Tuesday Jun 02, 2009

Tuesday at JavaOne

It has been a busy day, of course. For those interested, I have posted the talk Brian Goetz and I gave on the Da Vinci Machine Project. We divided our attention between a “grand vision” of what VMs are and where they are going, and the exciting particulars of how invokedynamic and method handles work...[Read More]

Monday Jun 01, 2009

a beautiful life

Just about 24 hours ago, I was working on invokedynamic compilation in my hotel room with colleague Christian Thalinger. I have since learned that around that time, my dear grandmother, wise and loving to the end, slowly breathed her last and went to be with her Maker.

I suppose this is a strictly personal event, but as beautiful things deserve be shared, I would like to provide a glimpse of what this woman was like, in a photo of her and me taken 18 months ago.

[Read More]

at CommunityOne

Today’s talk at CommunityOne (San Francisco) about the Da Vinci Machine Project surveyed the history and status of the project to date. In the same spirit, I have updated the project page to include more pointers to recent talks, including my three talks this week at JavaOne. See you there!

Wednesday Apr 15, 2009

Lang.NET Symposium

I'm enjoying Microsoft's Lang.NET Symposium. Lars Bak just told us about the V8 JavaScript engine. As usual with his work, the virtues are overall simplicity, with a few careful choices about what to optimize. (The recipe is fixnums + stateful Self-like hidden classes + monomorphic inline caches + generational GC + simple JIT.) Here's the slide deck for my talk (up next) on new JVM features.

May 8 update: After the conference I enjoyed a video chat with Charles Torre of Microsoft Channel 9 about the Da Vinci Machine Project. Charles has posted a number of very good interviews from Lang.NET; check out those with Lars, Gilad, Anders, and Erik. Also, the Lang.NET organizers have posted synchronized slides and audio of the talks.

Saturday Mar 28, 2009

JSR 292 support in javac

In order to work with dynamic types, method handles, and invokedynamic I have made some provisional changes to javac as part of the Da Vinci Machine Project. (There is a full description for Project COIN; it's almost ready for publication, and I'll blog about that when I push it.) It is most desirable, of course, to program invokedynamic call sites as Java expressions, not just ASM code, and that's what those langtools patches are for.[Read More]

Wednesday Mar 25, 2009

PyCon VM summit

I was at the PyCon VM summit; it was great! There were about 20 talks (in the 10-20 minute range). Since "Sun" comes late in the alphabet, I had the pleasure of watching my fellow summiteers go first. When everybody was good and tired, I gave a presentation on the Da Vinci Machine Project. Here are some notes on a few of the other talks...[Read More]

Monday Feb 23, 2009

bloom filters in a nutshell

A Bloom filter is an array of M bits which is queried at K quasi-randomly selected positions pk (k < K). If all of the bits are set, then the query returns positive, indicating that someone has already visited the array, setting the bits at all the positions pk.

The filters are quite simple, but the math is a little slippery until you get the right grip on it. Here’s the way I like to grab it, presented in case it helps anyone else.

First of all, the bottom line: Size your Bloom filter to contain NK bits, plus an overhead of 44%. Put another way, for an error rate of ε, allocate lg(1/ε)·lg(e) bits for each key you intend your filter to hold.[Read More]

Monday Feb 16, 2009

simple Java linkage: an invokedynamic apéritif

JSR 292 is adding a fifth invocation instruction, invokedynamic. Like the other four invocation instructions, it is statically typed. What is new is that an invokedynamic instruction is dynamically linked under program control. In this blog, I will be giving “recipes” to demonstrate some of its applications. For today, here is a light aperitif showing how invokedynamic could be used to simulate the other invocation instructions. Caution: This blog post is for people who enjoy their bytecodes full strength and without mixers.[Read More]

Monday Dec 08, 2008

the date of Christmas comes more from Easter than the winter solstice

Christmas can be enjoyed as a much needed vacation day, a cheery cultural pageant, or a profound spiritual observation. For my part, I’ll take generous helpings of each. As it is a widely shared holiday, the first question is where to put it on the calendar. Thanks to Julius Caesar and his calendrical reforms, and to their enthusiastic adoption by the early Christian Church, we possess a clear date for Christmas.

But, why did the eventual consensus settle on December 25? Accounts vary, and it is a curious mystery. I think our date is equal parts historic reconstruction, arbitrary convention, and high art. [Read More]

Friday Nov 07, 2008

three software proverbs

Today I was late for lunch. As I walked to the cafeteria, pondering my work, this haiku came to me:
It will take more time:
If you touch it, it will break...
Software is wily.
Relaxing the syllable count limit in favor of word count gives each epigram a fuller and more independent expression:
Somehow it always takes longer:
If you touch it, it will break...
Software is a wily opponent.
Those latter three lines express the way I feel about my chosen craft.

I think of the middle line as Kempf’s Law of Software. It was a favorite expression of Jim Kempf, who was on the Sun Common Lisp team with me, long ago.

The last line expresses a stance I call “defensive programming”, which is what we programmers do when we take Murphy’'s Law seriously.

Wednesday Oct 01, 2008

the view from the Summit

Last week some Sun engineers and I invited our colleagues over to Sun Santa Clara to talk about the future of VMs and languages. We called the meeting the JVM Language Summit. It was a blast; I’d like to tell you why, and what I learned.

Pizza with extra MOP

Here are my top-level takeaways:

  • The invokedynamic design is sound, but the exposition needs more work.
  • The synergy of JSR 292 with Attila Szegedi’s MOP looks very promising.
  • Interface injection is going to be helpful to a lot of people, and it is not hard to implement (on top of method handles).
  • Tailcall and value types will never go away. We have to plan for them.
  • Unless we do this sort of innovation on the JVM, crucial multicore research will move elsewhere.
  • We have to do this again next year.
[Read More]

Tuesday Aug 26, 2008

Happy International Invokedynamic Day!

I have been working furiously this summer, patching the OpenJDK HotSpot JVM for the JSR 292 implementation of dynamic invocation.

In the wee hours of this morning, the JVM has for the first time processed a full bootstrap cycle for invokedynamic instructions, linking the constant pool entries, creating the reified call site object, finding and calling the per-class bootstrap method, linking the reified call site to a method handle, and then calling the linked call site 999 more times through the method handle, at full speed. The method names mentioned by the caller and the callee were different, though the signatures were the same. The linkage was done by random, hand-written Java code inside the bootstrap methdod.

The Email thread of the announcement is truly international, since Guillaume Laforge celebrated by sending virtual champagne.

The example code is included in the Email, and also posted (as a truly rebarbative test in a NetBeans project) with the patches. As for the JVM code, it only works on x86/32; the next step is to move the assembler code into the right files, and finish the support for x86/64 and SPARC.

Happy International Invokedynamic Day!

(And by a curious anagrammatic permutation of letters, it could also be International Davinci-Monkey Day. My co-workers, who watched me pounding on my keyboard all summer, claim to see some significance in this.)

Saturday May 31, 2008

with Android and Dalvik at Google I/O

Invited by some friends at Google, I went to Google I/O this week to find out about Android, and specifically their Java story. I went to a few talks and had some excellent chats with various colleagues.

Here are the top ten things I learned about Android and the Dalvik VM...[Read More]

Monday May 19, 2008

invokedynamic goes public

After a successful meeting at JavaOne, the JSR 292 EG (expert group) has published its EDR (early draft review) for the invokedynamic instruction. This draft will be updated from time to time (in response to your comments), until August 17, which is the end of the 90-day review period. Check it out!

Update: There are some good conversations going on about the EDR at the jvm-languages Google group. Here are some rough changes to the EDR I will be proposing in response; the EG may choose to make these changes (or something like them) official with an EDR update pushed through the JCP (Java Community Process).

Saturday May 10, 2008

the golden spike

In the Java cosmos we can reckon time in terms of JavaOne conferences. For programming languages on the JVM, the just-finished epoch has seen much progress, and the next epoch looks even better. Here is some of the progress that I am excited about, after bouncing around at JavaOne...

In other news, today (May 10th) is National Train Day. On this day 139 years ago, a ceremonial golden spike was driven at Promontory Summit, Utah, joining the Central Pacific and Union Pacific railways into a single transcontinental line. The continent was very suddenly smaller, because people, goods, and mail could be moved more quickly from coast to coast, a task which was previously done with wagons, horses, and boats. In the years leading up to this watershed event, two railroads were built, with great difficulty and ingenuity, from each coast, to meet at Promontory Summit.

There is a Promontory Summit and a golden spike in our future also... [Read More]

About

John R. Rose

Java maven, HotSpot developer, Mac user, Scheme refugee.

Once Sun and present Oracle engineer.

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