Boost.Math is a header-only library now

[rcurtin]

Reported by rcurtin on 9 Apr 42282472 10:33 UTC
As of Boost 1.37 or so (a long time ago), Boost.Math became a header-only library. Most distributions still provide a libboost-math-c99.so, but some (RHEL5 and RHEL6 base packages -- not ATrpms or other third-party repositories) do not, because it's header-only. Some investigation needs to happen here to figure out how to handle this:

1. Why do most repositories still provide a shared library for Boost.Math if it is header-only? What's in it?
2. CMake should look for the shared library; if it does not find it, it should search for the Boost.Math headers. If those aren't found, the configuration should fail; otherwise, it should be successful.

Currently, a build on RHEL5 or RHEL6 without third-party repositories fails because there is no shared library for Boost.Math.

[rcurtin]

Commented by rcurtin on 17 Oct 42605838 03:45 UTC

1. Newer versions of math_c99.so still have things in them. For example, 1.48 has

:[ ryan @ greenstreet ]: $ readelf -Ws /usr/lib/libboost_math_c99.so | grep math
   119: 0000000000010f50    28 FUNC    GLOBAL DEFAULT   12 _ZN5boost4math3tr18isfiniteIdEEbT_
   131: 0000000000010f00    68 FUNC    GLOBAL DEFAULT   12 _ZN5boost4math3tr110fpclassifyIdEEiT_
   133: 0000000000010fa0    41 FUNC    GLOBAL DEFAULT   12 _ZN5boost4math3tr18isnormalIdEEbT_
   134: 0000000000010f70    24 FUNC    GLOBAL DEFAULT   12 _ZN5boost4math3tr15isinfIdEEbT_
   135: 0000000000010f90     8 FUNC    GLOBAL DEFAULT   12 _ZN5boost4math3tr15isnanIdEEbT_
   142: 0000000000010ef0     8 FUNC    GLOBAL DEFAULT   12 _ZN5boost4math3tr17signbitIdEEbT_

and older versions have more, but it seems as though this stuff is not needed for MLPACK; that is, when I remove -lboost_math_c99, there are no problems.

1. Given that we don't need to link against it, we can just drop math_c99 from the Boost dependencies. This change was committed with r13371.