[pypy-issue] Issue #2839: max(array) is slower than expected (pypy/pypy)

[ahorek]

New issue 2839: max(array) is slower than expected
https://bitbucket.org/pypy/pypy/issues/2839/max-array-is-slower-than-expected

ahorek:

the native implementation is slower, what is the reason?

```
import datetime
import time
import random

arr_int = [random.randint(0,10000) for _ in xrange(50000)]

def maximum_native(arr):
  return max(arr)

def maximum(arr):
  max = arr[0]
  i = 1
  length = len(arr) - 1
  while(i < length):
    i += 1
    if arr[i] > max:
      max = arr[i]
  return max

# warmup
for i in range(500):
  maximum_native(arr_int)
for i in range(500):
  maximum(arr_int)

t = time.time()
for i in range(10000):
  maximum_native(arr_int)
elapsed_time = time.time() - t
print("max native: " + str(elapsed_time) + 's')

t = time.time()
for i in range(10000):
  maximum(arr_int)
elapsed_time = time.time() - t
print("max: " + str(elapsed_time) + 's')
```

Python 2.7.13 (ab0b9caf307d, Apr 24 2018, 18:04:42)
[PyPy 6.0.0 with GCC 6.2.0 20160901] on linux2

**max native: 15.4919641018s**

**max: 0.683923959732s**