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# The Lesson V8 Can Teach Python and Other Dynamic Languages

Being unable to completely give up math for computers, I am naturally drawn to Project Euler and as a result solved a ridiculous number of the problems posted there while learning Python. A few months ago (March 13), after reading Secrets of a Javascript Ninja, I decided to begin converting my solutions to Javascript. A month and a half later I came back to it, and then finally two months after that, I began to take it seriously.

After making this decision, I noticed the prime Sieve of Eratosthenes was mighty fast when I ran it in Chrome, maybe even faster than my beloved Python. I tabled the thought for a little, but never really forgot it. So a few weeks ago (early August 2011), I finally got a working install of node running on my machine and was able to make more of this thought. (I say finally installed because on two previous tries I gave up because of conflicts with my version of gcc, coupled with the fact that I had no good reason to use node.)

When I originally did the conversion, I had skipped problem 8, because my implementation required pulling in the problem data as text from a file. While hanging out with Boris and Eric from on the Chrome Developer Relations team, I decided to give it another go on node (xhr requests not allowed) and found it to be quite simple with readFileSync in the in the node native fs module. After witnessing this, over this weekend, I decided to harness the power of V8 — the Javascript engine that powers Chrome and node — and run all my scripts locally with node. So over a two day period, I hack-hack-hacked my way into converting the Python solutions for problems 11 through 50 (the remaining unconverted) into their Javascript equivalents, while also converting a good portion of my hefty functions module.

Once this was done, I had also found I could replace most of the nice parts about Python with my own equivalent. For example, I was able to replace functionality I needed from the Python set datatype with

function uniq(arr) {
var result = {};
for (var i = 0, val; val = arr[i]; i++) {
result[val] = true;
}
return Object.keys(result);
};


and I was able to replace the (amazingly) useful Python handling of long integers with a non-native node package called bigint that uses libgmp. Of course, for Python's secret sauce — the list comprehension — I was able to substitute enough filter, reduce, and map statements to almost make it seem like I had never left Pythonland. After doing all this, I also ended up writing my own operator.js to replace the wonderful Python native module operator, and my own timer.js to stand in for the Python native module time.

Finally, I had working code and could do a side by side comparison of V8 and the Python interpreter.

Update: I added a column for PyPy, a just in time implementation of Python.

Here is what I found (averaging the runtime over 10 separate calls to each function, the results are):

Problem Answer Python Javascript Ratio (PY/JS) PyPy
1* 233168 1804ms 1215ms 1.48 385ms
2* 4613732 247ms 102ms 2.42 85ms
3* 6857 4725ms 1508ms 3.13 582ms
4 906609 8708ms 149ms 58.44 282ms
5* 232792560 136ms 186ms 0.73 114ms
6* 25164150 10ms 4ms 2.50 6ms
7 104743 656ms 12ms 54.67 11ms
8* 40824 18045ms 5014ms 3.60 7042ms
9 31875000 610ms 3ms 203.33 8ms
10 142913828922 6628ms 167ms 39.69 116ms
11 70600674 49ms 2ms 24.50 11ms
12 76576500 5127ms 203ms 25.26 100ms
13* 5537376230 1795ms 10710ms 0.17 1423ms
14 837799 5572ms 1712ms 3.25 362ms
15* 137846528820 54ms 18ms 3.00 55ms
16* 1366 1844ms 265ms 6.96 462ms
17 21124 87ms 4ms 21.75 7ms
18* 1074 2291ms 1790ms 1.28 1090ms
19* 171 2254ms 336ms 6.71 342ms
20* 648 1061ms 9154ms 0.12 374ms
21 31626 18910ms 1038ms 18.22 728ms
22 871198282 188ms 7ms 26.86 8ms
23 4179871 83318ms 1120ms 74.39 1295ms
24* 2783915460 206ms 210ms 0.98 139ms
25 4782 5865ms 35ms 167.57 232ms
26 983 28ms 18ms 1.56 4ms
27 -59231 645738ms 22536ms 28.65 28288ms
28* 669171001 8509ms 1037ms 8.21 981ms
29 9183 184ms 96ms 1.92 20ms
30 443839 52167ms 1037ms 50.31 877ms
31 73682 9606ms 257ms 37.38 154ms
32 45228 206888ms 12096ms 17.10 4266ms
33 100 300ms 6ms 50.00 15ms
34 40730 7462ms 2447ms 3.05 247ms
35 55 8617ms 848ms 10.16 242ms
36 872187 189788ms 2183ms 86.94 3532ms
37 748317 2389022ms 71845ms 33.25 61551ms
38 932718654 506ms 10ms 50.60 12ms
39 840 178ms 6ms 29.67 12ms
40* 210 326ms 202ms 1.61 119ms
41 7652413 2627ms 133ms 19.75 65ms
42 162 65ms 7ms 9.29 8ms
43 16695334890 38ms 2ms 19.00 2ms
44 5482660 384013ms 27744ms 13.84 6621ms
45* 1533776805 17ms 4ms 4.25 8ms
46 5777 2864ms 202ms 14.18 65ms
47 134043 400967ms 12838ms 31.23 4425ms
48 9110846700 46ms 16ms 2.88 6ms
49 296962999629 115ms 8ms 14.38 13ms
50 997651 3277ms 80ms 40.96 51ms
*These were very quick to run, so the runtimes are the time taken to run 10000 times.

As you'll notice, standard Python gets its butt kicked. I was kind of saddened by this, but in the end, just giddy that our web is faster because of it (90% of my life is digital) and also that we can do scripting faster on the server side (attribute to Boris Smus) because of the node project (thanks Ryan Dahl).

Standard Python is actually slower in 46 of the 50 problems. In 28 of the 46 node is faster by a factor of 10 or greater, in 9 of those 28 by a factor of 50 or greater and in 2 of the 9 by a factor of 100 or greater! The only 4 in which Python was faster were from the n = 10000 sample. In fact, I was able to pinpoint exactly why:

• #5 - My own Javascript implementation of gcd is slower than the native (from fractions import gcd) Python library (resulting in a difference of 50 ms over 10000 iterations)
• #13 - The node package bigint is slower than the Python native long int (Javascript is slower by a factor of 6)
• #20 - The node package bigint is slower than the Python native long int (Javascript is slower by a factor of 8.5)
• #24 - Having to perform two slices is slower in Javascript than in Python and there is no good way to just remove one element (resulting in a difference of 4 ms over 10000 iterations; a little bit about that here)

So what, you ask, is that lesson I speak of? Well, Javascript didn't used to be this fast. How did it get that way? The brilliant and inspired people behind V8 rethought the Javascript compile steps and after much work, we now have code that is closer to the metal (attribute to: Eric Bidelman, i.e. closer to machine code) than we had ever had before. The use of just-in-time compilation and other incredible techniques has taken a formerly slow and clunky language (Javascript) which was used well beyond its original intended scope, and turned it into a damn fast dynamic language. Hopefully, this movement will make its way to Python and other dynamic languages and we can all have our code end up this close to the metal.

#### Update 1:

In response to the comments, I ran the same code on the same machine, but with PyPy in place of Python. This is the direction I hope standard Python goes in and commend the guys pumping out faster and faster just in time implementations over at PyPy. I went through and counted 20 node wins, 29 PyPy wins and 1 tie. (I reserve the right to update the post with more detailed metrics.) While I do commend them, the results don't really belong in this post because PyPy is still an offshoot. (However, as I understand, they both have ties to C, as PyPy uses gcc to compile to bytecode and V8 is written in C++. Feel free to supplement my knowledge in the comments.)

#### Update 2:

All benchmarking was run on my Mac Pro Desktop with a 3.2 GHz Quad-Core Intel Xeon processor and 4 cores for a total of12 GB 1066 MHz DDR3 memory. I used Python version 2.6.1, node version 0.4.9, and PyPy version 1.5 (running on top of Python 2.7.1 with GCC 4.0.1).