使用MicroPython計算任意位數圓周率

計算任意精度的圓周率是個有趣的主題，得益於python的強大計算能力，咱們在MicroPython中也能夠輕鬆的計算pi的數值。

先輸入下面的代碼：

"""
文件：pi.py
說明：用MicroPython計算任意精度圓周率計算
做者：未知
版本：
時間：
修改：邵子揚
      2016.5
      v1.1
http://bbs.micro-python.com/forum.php
"""
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_us()
    t=pi(n)
    t2=time.ticks_us()
    print('elapsed: ', time.ticks_diff(t1,t2)/1000000, 's')
    return t

def pi2(n=10):
    r=6*(10**n)*1000
    p=0
    k=0
    c=r//2
    d=c//(2*k+1)
    while d>0:
        p=p+d
        k=k+1
        k2=2*k
        c=c*(k2-1)//(4*k2)
        d=c//(k2+1)
    return p//1000

def pi2_t(n=10):
    t1=time.ticks_us()
    t=pi2(n)
    t2=time.ticks_us()
    print('elapsed: ', time.ticks_diff(t1,t2)/1000000, 's')
    return t

 

咱們將它複製到STM32F7DISC中（STM32F7DISC已經下載了MicroPython固件），而後測試一下計算速度。（在其它MicroPython開發板上也能夠進行這個測試）

MicroPython v1.8 on 2016-05-15; F7DISC with STM32F746
Type "help()" for more information.
>>> import pi
>>> npi=pi.pi_t(1000)
elapsed:  0.221486 s
>>> npi=pi.pi_t(2000)
elapsed:  0.793141 s
>>> npi=pi.pi_t(5000)
elapsed:  4.981964 s
>>> npi=pi.pi_t(10000)
elapsed:  21.02012 s
>>>

從運行結果能夠看出，雖然不是很快，可是考慮到STM32的資源和性能，結果已經出乎預料了，畢竟計算函數還不到10行代碼，沒有作深度優化。最後打印出1000位的圓周率，你們能夠和標準結果比較看看。

>>> pi.pi(1000)
31415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798609437027705392171762931767523846748184676694051320005681271452635608277857713427577896091736371787214684409012249534301465495853710507922796892589235420199561121290219608640344181598136297747713099605187072113499999983729780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083814206171776691473035982534904287554687311595628638823537875937519577818577805321712268066130019278766111959092164201989
>>>