Digital serialization of "I"

Hybrid Type Inference support in SpiderMonkey

2012-02-05T00:46:00.000-08:00

Few days ago, Firefox prompted me with the pop up window to download and update itself with its recently released version 9.0. I got curious to know about what is new in this version and hence went to read the release notes from Mozilla.

In a very small duration of time, I got delighted with the fact that this release has JavaScript performance improvements as one of the major highlights. I got fascinated with performance improvement claims (~30%) in JavaScript execution. Upon further digging in, my curiosity kept on increasing, when I started reading about its “Hybrid Type Inference” support in its JavaScript engine “SpiderMonkey”. After studying in detail, it became pretty clear that this is a very significant change in execution strategy for JavaScript and has the potential to set a new trend altogether.

JavaScript as a language has established itself as the de-facto language for client side programming in the world of web development. Its vast popularity across the globe has generated immense interest of global developer’s community and many corporates in this language. This has created a very healthy competition amongst different vendors who want to dominate in the browser war. Google’s Chrome was the first one, which actually introduced a lot many new radical changes in its V8 engine, which forked huge performance improvements in the language execution.

One of the most important was the introduction of JIT compilation in JavaScript. Use of JIT compilation rather than interpretation has generated huge performance benefits. Still the language takes a back seat when you compare the performance of the language with some of the other established languages which use JIT compilation like Java, C# etc.

Where is the gap?

This gap is mostly because JavaScript provides a lot of freedom to its developers. Execution engine pays the cost of this freedom. What kind of freedom, we are talking about here? This freedom is primarily the freedom of developers to treat any variable as any type and the freedom of type extension at runtime.

Let’s get into the detail of the first type of freedom (Typeless nature of language): Languages like JavaScript don’t have the notion of static type, which becomes a bottleneck in generating a very efficient machine code. Let’s consider a very simple case of adding two integer variables and assign the sum to a third variable. If the compiler has to generate a code, where in it has no idea that it is a sum operation of integers then it will emit code which should be able to handle addition of any two types of variables be it int, float, string etc. But assume when the compiler has the knowledge of the types of the variables, which are going to be added then in such cases it become very easy and straightforward for the compiler to generate machine code, which can handle integer addition and the sum results into an integer.

Pure static analysis for Type inference a rescue?

It becomes quite clear that to achieve the performance of languages like Java, C#, generation of Type specific code is quite important. Unfortunately, for wild language like JavaScript, this is not a straightforward task. One way to achieve this is by performing purely static analysis of the code. But the challenge here is that because of the openness of the language, any pure static analysis for inferring Types becomes so computationally heavy that it does not pay for the performance improvements, which it brings in. Also, because the language is Type less and supports prototype for object extension at runtime, it becomes almost impossible for any static Type analyzer to emit out precise code with all type variants. And not generating code for all possible Types is like changing the expected behavior of the code, which by no means can be regarded as a sound strategy.

Here comes the very interesting strategy for type inference implemented in SpiderMonkey shipped with firefox version 9. It supports a hybrid approach to achieve Type inference. This strategy is an outcome of the acceptance of following facts explained earlier.

1. Compiled machine code, which does not have Type notion can’t be as efficient as the one, which gets generated after Type inference.

2. For any pure static analyzer for Type inference, it is quite impossible to do justice on all the fronts:

a. Sound code: The emitted code should be able to take care of all possible Types and object extension at runtime.

b. Cost of analysis: The analyzer should not be very computationally heavy, otherwise the static analysis offsets the performance benefits at the runtime.

3. If we also take into consideration the usage pattern of JavaScript code for many different websites, then it can be realized that many of the times, we end up loading huge amount of JavaScript code for the website but only end up using a small fraction of it.

The Hybrid approach is nothing but to account for only a subset of Types during static analysis and the ones, which are not accounted during the static Type inference analysis, there should be a way to catch those cases dynamically. This approach not only generates the optimized machine code for the most expected Types in the code by doing static Type inference, but also keeps a provision to catch dynamically at the run time for all those cases, which do not score very high as a candidate for possible Type during static analysis.

Of course this approach is not so simple in implementation as it has to provide the capability of dynamically catching the uncommon cases. If you combine the object’s Type extension capability in the language with the earlier challenge then it actually becomes quite complicated scenario. There are many things, which need to be considered while having such a flexible strategy.

1. Precise and efficient static analyzer.

2. Capability to dynamically catch cases which are not handled through the static analyzer.

3. Dynamically catching the uncommon cases also comes with a cost, which is not there in the Typed languages. To reduce this further, have provision of supplemental analysis like overflow scenario, definite properties inside objects etc.

4. Recompilation of the code at the runtime to handle the case where in a new Type is identified at the runtime, which was not taken into consideration by the static analyzer.

5. More complicated memory management: Type inference by static analyzer and capability to recompile the code while it is running also brings in additional overhead to memory management. The execution engine needs to ensure that it is only keeping the relevant compiled code in memory and the garbage collector is collecting the rest.

To handle these things, Firefox has not only changed its JavaScript engine (SpiderMonkey) but also had to made relevant changes in its JIT compiler (JaegerMonkey). If you go into the details of the implementation there are so many things being introduced like sematic triggers, Type constraints, Type barriers etc… But yes these core changes have definitely justified the performance benefits, which it has created. I can’t even imaging, how many million man-hours are being saved by enhancing the performance of the most popular language for client side web development. Hats off to those engineers involved in this improvement.

Here are some of the relevant links related to this topic:

http://www.mozilla.org/en-US/firefox/9.0/releasenotes/

http://people.mozilla.org/~lmesa/ti-draft.pdf

http://arstechnica.com/open-source/news/2011/12/firefox-9-slinks-onto-the-scene-with-fancy-javascript-optimizations.ars

http://labs.oracle.com/self/papers/pics.html

Signing off for this time with a request to provide your fruitful comments…

--RBK

MapReduce v/s SQL

2012-01-26T01:03:00.000-08:00

I was exposed to the MapReduce paradigm couple of years ago and am in touch with the open source implementation of MapReduce framework (Hadoop) since then. We started to play with Hadoop actively to understand the pros and cons of the framework and as of today we have considerably progressed by building our new platform backed by this powerful distributed computing framework.

During this whole journey, we encountered many challenges and questions. One of the most frequent query was why not SQL based systems and why Hadoop? After going through various discussions, technical articles and my own exposure to this system, I thought of sharing my own experience around this very frequent query originating from different development community.

The concept of MapReduce was actually brought in to solve the scale problem when you are dealing with huge amount of data, which nowadays is not a problem that exists only for big corporate houses (like Google, Microsoft etc.). With the bloat of information everywhere, this problem of dealing with huge data set has become a more common problem than earlier. Most of the times people try to solve it with the conventional systems like SQL. Many of the places, it has been successful up to some extent, but beyond a threshold, it becomes really very challenging to tackle this problem with those conventional systems. There are many reasons of this challenge.

1. Unstructured data processing: SQL systems are optimized to deal with structured data. The whole concept of relational databases is based on the notion of relational schema to store information, which becomes a challenging when you are dealing with unstructured data. In such cases you end up retro fitting your information in a tight schema, which creates challenge while digging out insight from the data.

2. Control on processing steps: SQL mostly is a language, which is declarative in nature, and when you use SQL for querying information, you pass on your interest in result and the data sources from where this information can be retrieved. The actual details of how to get to the result still lies under the control of query processing engine. So, you are left with nothing (Most of the time you can only pass on some clue/hint to the engine to influence its strategy of processing), but to rely upon the genius of processing engine to provide you the data through optimal processing.

3. Scale (out v/s up): Conventional systems like relational databases are designed to work on monolithic systems rather than distributed clusters. This imposes the constraint that while addressing the scale issue, you will end up buying costlier hardware. One thing worth noting here is that cost of the hardware does not increase linearly, meaning the cost of one machine having 5 times power than a standard machine is more than 5 times costlier than the standard machine. Because of this equation, it makes more sense to address the scale challenge horizontally than vertically. That means if you build framework where in you can scale by just adding more no. of machines, it makes more sense. Of course adding more machines comes with an overhead of more co-ordination requirements. For which if you have at your luxury a framework like Hadoop, then it can be a smart move to approach for scale out using such frameworks.

4. Offline v/s online processing: The original requirement because of which the MapReduce framework originated was around processing huge amount of data without caring about items like realtime processing, transaction support etc. Hence these systems are more optimized for offline processing rather than realtime processing of data. Though there are many other technologies, which are trying to address these pieces as well, but still as of today, in the heart of the framework, it is fundamentally a offline distributed processing framework.

5. Raw talent v/s conventional wisdom: Relational database systems have existed in the industry for quite a few years and it has catered to the need of its age very successfully. These successful years of SQL adoption in the s/w industry has produced a lot of experts around that technology. So, when you are using SQL based systems, you have the luxury to have these expert advices. On the contrary, in the MapReduce world, the thought process is quite different and during your initial days of its adoption, it is very likely that you may end up designing your system in the relational way even though underlying you tend to use these new frameworks. Design and thought process in MapReduce requires a raw thought process, and the moment you try to retrofit this with conventional thought process of how to build your stack thinking about entities and its relationships, you debar yourself from gaining the juice of MapReduce framework.

Conclusion

This post certainly does not cover each and every aspect of both the systems, but IMHO, it provides you some data point to think about while you are planning to build your stack around these technologies. Obviously, the intent of the post is not to prove anything, but to dig out different relevant points around these technologies. For a given requirement, it is even possible (and it is not very remote possibility in many of the cases) that you end up building your stack with a marriage of both these technologies.

Signing off for right now with a request to provide your fruitful comments…

--RBK

Tanhai...

2012-01-24T08:49:00.000-08:00

Har bita lamha apni ek tasveer liye aata hai,
Mujhe meri tanhai mein dara jata hai.
Mujhe khud se nahin apni tanhai se ummid hoti hai,
Aur ek ajeeb si bechaini uski taqdeer hoti hai.

Tanhai mujhse sach kahne ko kahti hai,
Kabhi kabhi to jid karne lagti hai,
Main use jhoothla nahin pata hoon,
Chah kar bhi kabhi jeet nahin pata hoon.

Main khud se baat karna chahta hoon,
Kuch paheliyon ka hal dhoondhna chahta hoon.
Par tanhai ko mujh pe bharosa nahin hai,
aur ab to mujhko bhi yakeen yahi hai.

Band aankhon mein roshni jab chamkti hai,
Sannate mein kisi ki aahat jab khatkti hai.
Tab har baar meri tanhai mujhse pahle jagti hai,
Aur mujhe jagakar badi bedard si hansti hai.

Wo mera kuch nahin kar payegi ye janta hoon,
Per phir bhi achanak se apne ko dara hua pata hoon.
Aur khusi hoti hai ki kabhi to main sach se darta hoon,
Aur in sab ke baad bhi usse baat karne ko tadpta hoon.

Ek khwahish hai kabhi to wo mujhe raasta bataye
Uske jaisa kyun nahin hoon, ye samjhaye.
Lekin poochne ke pahle hi phir se dar jata hoon,
Aur phir se apne aap ko wahin tanha pata hoon.

-- RBK

“Kyun hai” – My first poem

2009-07-19T01:10:00.001-07:00

Har saans mein ehsaash kyun hai?
Har ehshaash mein ek pyas kyun hai?

Har pyas mein milawat kyun hai?
Har dard mein ek chahat kyun hai?
Har chahat mein ek dikhawat kyun hai?
Har dikhawat mein ek banawat kyun hai?

Har lamha itna bikhra kyun hai?
Har aaj itna mohtaaj kyun hai?
Har chehra itna suna kyun hai?
Har roj mujhe jina hi kyun hai?

Sochta hoon sochna hi kyun hai?
Na sochna hi achha kyun hai?

Har khwahis itni jiddi kyun hai?
Har aadmi itna piddi kyun hai?
Har raat itni chhoti kyun hai?
Har din itna bhaari kyun hai?

Sochta hoon ek aadhar dhoondh loon
Jine ka sansaar dhoodh loon
Par us sansaar ki jaroorat kyun hai

Sochta hoon sab mithya hai yahan pe
Per in sab mein itni haqeeqat kyun hai.

--RBK

Many many congratulations “Raza and Mubeen”

2009-07-13T09:22:00.001-07:00

With the title of the blog, most of the readers would have guessed that probably its a congratulation to a newly wed couple. you are right and i am on the way to return journey from Hyderabad to Bangalore and just trying to recollect the moments which I spent this weekend. There are so many sweet memories attached with the trip and I would like to share it with you. These memories make it a memorable one. Some of the main reasons are:

It was wedding of one of my very good friend (Raza)
First time i was attending a Muslim wedding and I was very excited for it.
The day of marriage was also my birthday :)
I met with many old friends and spending time with them was real fun.

What else do you want to achieve during a normal weekend.

I left from my office on Friday evening then met one of my very old fiend on station. It was his first day in office after passing out from IIMb. we sat in the train and my phone started ringing from 11 P.M. onwards. Many of the people who were knowing that i was travelling that night were wishing before time as they were worried about what if i am out of the signal coverage. So, first time i celebrated my birthday inside a Indian Railways coach.

Next morning we were in the city with which i have a lots of memories as this is the city from where my career started. Then we met with the groom and here we were a little bit disappointed to see the tummy of the groom (Raza i am sorry but its a truth). Next with friends i moved to a nearby shopping mall (GVK 1) and did some shopping for my birthday. Celebrated the birthday with the pastries from Karachi bakery and then in the evening finally reached the place where the marriage was supposed to take place. i was thrilled as i wanted to know the way it goes on and i actually found it very exciting. We met with the boy, congratulated him and then finally had that awesome biryani which was the crux of all things. Thanks raza for the awesome biryani. I suggest you to open a restaurant with the same caterer.

The very next day it was a fun time with friends, met with raza and bhabhi. I along with Vineet and Himanshu did lots of masti and the finally i am returning back from Hyderabad to Bangalore. When i recollect the moments many of the things are still there which make me either laugh/smile like:

Joke by Himanshu (Because I find that i have some responsibility towards the society, I cann’t publish that here, but it was a killer one :) ).
Dhokala, Raj kachauri and masala milk of Tiwari. I miss it like anything in Bangalore.

Wish you all the best Raza and Mubeen in the new life.

Thank you sir

2009-07-10T08:28:00.001-07:00

Today was a great day for me and this blog will explain it how.
We had a party time from our company and we went to a resort (Leo meridian) outside the city for having some dance practice from john britto gang. Every thing there was cool and we all tried (because I think it was only a try not a dance) to dance for almost 4-5 hrs and then came back home. While coming back home I met a person who is in Indian military. I must say you here that this was not planned. We just met him and I was really very much impressed by his thoughts he shared with us during that small meet. I feel that it should be a valuable thing to share those with my friends and that’s why I am putting all the thoughts in this blog.

We all were returning from the dance class in which all the dances were of western nature or better to say non-indian kinda. When we let him know about this I feel that he did not feel very great about it. Though it does not mean he was against these things but still he wanted it to happen some other way. Then he told us the way he feels and just with in 15 minutes he put his thoughts before us and here are those precious ones…
First of all being a military person he told us the kind of invasion a country can have. He told that there can be 3 types of invasion in this world.
1. Military Invasion: which is the least dangerous in its impact as the asset lost and things destroyed can be recovered and rebuilt if the nation has a good will power for it. Its impact goes out in the least time once the war is over which we can justify by many such events which happened in history.
2. Economic Invasion: These is the 2nd type of invasion whose impact is worse than the first one and in this one you never get a direct feel of the attack being taking place and after some time you realize about your inability which automatically generates as an aftereffect of this. Its impact is more lasting and the recovery takes time.
3. Cultural Invasion: This is the 3rd in its kind and most brutal in its impact as the recovery is almost impossible. In this you even don’t feel that some thing wrong is going on somewhere, rather you feel that there are something sweet going on. And you get a feel of things going positively with a rocking speed. And in most of the cases while persuading that speed you forget your roots and your own culture and finally when the impact appears bare faced then you are not in a position to recover. As mentioned here this one is the most deadly due to its impact and the hidden nature of attack.
The person who was putting these thoughts said to us that we (actually most of us, mostly young generation) are under attack of the 3rd kind of invasion and as per its nature we are not able to feel it rather we are feeling better. His main concern was that its not bad in tasting things which others have and others do but there should not be a blind aping of things.
He even quoted the starting days of this attack when Englishmen used to distribute packets of tea free of cost during his grandpa’s days and we gradually lost our own sarbat, lassi and sattu pani.

It was really a great a talk with that gentleman and I would like to salute his way of thinking and attitude. He did not preach us to live our life differently than what we are doing right now, but he just cautioned and requested us to check our roots time to time.

I salute his thoughts and I hope that his concern will not go in waste. Thanks a lot sir for sharing such valuable thoughts.

[This is a post from my old blog. On public demand I am re-posting it ;) Please refer today as december 3 2006.]

In the lap of nature

2009-07-07T11:39:00.001-07:00

“Reading about nature is fine, but if a person walks in the woods and listens carefully, he can learn more than what is in books, for they speak with the voice of God.”

I almost heard this voice during my trip to Coimbatore. It was really an awesome experience to be there. It was a random trip which was planned at the eleventh hour. I, mummy and Vikas went to coimbatore to meet my youngest sister.

We only stayed there for one and half days but the places where we visited and the fun which we had was awesome. First we started with a visit to a temple called Dhyanalinga, which was so soothing in its own. It is a Yogic temple which is more a meditation center. We had the first time experience to take a bath in the kund where the shivling was immersed. To worship the shivling standing inside water was a different experience altogether.

The main temple was a large ellipsoidal dome with the lingam (more than 10 ft in height) in the center. People who were visiting the temple were sitting around that lingam and doing meditation for some time.

After the temple we had lots of fun during the lunch time and then we roamed other places around the city.

In the night we went to a restaurant in the city where we ordered family dosa which was a unique experience in its own. You can imagine the uniqueness about it by looking at the photographs.

We enjoyed the food a lot and actually we gave prizes as ranks to people who played key role in finishing the child Anakonda aka THE DOSA.

Next day we had a comparatively peaceful day when I got more time to observe nature more closely. I was so fascinated with the beauty of nature that i could not stop myself composing and singing these lines

आसमां कह रहा है जमीं से! बादलों को छुओगे कैसे !!

पत्तियां हिल रही हैं ऐसे ! ज़िन्दगी जी रही हो जैसे !!

बादल भी उतरने को आतुर ! चुमते हो पहाडों को जैसे !!

झरने भी बहे जा रहे हैं ! गीत गता कोई बैठे बैठे!!

अब चली है वही फिर बयार! जैसे सब को सिखाती हो प्यार !!

पछियों की ध्वनि छा रही है ! दिल में वीणा बजी हो जैसे !!

ज़िन्दगी तो बसी है यहीं पे ! दिल मचलता है जीने को जैसे !!

Many many thanks to Archu and her friends to make all this real.

निष्कर्ष

2009-02-06T13:41:00.001-08:00

This is one of the many poems written by my younger sister. I really love to read her poems. Whenever I go through her poems, I feel so proud of her.

आज कुछ पल हैं, अपने साथ होने को,
जीवन की रफ़्तार में अपनी गति समझने को,
मैं कठघरे में हूँ, उस मैं के आगे,
जो कभी मेरा आत्मीय था,
अब उसका होना ऐसे पलों पर आश्रित था.

मेरे दृश्य पटल पर सारा अतीत चलचित्र है,
अचंभित सी वहां अपनी मौजूदगी देखती हूँ,
दृश्य पर दृश्य अपने अस्तित्व की तलाश है,
पर अपनी पहचान धुधली नज़र आती है,
क्यूँ अपनी जय पराजय में मैं स्वयम दर्शक मात्र हूँ ?

जिंदगी चंद दस्तावेजों की ही मुहताज क्यूँ है?
क्या मेरा समर्पण मेरी जीत नहीं है ?
प्राणवान होना हास्य पैर नहीं स्वाश पर निर्भर है,
तो हँसने की ही चाह क्यूँ करती हूँ मैं?
क्या मेरे रुदन में कोई सार्थकता नहीं है?

क्यूँ अपनी नीयति को अपनाना नहीं आता मुझे ?
वो जो मेरे होने से भी अर्थहीन है,
उसके होने में अपने अर्थ की तलाश कैसी?
शायद इन सवालों के जबाब दूसरे सवाल ही हैं
और निष्कर्ष की चाह व्यथा को आमंत्रण.

-- वंदना वशिष्ठ

My first blog

2009-02-06T13:18:00.001-08:00

Hi All,

This is going to be my first blog entry. It does not mean that i never blogged before, but this time i thought of giving blogging a new try. Hence I deleted my previous blog and recreated with the same url from the scratch.

As the description of the blog itself says, the blog is about

“Digital Serialization of my realization of the world.”

Hence I will post about anything what I feel to share with myself and my readers. Lets wish and hope that this effort has a long lasting effect.