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[#1010274] Experimental Patch of Doom!

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Date:
2008-02-10 17:16
Priority:
3
State:
Open
Submitted by:
Jon Hanna (talliesin)
Assigned to:
Nobody (None)
Category:
Group:
Resolution:
None
 
Summary:
Experimental Patch of Doom!

Detailed description
Okay, nobody try this on production code, there's still a lot of checking for me to do on things.

Still this should add:

CommandBehavior.SequentialAccess support.

As-needed loading of DataReader objects.

Correction of connections left in a corrupt state by earlier errors (particularly with regard to the Thread.Abort() issue reported by AS).

Testing notes:

1. The connection-correct currently only works of Protocol Version 3, trying this with Protocol Version 2 is likely to be a mess, even when there aren't any errors to correct for.

2. The change in DataReader access should hopefully improve performance for very large resultsets. Performance measurements should measure both the time to first successful Read() as well as the time to complete a full operation, since this is where the biggest gain should hopefully have been made, and it can be very important in some applications.

3. In the case reported by AS as well as there being issues with subsequent queries by the client in question, there were also orphaned postgres.exe processes. Therefore attempts to find errors it doesn't handle should look for such orphaned instances, as well as for correct recovery as seen on the client.

Followup

Message
Date: 2008-03-12 12:26
Sender: Andreas Schönebeck

A bit off-topic now... But Jon asked for it :-)

I feel lucky, that I don't have to write ASP.NET stuff yet. Anyway, I am working with Npgsql2 beta 2 all the time during development, and I'm trying to show my employer and our customers, that there are excellent alternatives for SQL Server around, which is what they normally use.

Firstly implemented generic database code using System.Data.Common and we now support Npgsql (the good), SqlClient (the bad), Odbc (the ugly) and SQLite (the friendly). Everything works well but for Npgsql, which is just a bit unstable. That's the reason, we're not using it yet in demo's and ask customers to use SQL Server, keeping quiet about PostgreSQL. But using SQL Server means, they have to pay for a DBMS as well and that increases their net-cost. I'd really like to start pushing PostgreSQL, but at the moment my subconscious tells me not to.

Now back to patching... To be able to work with Npgsql2 beta 2 at all in a sort of stable manner, I applied a little self made patch I've done on the first day of playing with it. It's there for months now and increased stability considerably. It's basically just catching all exceptions in ExecuteCommand (not just IOExceptions). I had to test for NULL in the connector pool as well, which gets corrupted with NULLs during ClearPool...(). Here it goes for everyone who wants to have a laugh:

Index: D:/Quellen/MoveMap CS/trunk/Npgsql/Npgsql/NpgsqlCommand.cs
===================================================================
--- D:/Quellen/MoveMap CS/trunk/Npgsql/Npgsql/NpgsqlCommand.cs (revision 96)
+++ D:/Quellen/MoveMap CS/trunk/Npgsql/Npgsql/NpgsqlCommand.cs (revision 97)
@@ -1395,6 +1395,9 @@
ClearPoolAndThrowException(e);
}

+ catch (Exception e) {
+ ClearPoolAndThrowException(e);
+ }
}

private void SetCommandTimeout()
Index: D:/Quellen/MoveMap CS/trunk/Npgsql/Npgsql/NpgsqlConnectorPool.cs
===================================================================
--- D:/Quellen/MoveMap CS/trunk/Npgsql/Npgsql/NpgsqlConnectorPool.cs (revision 96)
+++ D:/Quellen/MoveMap CS/trunk/Npgsql/Npgsql/NpgsqlConnectorPool.cs (revision 97)
@@ -81,6 +81,10 @@
{
foreach (ConnectorQueue Queue in PooledConnectors.Values)
{
+ if (Queue == null) {
+ continue;
+ }
+
if (Queue.Count > 0)
{
if (Queue.Count + Queue.UseCount > Queue.MinPoolSize)


Cheers,
Andreas
Date: 2008-03-11 11:37
Sender: Jon Hanna

"BTW: Yes, I still know killing threads with Thread.Abort() is
bad. But its there in the framework and people and me will use
it :-)."

Totally agree. Not to mention how often people don't even realise they're calling it (ASP.NET coders call Response.End() and we never worry that doing so calls Thread.Abort()).

If we can get it to handle really contrived cases with threads being killed all over the place, then we can be confident we'll deal with anything that happens in the wild. Your writing very tough test-scenario code means we can have a very strong library.

I'll get to work on your examples here soon.

How's it going apart from that for you?
Date: 2008-03-11 10:45
Sender: Andreas Schönebeck

Hi Jon,

I found more exceptions, when extending my test case to run multiple threads at the same time. Now there are 5 threads started at the same time and stopped via Thread.Abort() after random timeouts. This is done ten times in sequence. Occasionally I get this type of output with an exception (Not Seekable Exception):

[Main] Starting Thread [2.0].
[Main] Starting Thread [2.1].
[Main] Starting Thread [2.2].
[Main] Starting Thread [2.3].
[Main] Starting Thread [2.4].
[Main] Aborting Thread [2.0].
[2.0] Unhandled exception caught after 19482 rows (System.NotSupportedException): Dieser Stream unterstützt keine Suchvorgänge.
[Main] Aborting Thread [2.1].
[2.1] Thread aborted after 12181 rows.
[Main] Aborting Thread [2.2].
[2.2] Thread aborted after 0 rows.
[Main] Aborting Thread [2.3].
[2.3] Thread aborted after 27590 rows.
[Main] Aborting Thread [2.4].
[Main] Waiting for Threads to finish.
[2.4] Thread aborted after 3981 rows.


And as well occasionally this type of exception (Not Supported Exception):

[Main] Starting Thread [8.0].
[Main] Starting Thread [8.1].
[Main] Starting Thread [8.2].
[Main] Starting Thread [8.3].
[Main] Starting Thread [8.4].
[Main] Aborting Thread [8.0].
[Main] Aborting Thread [8.1].
[8.0] Thread aborted after 6206 rows.
[8.1] Thread aborted after 0 rows.
[Main] Aborting Thread [8.2].
[Main] Aborting Thread [8.3].
[8.3] Thread aborted after 0 rows.
[8.2] Unhandled exception caught after 2300 rows (System.NotSupportedException): Backend sent unrecognized response type:
[Main] Aborting Thread [8.4].
[Main] Waiting for Threads to finish.
[8.4] Thread aborted after 12042 rows.


A typical state of Postgres (8.3, Vista), which can be seen via SELECT * FROM pg_stat_activity, just after the program finishes and is showing "Press any key...", can be seen here:

16438;"gps";5532;10;"postgres";"SELECT * FROM Original";f;"2008-03-11 11:11:28.302+01";"2008-03-11 11:11:28.302+01";"2008-03-11 11:11:28.224+01";"::1";49644
16438;"gps";5928;10;"postgres";"SELECT * FROM Original";f;"2008-03-11 11:11:28.365+01";"2008-03-11 11:11:28.365+01";"2008-03-11 11:11:28.349+01";"::1";49645
16438;"gps";4924;10;"postgres";"SELECT * FROM pg_stat_activity;";f;"2008-03-11 11:12:03.521+01";"2008-03-11 11:12:03.521+01";"2008-03-11 11:10:07.474+01";"127.0.0.1";49641
16438;"gps";4476;10;"postgres";"<IDLE>";f;"";"2008-03-11 11:12:02.084+01";"2008-03-11 11:11:54.287+01";"::1";49691
16438;"gps";4660;10;"postgres";"<IDLE>";f;"";"2008-03-11 11:12:00.724+01";"2008-03-11 11:11:54.615+01";"::1";49692
16438;"gps";4512;10;"postgres";"<IDLE>";f;"";"2008-03-11 11:12:00.834+01";"2008-03-11 11:11:55.505+01";"::1";49694
16438;"gps";4644;10;"postgres";"<IDLE>";f;"";"2008-03-11 11:12:02.021+01";"2008-03-11 11:11:55.115+01";"::1";49693
16438;"gps";3544;10;"postgres";"<IDLE>";f;"";"2008-03-11 11:12:02.38+01";"2008-03-11 11:11:56.084+01";"::1";49695

There are five <idle> connections in the Npgsql connection pool, which is what should be there, because we needed a maximum of five connections simultaniously during the program run. But there are still two Orphaned <SELECT * FROM original> statements which could not handle the Thread.Abort calls graciously.

And now, here is my modified multithreaded test case. I tried to keep it simple, but its getting a bit more complex now. I'm sorry, that I have to post the code inline like this, but I can't find an upload button. Here it goes:

using System;
using System.Data.Common;
using System.Threading;
using Npgsql;

class Program
{
private const int MinTimeout = 10;
private const int MaxTimeout = 500;

public static void Main(string[] args)
{
Random rnd = new Random();
for (int i = 0; i < 10; i++) {
RunTestAbort(i.ToString(), new int[] {
rnd.Next(MinTimeout, MaxTimeout),
rnd.Next(MinTimeout, MaxTimeout),
rnd.Next(MinTimeout, MaxTimeout),
rnd.Next(MinTimeout, MaxTimeout),
rnd.Next(MinTimeout, MaxTimeout),
});
}
RunTestAbort(10.ToString(), new int[] {0, 0, 0, 0, 0});

Console.Write("Press any key to continue . . . ");
Console.ReadKey(true);
}

public static void RunTestAbort(string id, int[] sleeps)
{
Console.WriteLine();
// Create ConnectionString
NpgsqlConnectionStringBuilder csb = new NpgsqlConnectionStringBuilder();
csb.Host = "localhost";
csb.Database = "gps";
csb.UserName = "postgres";
csb.Password = "postgres";
// Start concurrent threads
Thread[] threads = new Thread[sleeps.Length];
for (int i = 0; i < threads.Length; ++i) {
StatementThreadParameters p = new StatementThreadParameters(
id + "." + i.ToString(),
csb.ConnectionString,
"SELECT * FROM Original"
);
threads[i] = new Thread(StatementThreadFunc);
Console.WriteLine("[Main] Starting Thread [{0}].", id + "." + i.ToString());
threads[i].Start(p);
}
// Sleep and Abort Threads
for (int i = 0; i < threads.Length; ++i) {
if (sleeps[i] != 0) {
Thread.Sleep(sleeps[i]);
Console.WriteLine("[Main] Aborting Thread [{0}].", id + "." + i.ToString());
threads[i].Abort();
}
}
// Join Threads
Console.WriteLine("[Main] Waiting for Threads to finish.");
for (int i = 0; i < threads.Length; ++i) {
threads[i].Join();
threads[i] = null;
}
}

public static void StatementThreadFunc(object p)
{
StatementThreadParameters parameters = (StatementThreadParameters)p;
int recordcount = 0;
try {
using(DbConnection connection = new NpgsqlConnection(parameters.ConnectionString)) {
connection.Open();
using(DbCommand command = connection.CreateCommand()) {
command.CommandText = parameters.Statement;
using(DbDataReader datareader = command.ExecuteReader()) {
do {
if (datareader.HasRows) {
while (datareader.Read()) {
recordcount++;
}
}
} while (datareader.NextResult());
}
}
}
Console.WriteLine("[{0}] Successfully read {1} records.", parameters.ThreadId, recordcount);
} catch (ThreadAbortException) {
Console.WriteLine("[{0}] Thread aborted after {1} rows.", parameters.ThreadId, recordcount);
} catch (Exception ex) {
Console.WriteLine("[{0}] Unhandled exception caught after {1} rows ({2}): {3}", parameters.ThreadId, recordcount, ex.GetType().ToString(), ex.Message);
}
}

public class StatementThreadParameters
{
public string ThreadId;

public string ConnectionString;

public string Statement;

public StatementThreadParameters(string threadId, string connectionString, string statement)
{
this.ThreadId = threadId;
this.ConnectionString = connectionString;
this.Statement = statement;
}
}
}


I hope this can give you some more pointers. Thanks Jon, for your efforts so far. Please keep posting about changes in the CVS regarding this issue.

Thanks Jon and good luck,
Andreas


BTW: Yes, I still know killing threads with Thread.Abort() is bad. But its there in the framework and people and me will use it :-).
Date: 2008-03-10 18:51
Sender: Andreas Schönebeck

Hello Jon!

Checked out the ALPHA_3 CVS. I just want to give you a heads up regarding my initial bug report and test case. And the reader.HasRows issue is gone as well. So... finally this is what I was looking for:

[Main] Starting Thread [0].
[Main] Aborting Thread [0].
[Main] Waiting for Thread [0] to finish.
[0] Thread aborted after 0 rows.

[Main] Starting Thread [1].
[Main] Aborting Thread [1].
[Main] Waiting for Thread [1] to finish.
[1] Thread aborted after 0 rows.

[Main] Starting Thread [2].
[Main] Aborting Thread [2].
[Main] Waiting for Thread [2] to finish.
[2] Thread aborted after 12834 rows.

[Main] Starting Thread [3].
[Main] Aborting Thread [3].
[3] Thread aborted after 17127 rows.
[Main] Waiting for Thread [3] to finish.

[Main] Starting Thread [4].
[Main] Aborting Thread [4].
[Main] Waiting for Thread [4] to finish.
[4] Thread aborted after 13190 rows.

[Main] Starting Thread [5].
[Main] Aborting Thread [5].
[Main] Waiting for Thread [5] to finish.
[5] Thread aborted after 10645 rows.

[Main] Starting Thread [6].
[Main] Aborting Thread [6].
[Main] Waiting for Thread [6] to finish.
[6] Thread aborted after 1896 rows.

[Main] Starting Thread [7].
[Main] Aborting Thread [7].
[Main] Waiting for Thread [7] to finish.
[7] Thread aborted after 15984 rows.

[Main] Starting Thread [8].
[Main] Aborting Thread [8].
[Main] Waiting for Thread [8] to finish.
[8] Thread aborted after 11083 rows.

[Main] Starting Thread [9].
[Main] Aborting Thread [9].
[Main] Waiting for Thread [9] to finish.
[9] Thread aborted after 23156 rows.

[Main] Starting Thread [10].
[Main] Waiting for Thread [10] to finish.
[10] Successfully read 60050 records.
Press any key to continue . . .


No exceptions, no broken connections and intermediate results. Brillant work, thanks for your efforts. Of course it's just a test case so far and tomorrow I will try it out in my real projects. Can't wait, but I'm a bit sick as well and need to go home and sleep :-)

I'll give some real testing feedback tomorrow. So long,
Andreas
Date: 2008-03-10 11:05
Sender: Jon Hanna

Firstly, my apologies for my delay in getting back. Between being busy, then sick, then busy again I wasn't able to look at this at all for some time, and then when I could I could work away, but had limited access to the internet :(

In the meantime, Francisco has very graciously given me commit access, so I've put this stuff into a new branch, since it's still a lot of changes that interlink with each other.

RELEASE_2_0_ALPHA3 is the branch in question. Check that branch out and ye can work away.

I changed the build and 2008 csproj files by hand but can't test them fully with my set-up, so they could definitely do with a change.

The code here definitely will need a re-compile of using code, and it will break some cases of running code as I am about to discuss in the Open-Discussion list.

Many thanks to anyone who tests this, and I hope I've managed to move us a tiny bit forward.
Date: 2008-02-15 10:55
Sender: Jon Hanna

Andreas, I've found the cause of the last two issues and will be fixing those soon, as well as redefining the patches to be relative to Francisco's last commit.

I'm still at a loss as to what is causing the parameter type bug :(

Hopefully now I can get the n-unit tests working and that should help immensely.
Date: 2008-02-13 19:24
Sender: Francisco Figueiredo jr.

sun on previous post should have been "run" :)

"You should run the [...]"
Date: 2008-02-13 19:20
Sender: Francisco Figueiredo jr.


Hi, Jon!

What problem are you having setting up NUnit tests?

You should sun the add_* scripts from testsuite/noninteractive folder.

I hope it helps.

Please, let me know if you have any other problems.
Date: 2008-02-12 18:41
Sender: Andreas Schönebeck

Hi Jon,

Got some more for you :-). I have problems with all of my queries using DataReader.HasRows before DataReader.Read().

/* Code */
using (datareader ...) {
if (datareader.HasRows) {
while (datareader.Read()) {
/* Never gets here. Exception on first Read(). */
}
}
}

/* Example output from Test Case */
[Main] Starting Thread [2].
[2] Unhandled exception caught after 0 rows (System.IO.InvalidDataException): Backend sent unrecognized response type: 0x00 ( )
[Main] Aborting Thread [2].
[Main] Waiting for Thread [2] to finish.


And another but "quite rare" NullReferenceException in NpgsqlConnector:

/* Example output from Test Case */
[Main] Starting Thread [6].
System.NullReferenceException: Der Objektverweis wurde nicht auf eine Objektinstanz festgelegt.
bei Npgsql.NpgsqlConnector.Close() in d:\Quellen\Kram\pgtest\Npgsql\Npgsql\NpgsqlConnector.cs:Zeile 698.[6] Unhandled exception caught after 504 rows (Npgsql.NpgsqlException): canceling statement due to user request
Severity: ERROR
Code: 57014
[Main] Aborting Thread [6].
[Main] Waiting for Thread [6] to finish.


Because of the first HasRows Problem, I still cannot use your patch in my latest-greatest-complex-mutithreaded production code to test it thoroughly. But I think we're getting there :-).

Thanks a lot,
Andreas




/* Here's some code */

using System;
using System.Threading;
using System.Data;
using System.Data.Common;
using Npgsql;

class Program
{
public static void Main(string[] args)
{
Random rnd = new Random();
for (int i = 0; i < 10; i++) {
RunTestAbort(i, rnd.Next(10, 200));
}
RunTestAbort(10, 0);

Console.Write("Press any key to continue . . . ");
Console.ReadKey(true);
}

public static void RunTestAbort(int id, int sleep)
{
Console.WriteLine();
Thread dbthread = new Thread(AbortThreadFunc);
Console.WriteLine("[Main] Starting Thread [{0}].", id);
dbthread.Start(id);

if (sleep != 0) {
Thread.Sleep(sleep);
Console.WriteLine("[Main] Aborting Thread [{0}].", id);
dbthread.Abort();
}

Console.WriteLine("[Main] Waiting for Thread [{0}] to finish.", id);
dbthread.Join();
}

public static void AbortThreadFunc(object threadparam)
{
int recordcount = 0;
int id = (int)threadparam;
NpgsqlConnectionStringBuilder csb = new NpgsqlConnectionStringBuilder();
csb.Host = "localhost";
csb.Database = "gps";
csb.UserName = "postgres";
csb.Password = "postgres";
try {
using(DbConnection connection = new NpgsqlConnection(csb.ConnectionString)) {
connection.Open();
using(DbCommand command = connection.CreateCommand()) {
command.CommandText = "SELECT * FROM original";
using(DbDataReader datareader = command.ExecuteReader()) {
do {
if (datareader.HasRows) {
while (datareader.Read()) {
recordcount++;
}
}
} while (datareader.NextResult());
Console.WriteLine("[{0}] Successfully read {1} records.", id, recordcount);
}
}
}
} catch (ThreadAbortException ex) {
Console.WriteLine("[{0}] Thread aborted after {1} rows.", id, recordcount);
} catch (Exception ex) {
Console.WriteLine("[{0}] Unhandled exception caught after {1} rows ({2}): {3}", id, recordcount, ex.GetType().ToString(), ex.Message);
}
}
}
Date: 2008-02-12 16:57
Sender: Andreas Schönebeck

And I'm using MS .Net 2.0 on Windows as well...
Date: 2008-02-12 16:55
Sender: Andreas Schönebeck

Hi Jon!

The new NpgsqlTypesHelper.cs indeed fixed the DbParameter problems. Of course I didn't look at the code of the new typeshelper. I just trust you :-).

Now here is the test case, which does not work with the files from ExpeimentFiles.zip but work with ExpeimentFiles.zip + NpgsqlTypesHelper.cs:

using System;
using System.Data;
using System.Data.Common;
using Npgsql;

class Program
{
public static void Main(string[] args)
{
TestWithParam(3997);

Console.Write("Press any key to continue . . . ");
Console.ReadKey(true);
}

public static void TestWithParam(int id)
{
int recordcount = 0;
NpgsqlConnectionStringBuilder csb = new NpgsqlConnectionStringBuilder();
csb.Host = "localhost";
csb.Database = "gps";
csb.UserName = "postgres";
csb.Password = "postgres";
try {
using(NpgsqlConnection con = new NpgsqlConnection(csb.ConnectionString)) {
con.Open();
using(NpgsqlCommand cmd = con.CreateCommand()) {
cmd.CommandText = "SELECT * FROM original WHERE id=@id";
NpgsqlParameter param = cmd.CreateParameter();
param.DbType = DbType.Int32;
param.Value = id;
param.ParameterName = "@id";
cmd.Parameters.Add(param);
using(NpgsqlDataReader sdr = cmd.ExecuteReader()) {
while (sdr.Read()) {
recordcount++;
}
Console.WriteLine("[{0}] Successfully read {1} records.", id, recordcount);
}
}
}
} catch (Exception ex) {
Console.WriteLine("[{0}] Unhandled exception caught after {1} rows ({2}): {3}", id, recordcount, ex.GetType().ToString(), ex);
}
}
}


I will go and do some tests with my fancy product now. Reporting back soon,
Andreas
Date: 2008-02-11 23:19
Sender: Jon Hanna

Thanks Andreas, but unfortunately I can't reproduce that one.

I remember Mono having an issue with static constructors, is this still the case? (I'm working on MS .NET here) - there's a static constructor hit during the code you say is complaining.

The attached copy of NpgsqlTypesHelper.cs might solve it if that's the case.

If not, could you provide a more complete test case that reproduces this?
Date: 2008-02-11 22:46
Sender: Jon Hanna

Nice one Andreas I'll check that out soon.

You're correct, now ThreadAbort is more likely to happen in Read() (though it could happen in ExecuteReader() too), handling of server-errors is quite different to deal with this.

I threw a lot of different things into this bunch of code because I was expecting to test it for a lot longer before I built a patch, but then I figured it might be smarter to get eyeballs on it sooner rather than later.

Too tired from proper work now, but I did try running it against long queries to see how it goes. In the graph the X axis is how many rows the query returns, time until first result is green with the current code and blue with this code, time until last result is red with the current code and black with this code. Memory usage (a very rough measure - garbage collect and measure with GC before starting then measure with GC without collecting afterwards) is gray with the new code and purple with the current code). The limit it hits off is where it's taking up pretty much all available memory.
Date: 2008-02-11 11:16
Sender: Andreas Schönebeck

Thanks, Jon.

My little test app from the forum thread now works as it should. But maybe a point worth mentioning: the ThreadAbortExceptions are not happening in ExecuteReader() anymore but in Read(). Is there a subtle difference in Error/Exception handling between the two?

Anyway, no connections are orphaned in PostgreSQL after running the example and no weird stream exceptions happen anymore. Good.

But now trying to use DbParameters throws an exception:
/* Code Example */
param = command.CreateParameter();
param.DbType = DbType.Int16;
/* Thrown exception */
Unhandled Exception (System.InvalidCastException: Der Typ Int16 kann nicht in einen gültigen DbType umgewandelt werden.
bei Npgsql.NpgsqlParameter.set_DbType(DbType value) in d:\Npgsql\Npgsql\NpgsqlParameter.cs:Zeile 324.

The same applies for DbType.Int32. Bad. Until I can use DbParameters with your patch I cannot do further tests with my production/complex/multithreaded line of code. Which I really would like to do. That's where Npgsql really gets stressed.

Good start though, the original test code works so far,
Andreas
Date: 2008-02-11 08:43
Sender: Jon Hanna

Yep, it'll be handier for me too to be referencing the updated CVS.

Do those N-Unit tests require a particular database set-up? I've been trying to use them, but even with a clean CVS checkout I can't get most of them to work :(
Date: 2008-02-11 05:16
Sender: Francisco Figueiredo jr.


Hi, Jon!

I started doing some tests with your code and when running nunit tests they hang and server complains about encoding :( But I think this problem occurs on some specific tests. I will isolate them and will let you know of any news I found about them.

Thanks in advance and keep the good work!!
Date: 2008-02-11 04:38
Sender: Francisco Figueiredo jr.


Hi, Jon!

Great job!

Now that I commited array handling support in cvs, would you mind generating patches again against current cvs code? Thanks in advance.
Date: 2008-02-10 17:20
Sender: Jon Hanna

Oh, a few other things contained in this:

1. Only use UTF-8 for client encoding.
2. Objects that are created by reading from the stream do so as part of their constructors, so that they can never exist in a half-created state.
3. Similar change to constructor for type-mapping.
4. Bug-fix on limstring for multi-byte characters.
5. Asynchronous calls to Execute* methods on command object.

Changes:

Field Old Value Date By
File Added311: NpgsqlTypesHelper.cs2008-02-11 23:19talliesin
File Added310: graph.png2008-02-11 22:46talliesin
File Added309: ExpeimentFiles.zip2008-02-10 17:18talliesin
File Added308: experiment.zip2008-02-10 17:16talliesin
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