【RTT-MPY】不太成功的圆周率测试

发布于 2018-07-26 21:01:49 浏览：2169 订阅该版

[tocm]

这一篇本来前几天就预备写，但是因为加班耽误了。以前用python计算圆周率，用来测试CPU的性能，于是想在SWM320上也测试一下，看看性能在什么水平。圆周率的计算方法如下：

```import time

def pi(places=10):
  # 3 + 3*(1/24) + 3*(1/24)*(9/80) + 3*(1/24)*(9/80)*(25/168)
  # The numerators 1, 9, 25, ... are given by (2x + 1) ^ 2
  # The denominators 24, 80, 168 are given by (16x^2 -24x + 8)
  extra = 8
  one = 10 ** (places+extra)
  t, c, n, na, d, da = 3*one, 3*one, 1, 0, 0, 24

while t > 1: 
    n, na, d, da = n+na, na+8, d+da, da+32
    t = t * n // d
    c += t
  return c // (10 ** extra)

def pi_t(n=10):
    t1=time.ticks_ms()
    t=pi(n)
    t2=time.ticks_ms()
    print('elapsed: ', time.ticks_diff(t2,t1)/1000, 's')
    return t```

将代码用ctrl-E粘贴到micropython中，就可以进行计算了。但是系统gc机制影响了计算，使得计算时间不准确，就无法进行比较了。

```>>> a=pi_t(10)
elapsed: _space_0.02_space_s
>>> a=pi_t(20)
GC: total: 7936, used: 1840, free: 6096
No. of 1-blocks: 29, 2-blocks: 5, max blk sz: 37, max free sz: 203
elapsed: _space_0.05_space_s
>>> a=pi_t(100)
GC: total: 7936, used: 1952, free: 5984
No. of 1-blocks: 24, 2-blocks: 5, max blk sz: 37, max free sz: 158
GC: total: 7936, used: 2064, free: 5872
No. of 1-blocks: 25, 2-blocks: 5, max blk sz: 37, max free sz: 158
GC: total: 7936, used: 2016, free: 5920
No. of 1-blocks: 25, 2-blocks: 8, max blk sz: 37, max free sz: 158
GC: total: 7936, used: 1984, free: 5952
No. of 1-blocks: 25, 2-blocks: 7, max blk sz: 37, max free sz: 158
GC: total: 7936, used: 1984, free: 5952
No. of 1-blocks: 25, 2-blocks: 7, max blk sz: 37, max free sz: 158
GC: total: 7936, used: 1920, free: 6016
No. of 1-blocks: 25, 2-blocks: 5, max blk sz: 37, max free sz: 158
elapsed: _space_0.24_space_s```

希望尽早出一个改进的版本。