Comment by bsdetector | Hacker News Reader

Comment by bsdetector | Hacker News Reader

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  "...my personal point of view, which now happens
  to include a lot more information from inside this
  company that I work for. ... "

More like you are sharing your personal view, having drunk the Kool-Aid.

You said Dart VM is free and can be added to any browser -- except it has deep roots into the Chrome code so this is a ton of work to do (global garbage collector between Dart, JS, DOM for instance).

You said you "ensure that programs behave the same in dart2js and the VM, and that the JS output is very fast" when dart2js doesn't support big integers or operator overloading on any numbers, among other differences, and it's ~30% slower than normal JavaScript (is much slower than TypeScript code for instance).

Dart designers have for a year now knowingly lied about dart2js DeltaBlue benchmark performance (they optimized DeltaBlue when porting it to Dart, then compared the optimized version back to the original JS). For me, I would never use a product who's designers lie to me about it.

  can you imagine what it's like to have the company you work for called "evil"...

I really can't. When I work for a company it doesn't become part of my Self, and I don't feel the need to spin its actions to make them look positive. If it's a company that 'does know evil' then get out, or get over it.

Can you elaborate on your claim that Dart designers optimized Delta Blue when porting it to Dart?

Here's the Dart code for Delta Blue: https://github.com/dart-lang/benchmark_harness/blob/master/e...

Here's the JavaScript code for Delta Blue: https://code.google.com/p/v8/source/browse/branches/bleeding...

I see a JS class for Constraint, and a Dart class for Constraint.

I see a JS class for Strength, and a Dart class for Strength.

This goes on and on. In fact, I see a top-level function for chainTest() in both JavaScript and Dart.

Remove OrderedCollection from JavaScript or add it to Dart, then compare. This extra level of indirection on every container is very costly in V8 and Ion. At least four of your coworkers are aware of this. They should have communicated it to you a long time ago.

> This extra level of indirection on every container is very costly in V8 and Ion.

It is very costly only if JIT is particularly bad at eliminating redundancies. Crankshaft is not and (I hope) neither is IonMonkey.

If you try removing it yourself from JavaScript version and replace every new OrderedCollection() with [], .add with .push, and so on then you will discover to your amazement that resulting code became 7-10% slower on V8 [try it, I am not joking :-)]

Now if you replace [] with new Array() then you get code that overall is 3-5% faster on V8. That is about how "costly" this indirection is.

Overall it seems that this is irrelevant in the large picture of things: Dart VM is around 195% of V8, dart2js is somewhere around 100%.

I do agree however that this OrderedCollection looks completely out of place and it is not clear to me why it appeared in the original JavaScript benchmark code at the first place. It is not idiomatic.

> you will discover to your amazement that resulting code became 7-10% slower on V8

I found both V8 and Ion to be >10% faster using array. I no longer have the results but IIRC it was 11% for V8 and 14% for Ion on i7 (ivy bridge). I moved remove() from OrderedCollection to Array prototype. Perhaps you made some other change.

> Overall it seems that this is irrelevant in the large picture of things: Dart VM is around 195% of V8,

There are 3 benchmarks. That is not enough data to say anything meaningful about Dart VM performance.

> dart2js is somewhere around 100%.

How can dart2js results be compared to the original JS if the data structures used are different? It makes no sense.

> Perhaps you made some other change.

I tried with both global remove and remove on the Array prototype.

V8 has recently improved DeltaBlue score by, I think, ~6% so it can be that before this improvement OrderedCollection overhead was more noticeable. (some of that improvement comes from tweaks in the inlining heuristics AFAIK).

> There are 3 benchmarks.

I was stating performance numbers for DeltaBlue only. Sorry for not being clear.

> How can dart2js results be compared to the original JS if the data structures used are different?

Substract 5%. dart2js is around 95%. Does it make sense now?

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