Hi Mike,
On Sun, Nov 24, 2013 at 10:46 AM, Mike Croucher
<[email protected]> wrote:
> Hi
>
> I'd like to time how long it takes sympy to evaluate 1 million digits of pi
> using ipython. I've tried in both Linux and Windows.
> Let's look at the linux one for now
>
> import sympy
> #This command takes quite a while
> pi=sympy.pi.evalf(1000000)
> #This command evaluates instantly
> pi=sympy.pi.evalf(1000000)
I don't have gmpy installed, so I tested on 100,000:
In [1]: %time s = pi.evalf(100000)
CPU times: user 0.81 s, sys: 0.00 s, total: 0.81 s
Wall time: 0.81 s
In [2]: %time s = pi.evalf(100000)
CPU times: user 0.00 s, sys: 0.00 s, total: 0.00 s
Wall time: 0.00 s
In [3]: %timeit s = pi.evalf(100000)
10000 loops, best of 3: 129 us per loop
>
> I suspected that sympy was caching the result so I did
>
> export SYMPY_USE_CACHE=no
>
> at the bash prompt before running ipython. I also tried
>
> export SYMPY_USE_CACHE="no"
>
> either way, same result.
The above caching is done in mpmath. If you apply the following patch:
diff --git a/sympy/mpmath/libmp/libelefun.py b/sympy/mpmath/libmp/libelefun.py
index 531a7d4..1da0336 100644
--- a/sympy/mpmath/libmp/libelefun.py
+++ b/sympy/mpmath/libmp/libelefun.py
@@ -93,8 +93,8 @@ def constant_memo(f):
f.memo_val = None
def g(prec, **kwargs):
memo_prec = f.memo_prec
- if prec <= memo_prec:
- return f.memo_val >> (memo_prec-prec)
+# if prec <= memo_prec:
+# return f.memo_val >> (memo_prec-prec)
newprec = int(prec*1.05+10)
f.memo_val = f(newprec, **kwargs)
f.memo_prec = newprec
Then I get:
In [1]: %time s = pi.evalf(100000)
CPU times: user 0.81 s, sys: 0.00 s, total: 0.81 s
Wall time: 0.81 s
In [2]: %time s = pi.evalf(100000)
CPU times: user 0.81 s, sys: 0.00 s, total: 0.81 s
Wall time: 0.81 s
In [3]: %timeit s = pi.evalf(100000)
1 loops, best of 3: 802 ms per loop
> Similarly if I try in windows using Windows
> environment variables and ipython via anaconda python.
>
> This is messing up %timeit
>
> What am I doing wrong please?
Nothing, you were just turning off the cache in SymPy, while
the numerical value of pi was being cached in sympy.mpmath.
Ondrej
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