.

-- 
Nicolas LIMARE - CMLA - ENS Cachan    http://www.cmla.ens-cachan.fr/~limare/
IPOL - image processing on line                          http://www.ipol.im/
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