numpy: enable openblas (#3305)

* numpy: enable openblas

* libopenblas: disable dynamic arch

* Add doc for numpy

---------

Co-authored-by: Mathias Lindström <8863149+kuzeyron@users.noreply.github.com>

Author: T-Dynamos

doc/source/apis.rst

@@ -80,6 +80,17 @@ https://developer.android.com/reference/android/Manifest.permission
 Other common tasks
 ------------------
 
+Using NumPY
+~~~~~~~~~~~
+
+It should work out of the box; just ensure `numpy` is included in your requirements.
+If you want better performance, you can also add `libopenblas` to the requirements.
+This allows NumPy to use BLAS/LAPACK acceleration, which can significantly improve linear algebra operations.
+
+Keep in mind that `libopenblas` is a fairly large library (~12 MB per architecture),
+so it will increase your app size. For example, if you build for 4 architectures,
+the APK size may increase by roughly `12 × 4 = 48 MB` (before compression).
+
 Running executables
 ~~~~~~~~~~~~~~~~~~~
 

pythonforandroid/recipes/libopenblas/__init__.py

@@ -33,6 +33,7 @@ def build_arch(self, arch):
                 "-DCMAKE_BUILD_TYPE=Release",
                 "-DBUILD_SHARED_LIBS=ON",
                 "-DC_LAPACK=ON",
+                "-DDYNAMIC_ARCH=0",
                 "-DTARGET={target}".format(
                     target={
                         "arm64-v8a": "ARMV8",

pythonforandroid/recipes/numpy/__init__.py

@@ -11,6 +11,7 @@ class NumpyRecipe(MesonRecipe):
     version = "v2.3.0"
     url = "git+https://github.com/numpy/numpy"
     extra_build_args = ["-Csetup-args=-Dblas=none", "-Csetup-args=-Dlapack=none"]
+    opt_depends = ["libopenblas"]
     need_stl_shared = True
     min_ndk_api_support = 24
 
@@ -41,6 +42,19 @@ def get_recipe_env(self, arch, **kwargs):
             "android-build",
             "python",
         )
+        blas_dir = join(Recipe.get_recipe("libopenblas", self.ctx
+        ).get_build_dir(arch.arch), "build")
+        blas_incdir = blas_dir
+        blas_libdir = join(blas_dir, "lib")
+        env["CXXFLAGS"] += f" -I{blas_incdir} -L{blas_libdir}"
+
+        if 'libopenblas' in self.ctx.recipe_build_order:
+            self.extra_build_args = [
+                "-Csetup-args=-Dblas=auto",
+                "-Csetup-args=-Dlapack=auto",
+                "-Csetup-args=-Dallow-noblas=False",
+            ]
+
         return env
 
     def get_hostrecipe_env(self, arch=None):