Add <cmath> header to fix ambiguity for abs

[sloede]

While trying to build OpenFHE using BinaryBuilder.jl, I received some method ambiguity errors for the use of abs on macOS, on both aarch64 (log) and x86_64 (log):

In file included from /workspace/srcdir/openfhe-development/src/core/lib/utils/utilities.cpp:36:
/workspace/srcdir/openfhe-development/src/core/include/utils/utilities.h:118:12: error: call to 'abs' is ambiguous
    return std::abs(d) > static_cast<double>(Max64BitValue());
           ^~~~~~~~
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/stdlib.h:129:6: note: candidate function
int      abs(int) __pure2;
         ^
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/c++/v1/stdlib.h:111:44: note: candidate function
inline _LIBCPP_INLINE_VISIBILITY long      abs(     long __x) _NOEXCEPT {return  labs(__x);}
                                           ^
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/c++/v1/stdlib.h:113:44: note: candidate function
inline _LIBCPP_INLINE_VISIBILITY long long abs(long long __x) _NOEXCEPT {return llabs(__x);}
                                           ^
In file included from /workspace/srcdir/openfhe-development/src/core/lib/utils/utilities.cpp:36:
/workspace/srcdir/openfhe-development/src/core/include/utils/utilities.h:135:16: error: call to 'abs' is ambiguous
        return std::abs(d) <= static_cast<double>(std::numeric_limits<int32_t>::max());
               ^~~~~~~~
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/stdlib.h:129:6: note: candidate function
int      abs(int) __pure2;
         ^
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/c++/v1/stdlib.h:111:44: note: candidate function
inline _LIBCPP_INLINE_VISIBILITY long      abs(     long __x) _NOEXCEPT {return  labs(__x);}
                                           ^
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/c++/v1/stdlib.h:113:44: note: candidate function
inline _LIBCPP_INLINE_VISIBILITY long long abs(long long __x) _NOEXCEPT {return llabs(__x);}
                                           ^
In file included from /workspace/srcdir/openfhe-development/src/core/lib/utils/utilities.cpp:36:
/workspace/srcdir/openfhe-development/src/core/include/utils/utilities.h:137:16: error: call to 'abs' is ambiguous
        return std::abs(d) <= static_cast<double>(Max64BitValue());
               ^~~~~~~~
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/stdlib.h:129:6: note: candidate function
int      abs(int) __pure2;
         ^
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/c++/v1/stdlib.h:111:44: note: candidate function
inline _LIBCPP_INLINE_VISIBILITY long      abs(     long __x) _NOEXCEPT {return  labs(__x);}
                                           ^
/opt/x86_64-apple-darwin14/x86_64-apple-darwin14/sys-root/usr/include/c++/v1/stdlib.h:113:44: note: candidate function
inline _LIBCPP_INLINE_VISIBILITY long long abs(long long __x) _NOEXCEPT {return llabs(__x);}
                                           ^
3 errors generated.

By including <cmath> in src/core/include/utils/utilities.h, this error seems to be fixed.

[dsuponitskiy]

We encourage all OpenFHE users to post their questions and suggestions to this forum.
For this particular case, I have opened a new issue and mentioned this PR in its description.

[sloede]

Thanks! My personal experience is that a PR with a concrete change set is often more descriptive than a prose description in a forum, but I'll try to follow the proper procedure next time.

What about the already existing PR #634? Any chance you could have a look at this as well? Please let me know if I should do anything to it to make it easier for the maintainers (e.g., change the target to dev etc.)

[dsuponitskiy]

This issue (to include ) was more urgent (like a bug) as it prevented you from building the libraries, so I tried to fix it asap. At the moment I am not sure how we are going to proceed with PR #634. I would need to discuss this with my colleague(s) first.