Styjun

I have the following code in python to calculate the Mandelbrot set. It works fine, but when I try to compile it with JIT by adding @jit decorator before the function def, it doesn't work any more. Can anybody tell me why? I would appreciate if you don't criticize my Mandelbrot calculation (I am guessing it could be optimized) and just let me know why JIT doesn't work with this function. By the way, the code is indented after the def. It just didn't appear that way when I inserted it here.

def mandelbrot(xmin,xmax,ymin,ymax,width,height,maxiter):
points=[]
x=np.linspace(xmin,xmax,width)
y=np.linspace(ymin,ymax,height)
for ix,re in enumerate(x):
 points.append([])
 for iy,im in enumerate(y):
 cx=re
 cy=im
 zx=0
 zy=0
 for n in range(maxiter):
 if zx*zx+zy*zy>4.0:
 iters=n
 break
 else:
 oldzx=zx
 oldzy=zy
 zy = 2*oldzx*oldzy+cy
 zx = oldzx*oldzx-oldzy*oldzy+cx 
 iters=n
 points[ix].append(int(iters))
return points

I get the following error report with the final line being LoweringError

runfile('D:/python programs/mandelbrot/mandelbrot.py', wdir='D:/python
programs/mandelbrot') Traceback (most recent call last):

File "", line 1, in
runfile('D:/python programs/mandelbrot/mandelbrot.py', wdir='D:/python programs/mandelbrot')

File
"C:UsersMatthewAnaconda3libsite-packagesspyder_kernelscustomizespydercustomize.py",
line 786, in runfile
execfile(filename, namespace)

File
"C:UsersMatthewAnaconda3libsite-packagesspyder_kernelscustomizespydercustomize.py",
line 110, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)

File "D:/python programs/mandelbrot/mandelbrot.py", line 41, in

mandelbrot_set=mandelbrot(-2.0,1.0,-1.5,1.5,500,500,50)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbadispatcher.py",
line 368, in _compile_for_args
raise e

File
"C:UsersMatthewAnaconda3libsite-packagesnumbadispatcher.py",
line 325, in _compile_for_args
return self.compile(tuple(argtypes))

File
"C:UsersMatthewAnaconda3libsite-packagesnumbadispatcher.py",
line 653, in compile
cres = self._compiler.compile(args, return_type)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbadispatcher.py",
line 83, in compile
pipeline_class=self.pipeline_class)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
873, in compile_extra
return pipeline.compile_extra(func)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
367, in compile_extra
return self._compile_bytecode()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
804, in _compile_bytecode
return self._compile_core()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
791, in _compile_core
res = pm.run(self.status)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
253, in run
raise patched_exception

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
245, in run
stage()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
438, in stage_objectmode_frontend
cres = self.frontend_looplift()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
428, in frontend_looplift
lifted=tuple(loops), lifted_from=None)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
887, in compile_ir
lifted_from=lifted_from)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
375, in compile_ir
return self._compile_ir()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
811, in _compile_ir
return self._compile_core()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
791, in _compile_core
res = pm.run(self.status)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
253, in run
raise patched_exception

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
245, in run
stage()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
652, in stage_objectmode_backend
self._backend(lowerfn, objectmode=True)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
628, in _backend
lowered = lowerfn()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
601, in backend_object_mode
self.flags)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbacompiler.py", line
1018, in py_lowering_stage
lower.lower()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbalowering.py", line
173, in lower
self.lower_normal_function(self.fndesc)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbalowering.py", line
214, in lower_normal_function
entry_block_tail = self.lower_function_body()

File
"C:UsersMatthewAnaconda3libsite-packagesnumbalowering.py", line
239, in lower_function_body
self.lower_block(block)

File
"C:UsersMatthewAnaconda3libsite-packagesnumbalowering.py", line
254, in lower_block
self.lower_inst(inst)

File "C:UsersMatthewAnaconda3libcontextlib.py", line 130, in
exit
self.gen.throw(type, value, traceback)

File "C:UsersMatthewAnaconda3libsite-packagesnumbaerrors.py",
line 585, in new_error_context
six.reraise(type(newerr), newerr, tb)

File "C:UsersMatthewAnaconda3libsite-packagesnumbasix.py",
line 659, in reraise
raise value

LoweringError: iters

File "mandelbrot.py", line 17: def
mandelbrot(xmin,xmax,ymin,ymax,width,height,maxiter):

for ix,re in enumerate(x):
points.append([])
^

I solved the problem. It seems I need to initialize the variable 'iters' to 0 at the start of the loop. So this works when I put @jit before it. Anybody know why?

def mandelbrot(xmin,xmax,ymin,ymax,width,height,maxiter):
points=[]
x=np.linspace(xmin,xmax,width)
y=np.linspace(ymin,ymax,height)
for ix,re in enumerate(x):
 points.append([])
 for iy,im in enumerate(y):
 iters=0
 cx=re
 cy=im
 zx=0
 zy=0
 for n in range(maxiter):
 if zx*zx+zy*zy>4.0:
 iters=n
 break
 else:
 oldzx=zx
 oldzy=zy
 zy = 2*oldzx*oldzy+cy
 zx = oldzx*oldzx-oldzy*oldzy+cx 
 iters=n
 points[ix].append(iters)
return points