C++ annotations
http://www.icce.rug.nl/documents/cplusplus/


download PDF from
ftp://ftp.rug.nl/contrib/frank/documents/annotations/

- posted by Pop @ 4:47 PM

 
Virtual Construtor in C++
Problem: In message passing environment, Getting the right class instantiated on the receiving end.

Approach:
1. Tag each message class with a unique ID.
2. a global object pool consists of instance of each message class, i.e., each message class will rigister itself to this global object pool with an instance.
3. When getting a message, the tag is looked up and the new object will be created by CLONE (ing)

class Message {
public:
static Message* newMessage( const Message& );
virtual Message* clone() const {
 return new Message;  // or return new Message( *this );
}
...
};

Message* Message::newMessage( const Message &prototype ) {
return prototype.clone();
}

class myMessage {
public:
virtual Message* clone() const {
  return new myMessage; // or return new myMessage( *this );
}
...

All you need to do is create an object of each class in the Message hierarchy and put them in a container class which can be searched.  When
you receive a message, get the type ID and iterate on the container of Message objects until you find a match.  Use that object as the argument to
newMessage().

void messageHandler( const messageStream &msg )
{
...
msg >> messageType;
Message* prototype = objectContainer.find( messageType );
Message* currentMsg = Message::newMessage( prototype );
msg >> ¤tMsg;
...
}
};

- posted by Pop @ 7:30 AM

 
Reading List
http://theory.stanford.edu/~Erajeev/cs361.html#Readings

Lectures 1 and 2 - Should tables be sorted?
Should tables be sorted

Table Should be sorted (on random access machines)

Lectures 3 and 4 - Hashing: Universal and Perfect
Denial of Service via Algorithm Complexity Attack

Store a Sparse Table with O(1) Worst Case Access Time

Lecture 5 - Amortization and List Update Problem
Amortized Efficiency of List Update and Paging Rules

Lecture 6 - Disjoint Sets and Union-Find
Lectures 7 and 8 - Competitive Analysis and Paging
Amortized Efficiency of List Update and Paging Rules


Lectures 9 and 10 - Randomized Online Algorithms
Lecture 11 - Self-Adjusting Search Trees
Lecture 12 - Treaps: Randomized Search Trees
Lecture 13 - Skip Lists
Lecture 14 (part 1) - Caching Queues
Lecture 14 (part 2) - Self-Adjusting and Fibonacci Heaps
Lecture 15 -- Hashing for Massive/Streaming Data
Distinct Sampling for Highly-Accurate Answers to Distinct Value Queries and Event Reports. P. Gibbons. VLDB 2001.
STREAM http://www-db.stanford.edu/stream/demohelp/

- posted by Pop @ 8:49 PM

 
Memory Model in multithreaded environment: broken double check locking
1. "The double-checked locking is broken" declaration
http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html

Quoted:

Double-Checked Locking:
1. an efficient method for implementing lazy initialization in a multithreaded environment. (Mostly used in Singleton pattern)

Status:
1. In Java, not work reliably in a platform independent way
2. In C++, depends on the memory model of the processor, the reorderings performed by the compiler and the interaction between the compiler and the synchronization library. Explicit memory barriers can be used to make it work in C++, but these barriers are not available in Java.

2. Discussing in memory model in multithreaded C++
http://www.hpl.hp.com/personal/Hans_Boehm/c++mm/mmissues.pdf
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1876.pdf

Quoted:
problem:
1. C++ standard doesn't mention threads.
2. Threads added via libraries (e.g. pthreads).
3. Compiler mostly unaware of threads.
4. Synchronization calls treated as opaque.

Proposed Solution:
1. Atomic operations library
- load Atomically read the value of the integer.
- store Atomically replace the value of the integer.
- fetch and add Atomically add a value to the integer.
- store with release ordering semantics Atomically replace the value of the integer, and ensure that all prior memory operations executed by this thread become visible to other threads before the update.
- load with acquire ordering semantics Atomically load the value of the integer, and ensure that all later memory operations performed by this thread become visible after the load.

2. Memory model based on sequential consistency to avoid data race
- requires sequential consistency for ordinary variable accesses, but efectively allows reordering of atomic variable accesses when determining the existence of a data race, i.e. it tries to adapt the original solution.

3. Java approach
- sandbox execution of untrusted code
- ensure that no load of a shared pointer can ever result in a pointer to an object that was constructed with a different type. (This requirement will avoid the concurrent read-write confliction to a shared object)


3. Impact
an unavoidable impact on compiler optimization.7 Some currently common compiler optimizations need to be adapted to ensure thread safety. But this also reinforces
the urgency for thread support in C++
- posted by Pop @ 8:31 AM 0 comments

 
csh script examples
http://quong.best.vwh.net/shellin20/#LtohTOCentry-21

#! /bin/sh
URL=$1
I=$2
if [ x$URL = x ]; then
URL=localhost:9000
fi

if [ x$I = x ]; then
I=1
fi
while [ $I != 0 ]; do
I=$(( I-1 ))
linux2.4-glibc2.3-x86/dynamic_debug/test -u $URL -a 200K -t sync -f dummy -d get -i 1;

linux2.4-glibc2.3-x86/dynamic_debug/test -u $URL -a 2M -t sync -f dummy -d get -i 1;
done
- posted by Pop @ 7:00 PM

 
XPath pattern

From http://www.w3.org/TR/xslt
section 5

Here are some examples of patterns:

• para matches any para element

• * matches any element

• chapter|appendix matches any chapter element and any appendix element

• olist/item matches any item element with an olist parent

• appendix//para matches any para element with an appendix ancestor element

• / matches the root node

• text() matches any text node

• processing-instruction() matches any processing instruction

• node() matches any node other than an attribute node and the root node

• id("W11") matches the element with unique ID W11

• para[1] matches any para element that is the first para child element of its parent

• *[position()=1 and self::para] matches any para element that is the first child element of its parent

• para[last()=1] matches any para element that is the only para child element of its parent

• items/item[position()>1] matches any item element that has a items parent and that is not the first item child of its parent

• item[position() mod 2 = 1] would be true for any item element that is an odd-numbered item child of its parent.

• div[@class="appendix"]//p matches any p element with a div ancestor element that has a class attribute with value appendix

• @class matches any class attribute (not any element that has a class attribute)

• @* matches any attribute

- posted by Pop @ 4:37 PM

 
XML schema validation in Java and schema design

- posted by Pop @ 9:12 AM

 
XML Schema Design [ Best Practice ]

- posted by Pop @ 9:18 AM

 
Stay Hungry, Stay Foolish
http://news-service.stanford.edu/news/2005/june15/jobs-061505
This is the text of the Commencement address by Steve Jobs, CEO of Apple Computer and of Pixar Animation Studios, delivered on June 12, 2005.
- posted by Pop @ 3:01 PM