ENH: Allows building npy_math with static inlining

Code Overview:
    Numpy currently decouples the math function definitions in `npy_math.c.src`
    from the function declarations found in `npy_math.h`. This patch allows
    definitions to be included along with the inclusion of the `npy_math.h`
    header.

    Keeping the declarations and definitions separate is usually the right
    approach, but mathematical code like this might be better off as an
    exception to this common practice. Because the definitions are in the source
    file instead of the header, the compiler does not have any clue what lies
    underneath these math functions. This means the compiler can't make
    important optimizations like inlining and vectorization. Extensions that
    utilize these functions could greatly benefit from this, specifically
    `loops.c.src` from the umath extension.

Implementation Details:
    + Renames `npy_math.c.src` to `npy_math_internal.h.src`
    + Generates `npy_math_internal.h` from template by adding to
      `npymath_sources` list and adding `npymath` directory to include paths in
      `generate_numpyconfig_h` function of `numpy/core/setup.py`
    + Numpy's core distutils defines `#NPY_INTERNAL_BUILD` macro to make sure
      `npy_math_internal.h` is not included when other modules try to include
      public header `npy_math.h`
        - Currently do not know how to ship headers generated from template
          files
    + Adds `npy_math.c`, a file that includes the `npy_math_internal.h.src`
      file (but does not add NPY_INLINE static)
        - This is to keep the same static npy_math library as it exists now
    + Appends `numpy/npy_math.h` with `npy_math_internal.h` under condition that
      it's not being included in npy_math.c.src
        - The conditional macros mean `loops.c.src` will have definitions
          included, and the compiler will vectorize accordingly
    + Adds `NPY_INLINE` static to function declarations and definitions when
      necessary
    + Replaces `sqrtf` with `npy_sqrtf` in `numpy/core/src/umath/umath_tests.c`
      to make function portable
        - `_sqrtf` was not found on certain Windows environments compiling with
          Py2

1 files changed, 7 insertions, 2 deletions

diff --git a/numpy/core/setup.py b/numpy/core/setup.py
index 5bc2eec95..89f65f41a 100644
--- a/numpy/core/setup.py
+++ b/numpy/core/setup.py
@@ -4,6 +4,7 @@ import os
 import sys
 import pickle
 import copy
+import sysconfig
 import warnings
 from os.path import join
 from numpy.distutils import log
@@ -513,6 +514,7 @@ def configuration(parent_package='',top_path=None):
         # put private include directory in build_dir on search path
         # allows using code generation in headers headers
         config.add_include_dirs(join(build_dir, "src", "private"))
+        config.add_include_dirs(join(build_dir, "src", "npymath"))
 
         target = join(build_dir, header_dir, '_numpyconfig.h')
         d = os.path.dirname(target)
@@ -605,6 +607,7 @@ def configuration(parent_package='',top_path=None):
     config.add_include_dirs(join('src', 'umath'))
     config.add_include_dirs(join('src', 'npysort'))
 
+    config.add_define_macros([("NPY_INTERNAL_BUILD", "1")]) # this macro indicates that Numpy build is in process
     config.add_define_macros([("HAVE_NPY_CONFIG_H", "1")])
     if sys.platform[:3] == "aix":
         config.add_define_macros([("_LARGE_FILES", None)])
@@ -662,14 +665,16 @@ def configuration(parent_package='',top_path=None):
         subst_dict["posix_mathlib"] = posix_mlib
         subst_dict["msvc_mathlib"] = msvc_mlib
 
-    npymath_sources = [join('src', 'npymath', 'npy_math.c.src'),
+    npymath_sources = [join('src', 'npymath', 'npy_math_internal.h.src'),
+                       join('src', 'npymath', 'npy_math.c'),
                        join('src', 'npymath', 'ieee754.c.src'),
                        join('src', 'npymath', 'npy_math_complex.c.src'),
                        join('src', 'npymath', 'halffloat.c')
                        ]
     config.add_installed_library('npymath',
             sources=npymath_sources + [get_mathlib_info],
-            install_dir='lib')
+            install_dir='lib',
+            build_info={'include_dirs' : []})  # empty list required for creating npy_math_internal.h
     config.add_npy_pkg_config("npymath.ini.in", "lib/npy-pkg-config",
             subst_dict)
     config.add_npy_pkg_config("mlib.ini.in", "lib/npy-pkg-config",