# Chess image, many ways to generate this image

def xadrez1(s):
    # explicit pixel scanning
    from Numeric import zeros
    a=zeros(s)
    for i in range(s[0]):
        for j in range(s[1]):
            a[i,j]=(i+j)%2
    return a

def xadrez2(s):
    #usando o meshgrid
    from ia636 import iameshgrid
    [i,j]=iameshgrid( range( s[1]), range( s[0]))
    return (i+j)%2

def xadrez3(s):
    # usando indices, particular case of meshgrid
    from Numeric import indices
    i = indices(s)
    return (i[0] + i[1]) % 2

def xadrez4(s):
    # usando o iatile
    from ia636 import iatile
    from Numeric import array
    return iatile(array([[0,1],[1,0]]),s)

def xadrez5(s):
    # usando fromfunction
    from Numeric import fromfunction
    def elementos(i,j):
        return (i+j)%2
    a = fromfunction(elementos, s)
    return a

def xadrez6(s):
    # cria duas linhas e faz o resize
    from Numeric import arange, array, resize
    r = arange(s[1]) % 2
    linha = array([r, 1 - r])
    ret = resize(linha, s)
    return ret

def xadrez7(s):
    # using slices
    from Numeric import zeros
    a = zeros(s)
    a[::2,1::2]=1
    a[1::2,::2]=1
    return a

def xadrezperf(s):
    from time import time
    funlist = (xadrez1,xadrez2,xadrez3,xadrez4,xadrez5,xadrez6,xadrez7)
    fundesc = ("pixel","grid" ,"indic","tile", "fromf","resize","slice")
    i=0
    for fun in funlist:
        t1,f,t2 = time(), fun(s), time()
        print fun, fundesc[i], t2-t1," seconds"
        i = i+1