How to making a Julia set from Python to pycuda

Question

I've making a set of Julia using Pycuda in Python. However, an error appears. I don't know the reason for the error.

Here's the code:

import ctypes
import numpy as np
import cv2
import pycuda.driver as cuda
import pycuda.autoinit
import numpy
from pycuda.compiler import SourceModule

bmp = np.zeros((1000,1000), dtype=np.float32)
ptr = bmp.ctypes.data_as(ctypes.c_void_p)
bmp = bmp.astype(numpy.float32)
a_gpu = cuda.mem_alloc(bmp.nbytes)
cuda.memcpy_htod(a_gpu, bmp)

mod = SourceModule(""" 
    struct cuComplex {
        float r; float i;
        __device__ cuComplex(float a, float b) : r(a),i(b) {}
        __device__ float magnitude2(void) { return r * r + i * i; }
        __device__ cuComplex operator* (const cuComplex& a){
            return cuComplex(r * a.r - i * a.i, i * a.r + r * a.i);}
        __device__ cuComplex operator+ (const cuComplex& a){
            return cuComplex(r + a.r, i + a.i);}
    };    
    __device__ int julia(int x, int y){
        const float scale = 1.5;
        float jx = scale * (float)(1000/2-x)/(1000/2);
        float jy = scale * (float)(1000/2-y)/(1000/2);
        
        cuComplex c(-0.8,0.156);
        cuComplex a(jx,jy);
        
        for (int i = 0;i<200;i++){
            a = a * a + c;
            if(a.magnitude2()>1000)
                return 0;
        }
        return 1;
    }
    __global__ void juliaSet(float *ptr)
    {
        int x = blockIdx.x;
        int y = blockIdx.y;
        int offset = x + y * gridDim.x;
        
        int juliaValue = julia(x,y);
        ptr[offset*4+0]=255*juliaValue;
        ptr[offset*4+1]=0;
        ptr[offset*4+2]=0;
        ptr[offset*4+3]=255;
    }
    """)
func = mod.get_function("juliaSet")
bmp_kernel = numpy.empty_like(bmp)
func(a_gpu,block=(1000,1000,1))
cuda.memcpy_dtoh(bmp_kernel, a_gpu)
cv2.imshow('bmp', bmp)
cv2.waitKey()

error is:

Traceback (most recent call last):
File "C:\Users\hyeri\PycharmProjects\pythonProject\JuliaSet.py", line 55, in <module>
  func(a_gpu,block=(1000,1000,1))
File "C:\Users\hyeri\AppData\Local\conda\conda\envs\pycuda\lib\site-packages\pycuda\driver.py", line 480, in function_call
  func._set_block_shape(*block)
pycuda._driver.LogicError: cuFuncSetBlockShape failed: invalid argument