fix bugs, add fractal_ctypes.py

Author: mattip

create_fractal.py

@@ -1,17 +1,10 @@
-#And for desert:
-import sys
-print(sys.executable)
-from timeit import default_timer as timer
-import cffi
-from PIL import Image
-
-ffi = cffi.FFI()
+from __future__ import print_function, division
 
 class Img(object):
     def __init__(self, width, height):
         self.width = width
         self.height = height
-        self.data = ffi.new('uint8_t[%d]' % (width*height,))
+        self.data = bytearray(width*height)
 
 def create_fractal(image, iters, func, oneval):
     ''' Call a function for each pixel in the image, where
@@ -45,15 +38,20 @@ def mandel(x, y, max_iters, value):
     value[0] = max_iters
     return max_iters
 
-# Pure python
-width = 1500
-height = 1000
-image = Img(width, height)
-s = timer()
-oneval = ffi.new('uint8_t[1]')
-create_fractal(image, 20, mandel, oneval)
-e = timer()
-pure_pypy = e - s
-print('pure pypy required {:.2f} millisecs'.format(pure_pypy))
-im = Image.fromarray(image.data.reshape(height, width))
-im.save('pypyy.png')
+if __name__ == '__main__':
+    from timeit import default_timer as timer
+    from PIL import Image
+    # Pure python
+    width = 1500
+    height = 1000
+    image = Img(width, height)
+    s = timer()
+    oneval = bytearray(1)
+    create_fractal(image, 20, mandel, oneval)
+    e = timer()
+    elapsed = e - s
+    import platform
+    imp = platform.python_implementation().lower()
+    print('pure {} required {:.2f} millisecs'.format(imp, 1000*elapsed))
+    im = Image.frombuffer("L", (width, height), image.data, "raw", "L", 0, 1)
+    im.save('{}.png'.format(imp))

fractal_ctypes.py

@@ -0,0 +1,74 @@
+from __future__ import print_function, division
+import subprocess
+import os
+
+width = 1500
+height = 1000
+#ctypes
+# First all the declarations. Each function and struct must be redefined ...
+import ctypes
+
+class CtypesImg(ctypes.Structure):
+    _fields_ = [('width', ctypes.c_int),
+                ('height', ctypes.c_int),
+                ('data', ctypes.POINTER(ctypes.c_uint8)), # HUH?
+               ]
+    array_cache = {}
+    def __init__(self, width, height):
+        self.width = width
+        self.height = height
+        # Create a class type to hold the data.
+        # Since this creates a type, cache it for reuse rather
+        # than create a new one each time
+        if width*height not in self.array_cache:
+            self.array_cache[width*height] = ctypes.c_uint8 * (width * height)
+        # Note this keeps the img.data alive in the interpreter
+        self.data = self.array_cache[width*height]() # !!!!!!
+
+    def asmemoryview(self):
+        # There must be a better way, but this code will not
+        # be timed, so explicit trumps implicit
+        ret = self.array_cache[width*height]()
+        for i in range(width*height):
+            ret[i] = self.data[i]
+        return ret
+
+ctypesimg = CtypesImg(width, height)
+
+    
+# Load the DLL
+cdll = ctypes.cdll.LoadLibrary('./libcreate_fractal.so')
+
+#Fish the function pointers from the DLL and define the interfaces
+create_fractal_ctypes = cdll.create_fractal
+create_fractal_ctypes.argtypes = [CtypesImg, ctypes.c_int]
+
+mandel_ctypes = cdll.mandel
+mandel_ctypes.argtypes = [ctypes.c_float, ctypes.c_float, ctypes.c_int, 
+                          ctypes.POINTER(ctypes.c_uint8)]
+
+
+if __name__ == "__main__":
+    from timeit import default_timer as timer
+    from PIL import Image
+    from create_fractal import create_fractal
+    s = timer()
+    create_fractal_ctypes(ctypesimg, 20)
+    e = timer()
+    ctypes_onecall = e - s
+    print('ctypes calling create_fractal required {:.2f} millisecs'.format(1000*ctypes_onecall))
+    data = ctypesimg.asmemoryview()
+    print(max(data))
+    im = Image.frombuffer("L", (width, height), data, 'raw', 'L', 0, 1)
+    im.save('ctypes_fractal.png')
+
+    value = (ctypes.c_uint8*1)()
+    s = timer()
+    create_fractal(ctypesimg, 20, mandel_ctypes, value)
+    e = timer()
+    ctypes_createfractal = e - s
+    data = ctypesimg.asmemoryview()
+    print(max(data))
+    print('ctypes calling mandel required {:.2f} millisecs'.format(1000*ctypes_createfractal))
+    im = Image.frombuffer("L", (width, height), data, 'raw', 'L', 0, 1)
+    im.save('ctypes_mandel.png')