From c74c3e0ba75ea10f93d8d40e4c796d1c442c070b Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Mon, 18 Oct 2021 12:12:08 +0200
Subject: interp: add 2D Lagrangian interpolation in C

---
 interp.py | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

(limited to 'interp.py')

diff --git a/interp.py b/interp.py
index f0f5693..9e4049e 100644
--- a/interp.py
+++ b/interp.py
@@ -1,3 +1,5 @@
+import ctypes
+
 import numpy as np
 
 def interp1d(src_start, src_step, src_val, dst_coords, stencil):
@@ -50,3 +52,65 @@ def interp2d(src_start, src_step, src_val, dst_coords, stencil):
         ret += fact[0][i] * val
 
     return ret
+
+_doubleptr = ctypes.POINTER(ctypes.c_double)
+
+class Interp2D_C:
+    _lib    = None
+    _interp_func = None
+
+    _src_start_c  = None
+    _src_step_c   = None
+    _src_val_c    = None
+    _src_stride_c = None
+    _src_len_c    = None
+
+    _x     = None
+    _y     = None
+    _ret   = None
+    _x_c   = None
+    _y_c   = None
+    _ret_c = None
+
+    def __init__(self, src_start, src_step, src_val, stencil):
+        self._lib = ctypes.CDLL('lib_interp_c.so')
+
+
+        func = getattr(self._lib, 'interp2d_%d' % stencil)
+        func.argtypes = [_doubleptr, _doubleptr, _doubleptr,
+            ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int),
+            ctypes.c_int, _doubleptr, _doubleptr, _doubleptr]
+
+        self._interp_func = func
+
+        self._src_start_c  = (ctypes.c_double * 2)(src_start[0], src_start[1])
+        self._src_step_c   = (ctypes.c_double * 2)(src_step[0],  src_step[1])
+        self._src_val_c    = ctypes.cast(np.ctypeslib.as_ctypes(src_val), _doubleptr)
+        self._src_stride_c = (ctypes.c_int * 2)(src_val.strides[0] // 8, src_val.strides[1] // 8)
+        self._src_len_c    = (ctypes.c_int * 2)(src_val.shape[0], src_val.shape[1])
+
+        self._setup_arrays((1,))
+
+    def _setup_arrays(self, shape):
+        self._x   = np.empty(shape)
+        self._y   = np.empty(shape)
+        self._ret = np.empty(shape)
+
+        self._x_c   = ctypes.cast(np.ctypeslib.as_ctypes(self._x),   _doubleptr)
+        self._y_c   = ctypes.cast(np.ctypeslib.as_ctypes(self._y),   _doubleptr)
+        self._ret_c = ctypes.cast(np.ctypeslib.as_ctypes(self._ret), _doubleptr)
+
+    def interp(self, x, y):
+        if x.shape != self._x.shape:
+            self._setup_arrays(x.shape)
+
+        np.copyto(self._x,   x)
+        np.copyto(self._y,   y)
+        self._interp_func(self._src_start_c, self._src_step_c, self._src_val_c,
+                          self._src_stride_c, self._src_len_c,
+                          self._x.shape[0],
+                          self._x_c, self._y_c, self._ret_c)
+        return self._ret.copy()
+
+    def __call__(self, x, y):
+        return self.interp(x, y)
-- 
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