robbyt/cache.md

## cache.md

      
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              cache.md
            
          
    Intro

I wrote a program in Python called mew.
#!/usr/bin/env python

def mew(l, n, m):
    """ l = list of ints
        n = number of list members to skip
        m = multiplier 
    """
    for i in range(0, len(l), n):
        l[i] = l[i] * m
    return l

def main(args):
    d = mew(range(int(args[1])), int(args[2]), int(args[3]))
    print sum(d)
    return 0

if __name__ == "__main__":
    import sys
    main(sys.argv)
It takes a big number, the first argument, creates a list, then it multiplies (argv[3]) every n'th (argv[2]) number. Finally it sums the resulting list.
(v_csh)(master)rtmp:mew rterhaar$ time ./mew.py 134217728 16 3
10133098960257024

real 0m8.490s
user 0m6.299s
sys 0m2.189s

However if I make a couple of minor modifications and then compile that code with pypy:
#!/usr/bin/env python

def mew(l, n, m):
    """ l = list of ints
        n = number of list members to skip
        m = multiplier 
    """
    for i in range(0, len(l), n):
        l[i] = l[i] * m
    return l

def summer(l):
    """ Pypy does not support sum()
    """
    ans = 0
    for i in l:
        ans += i
    return ans

def main(args):
    d = mew(range(int(args[1])), int(args[2]), int(args[3]))
    print summer(d)
    return 0

def target(*args):
    return main, None

if __name__ == "__main__":
    import sys
    main(sys.argv)
(v_csh)(master)rtmp:mew rterhaar$ time ./mew-c 134217728 16 3
10133098960257024

real 0m0.821s
user 0m0.451s
sys 0m0.351s

it takes .8 seconds