Rdio Software Engineer Alex Gaynor (@alex_gaynor) took to the #Waza 2013 stage (Heroku's Developer Conference) to talk about "Why Python, Ruby and Javascript are Slow". Gaynor argues that developers should aim to make performance beautiful. For more from Gaynor or to contact him, ping him at @Alex_Gaynor. For more on Waza visit http://waza.heroku.com/2013. For Waza videos stay tuned at http://blog.heroku.com or visit http://vimeo.com/herokuwaza

1. Why Python, Ruby, and
Javascript are slow
Alex Gaynor
Waza 2013

2. You may know me
from...

3. rdio.com

4. • CPython
• Django
• PyPy

5. Twitter rants about
how computers are bad

6. Topaz
topazruby.com

7. There is no benchmark
but your benchmark

8. Lame Excuses about
why they’re Slow

9. Dynamic Typing

10. “You can monkey patch
anything”

11. Harder to Optimize
vs.
Slow

12. The Truth

13. Let’s talk about C

14. struct Point {
double x;
double y;
double z;
};

15. class Point(object):
def __init__(self, x, y, z):
self.x = x
self.y = y
self.z = z

16. data = {
"x" x,
"y": y,
"z": z,
}

17. Dictionary
vs.
Object

18. std::hash_set<std::string, double> point;
point["x"] = x;
point["y"] = y;
point["z"] = z;

19. And it would be slow

20. Why don’t people care?

21. Let’s talk about strings

22. Given a string
matching: “w+-d+”
return the integral part
of the value

23. int(s.split("-", 1)[1])

24. atoi(strchr(s, '-') + 1)

25. Things that take time
• Hash table lookups
• Allocations
• Copying

26. The C way:
BYOB

27. char *data = malloc(1024);
while (true) {
read(fd, data, 1024);
char *start = data;
while (start < data + 1024) {
if (isspace(*start)) {
break;
}
start++;
}
printf("%sn", start);
}

28. while True:
data = os.read(fd, 1024)
print data.lstrip()

29. long *squares(long n) {
long *sq = malloc(sizeof(long) * n);
for (long i = 0; i < n; i++) {
sq[i] = i * i;
}
return sq;
}

30. def squares(n):
sq = []
for i in xrange(n):
sq.append(i * i)
return sq

31. Missing APIs

32. from __pypy__ import newlist_hint
def squares(n):
sq = newlist_hint(n)
for i in xrange(n):
sq.append(i * i)
return sq

33. Don’t make us add
heuristics

34. Heuristics = WAG

35. Growing divide
between optimizing and
not

36. Recap
• Line for line these languages are fast!
• Take care in data structures (data structure
heuristics are the WORST)
• We need better no-copy/preallocate APIs

37. Don’t abandon beauty,
simplicity, our values for
performance
Make performance
beautiful.

38. Thank you!
https://speakerdeck.com/alex
@alex_gaynor

39. If there’s time
• Java collections vs. Array and Hash. Need
more choices.
• Stop writing C extensions, use something
like cffi
• Teach good benchmarking practices