System() from a multi-threaded app
The man page for system(3S) states that its MT-Level is "unsafe." Nonetheless we need to call system() from a multi-threaded application. At present we "just go ahead and do it," and of course it doesn't work well. I'm not entirely sure of the details of the failure -- it's more a colleague's baby than mine -- but I believe the system() call often fails to complete ("hangs").
Is there a thread-safe equivalent-or-replacement for system()? Surely the need to launch other applications from a multi-threaded application is commonplace today? How is it done safely-and-correctly?
Hi,
system() is not thread safe because it internally uses vfork() system call which in turn is not MT-safe . When you do a vfork()/fork1() in threaded applications only the thread which issues the call gets duplicated in the child process , which could result in dead lock problems . Solution of running system() under the protection of a lock may not help to avoid this problem.
If you're using Solaris thread library , fork() + exec() is a safe substitute for system() . If you are using Posix library , use pthread_atfork() to make sure that you handle the locks properly before/after forking.
Hope this helps.
Thanks,
Prajeesh
Similar Messages
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Proble with multi-threaded app using the same connection
have a multi-threaded app. The threads all share the
same connection. They all do some selects / updates.
The OS is NT 4.0 and the application server is weblogic
Some times I am getting the error "java.sql.SQLException: Io exception: not in streaming mode"
and some times I am getting "java.sql.SQLException: Io exception: Protocal violation
Any Ideas?
Regards
SureshDon't create threads.... Your threads should if they are necessary be reusable, your threads should call the connections it needs from the cache service with let's say a max number of N pools (each pool a max number of M connections), if the connection domain asked exists on cache a connection is asked for corresponding pool, if the connection domain is not on cache the less used domain is thrown away (all inner connections closed first) and substituted by the new one requested. While the pool is not full keep creating connections as the request came (and all existing connections are being held and not released), when M connections exists, a request should wait till a connection is released.
If you can have 20 threads asking for the same connection and the max number of connections on pool is M=10, then yopur threads will wait for a connection being released. All this must be synchronized. You should set M the closest as possible to the normal number of requests you can imagine to happen the same time. You should get connection use it and release it right away if you can have a lot of requests.
I hope this helps you. -
"SQL-02103: Inconsistent cursor cache." error on a dual processor multi threaded apps
I have a C++ with Pro*C++ COM object running on a Win2000 OS on
a dual processor Middleware. The program is being called by a
service in a multi threaded way. An oracle error like ORA-2103
and SQL-02103 will be generated after running the program. We've
tried putting mutex on every SQL statement in Pro*C and it works
but the systems became very very slow. We concluded that the
error might be cause by a collision of threads accessing the
same Table or different tables having foreign constraints. This
is so because the error keeps coming from a statement accessing
Table A and following errors comes from a Table B having a
foreign key on Table A.
Our only solution now is to put Mutex on Statements accessing
same tables or tables with foreign constraints but this will
make our system run very very slow. I dont know if the problem
is in our Oracle Database because we already upgraded our system
from 8.1.6 to 8.1.7. The wierd thing on this is that the system
is running smoothly without oracle errors on a SINGLE PROCESSOR
Middleware. Hope you can give me any insights on this problem.I have a C++ with Pro*C++ COM object running on a Win2000 OS on
a dual processor Middleware. The program is being called by a
service in a multi threaded way. An oracle error like ORA-2103
and SQL-02103 will be generated after running the program. We've
tried putting mutex on every SQL statement in Pro*C and it works
but the systems became very very slow. We concluded that the
error might be cause by a collision of threads accessing the
same Table or different tables having foreign constraints. This
is so because the error keeps coming from a statement accessing
Table A and following errors comes from a Table B having a
foreign key on Table A.
Our only solution now is to put Mutex on Statements accessing
same tables or tables with foreign constraints but this will
make our system run very very slow. I dont know if the problem
is in our Oracle Database because we already upgraded our system
from 8.1.6 to 8.1.7. The wierd thing on this is that the system
is running smoothly without oracle errors on a SINGLE PROCESSOR
Middleware. Hope you can give me any insights on this problem. -
"SQL-02103: Inconsistent cursor cache." error on dual processor multi thread apps
I have a C++ with Pro*C++ COM object running on a Win2000 OS on
a dual processor Middleware. The program is being called by a
service in a multi threaded way. An oracle error like ORA-2103
and SQL-02103 will be generated after running the program. We've
tried putting mutex on every SQL statement in Pro*C and it works
but the systems became very very slow. We concluded that the
error might be cause by a collision of threads accessing the
same Table or different tables having foreign constraints. This
is so because the error keeps coming from a statement accessing
Table A and following errors comes from a Table B having a
foreign key on Table A.
Our only solution now is to put Mutex on Statements accessing
same tables or tables with foreign constraints but this will
make our system run very very slow. I dont know if the problem
is in our Oracle Database because we already upgraded our system
from 8.1.6 to 8.1.7. The wierd thing on this is that the system
is running smoothly without oracle errors on a SINGLE PROCESSOR
Middleware. Hope you can give me any insights on this problem.I have a C++ with Pro*C++ COM object running on a Win2000 OS on
a dual processor Middleware. The program is being called by a
service in a multi threaded way. An oracle error like ORA-2103
and SQL-02103 will be generated after running the program. We've
tried putting mutex on every SQL statement in Pro*C and it works
but the systems became very very slow. We concluded that the
error might be cause by a collision of threads accessing the
same Table or different tables having foreign constraints. This
is so because the error keeps coming from a statement accessing
Table A and following errors comes from a Table B having a
foreign key on Table A.
Our only solution now is to put Mutex on Statements accessing
same tables or tables with foreign constraints but this will
make our system run very very slow. I dont know if the problem
is in our Oracle Database because we already upgraded our system
from 8.1.6 to 8.1.7. The wierd thing on this is that the system
is running smoothly without oracle errors on a SINGLE PROCESSOR
Middleware. Hope you can give me any insights on this problem. -
VI calling from a multi-thread Teststand
Hello,
My test system tests four UUTs at the same time(with batch mode in TS), the code is based on LabVIEW and call from TS, so every step the same VI will be accessed by four thread. however, it runs quite slow even i set the reentrant execution in VI propertise.
My Quesition:
Can I do it like this in multi-thread mode of TS?
How can I make it fast? (convert VI to dll?????)
Any help will be appreciated.
Thanks,StevenHello Allen,
Thanks for your help.
Problem: I have a LabVIEW VI with parallel code blocks. These blocks run in parallel as expected when I run my VI directly or from a top level VI. However, the code blocks seem to run sequentially when I call my VI from TestStand. Why is this happening and how can I fix it?
Solution: In order to fix this behavior, simply set the VI Properties of "Execution" of your LabVIEW VI to "Other 1" or "Other 2". This change will make the parallel code blocks in your LabVIEW VI run in parallel as expected. To change this setting, from your LabVIEW VI, go to File»VI Properties. Select the Execution category. Change the Preferred Execution System to be either other 1 or other 2.
You need to make this change to any LabVIEW VI with parallel code blocks that is called from TestStand. The reason for this is that TestStand is using the LabVIEW ActiveX interface to run LabVIEW VIs. The LabVIEW ActiveX interface sets the caller's execution system to "User Interface" by default. This execution system is not recommended for a VI with parallel code blocks. If your LabVIEW VI's execution system is set to "Same as caller" (which is the default setting when creating a new LabVIEW VI), then it is executed in the User Interface thread when run through the LabVIEW ActiveX interface. This prevents the blocks to be executed in parallel.
In fact, only one block in my LabVIEW code, but it accessed by four thread from TS. I am sure that my VI can be accessed by four thread simultaneously if I enable the reentrant excution in VI property. I also have tried what mentioned in above document but no use.
However, if i only add a 1000ms delay to my LabView code instead of the 'calculation', it is fast enough! what is happening or something i set wrong?
I don't want to convert all my LabView code to DLL cos too many VIs here, and difficult for mantenance either.
Any other good solution???
Thank you Allen...
Steven -
Changing a Single Threaded app into Multi Threaded app
Hi Java Experts
I made a web crawler that goes out to a particular web site and starts from there to crawl throughout the internet -- it's working fine . it only has 1 thread -- which is the main class which implements runnable.
I'm interested in making this solution multithreaded in hopes that I can get greater performance. -- since I believe the limiting factor is probably the speed at which URLs are returned etc --
MY QUESTION: how would you guys turn such a crawler into a multithreaded application.
my main class -- that does all the real work (with the help of some other classes works like this )
getTheNextURL(String urlString)
//step 1: check if it's a valid url
//step 2: check if it's a url we are interested in
//step 3: go to the url and gather all the links on that page put them in an array list
//step 4: loop through the array list
//call getTheNextURL(urlname) inside of the step loop
Does anyone see any way to make this multithreaded ? for increased urls looked at I was hoping i could possible multiply the url search speed by a factor of the threads.
Thanks in Advance for any suggestions that can be offered.
stev
i'm also aware of the problem with my recursive calls as read in the oriely java perfomance tuning book i'm looking to resolve thatas well with the most optimum algorithmthanks for the suggestion sounds simple enough.
Since you made a great suggestion , what do you think about the recursion problem in my design.
Here's the problem
let's say the first web page it finds is a html page with the following links
link a
link b
link c
link d
It places these links in an ArrayList.
It loops through the ArrayList with an iterator and follows all the urls. starting with link a. On link a , the following link are found as seen below and placed in an ArrayList again.
link 1
link 2
link 3
link 4
then it will call the method again , which puts all the links found in an ArrayList and loops through it to follow the first.
This repeats over and over until it goes to the maximum depth specified , then it returns to the next iteration and looks through that. That's how it works in detail.
Every recursive call is an addition to the operating stack of the vm, so it's concievable that i may have 1000s of recursive calls stored on the stack each holding 1000s of ArrayList objects that it will consider.
I'm trying to figureout a better solution for this recursion to reduce the calls on the stack and implement multithreading at the same time.
Any ideas?
ps .
---- i would also like to be able to manually cancel threads that get caught in some infinite loop trick web pages out there. -
Hi all,
What is multi threading? How to implement multi threading in ABAP?
Regards,
BryanHi
How the vision connector framework works
The connector interacts with an SAP application using connector modules. The connector modules make calls to SAP's Native Interfaces and pass data (business object or event data) to and from an SAP application. The connector's flexible design enables different modules to be used for different tasks such as initializing the connector with the SAP application or passing business object data.
Communication between the connector and an SAP application
The connector uses SAP's Remote Function Call (RFC) library to communicate with an SAP application. SAP's RFC API allows external programs to call ABAP function modules within an SAP application.
Processing business objects
The connector is metadata driven. Metadata, in the WebSphere business integration system, is application-specific data that is stored in business objects and that assists a connector module in its interaction with the application. A metadata-driven connector module handles each business object that it supports based on metadata encoded in the business object definition rather than on instructions hard-coded in the connector module.
Business object metadata includes the structure of a business object, the settings of its attribute properties, and the content of its application-specific information. Because connector modules are metadata driven, they can handle new or modified business objects without requiring modifications to the connector-module code.
The vision connector framework uses the value of the verb application-specific information in the top-level business object to call the appropriate connector module to process the business object. The verb application-specific information provides the classname of the connector module.
The verb application-specific information of most top-level business objects must identify the classname of the connector module. The syntax of this verb application-specific information is:
AppSpecificInfo = PartialPackageName.ClassName,
For example,
AppSpecificInfo = sap.sapextensionmodule.VSapBOHandler,
In this example, sap.sapextensionmodule is the partial package name, and VSapBOHandler is the classname. The full package name includes the com.crossworlds.connectors prefix, which the WebSphere business integration system adds to the name automatically. In other words, the full text of the example is:
com.crossworlds.connectors.sap.sapextensionmodule.VSapBOHandler
Note:
The verb application-specific information of most top-level business objects must use a comma (,) delimiter after the connector classname. However, the Server verb, which is used by the RFC Server Module, is delimited instead by a semi-colon (;). For information about the Server verb, see How the RFC Server Module works and Supported verbs.
You need not specify the package name and classname for the verb application-specific information if the business object is used:
by the ALE Module to process application events; however, when you use the ALE Module to process service call requests, you must specify the package name and classname
by the ABAP Extension Module, which uses the default business object handler (sap.sapextensionmodule.VSapBOHandler)
Important:
Customer-generated connector modules that process business objects for the RFC Server Module must specify a full package name, which must begin with bapi. For example, bapi.client.Bapi_customer_getdetail2. The full package name in this example is bapi.client, and the classname is Bapi_customer_getdetail2.
Most business object processing is specific to each connector module. By default the connector uses the ABAP Extension Module. For more information on business object processing for the ABAP Extension Module, see Installing and customizing the ABAP Extension Module and Business object data routing to ABAP handlers. .
For more information on specifying verb application-specific information for the ALE Module, see Event processing and Processing multiple IDocs with a wrapper business object.
Processing multiple concurrent interactions
The Adapter Framework can create separate threads for processing an application event and a business object request. When processing multiple requests from the integration broker, it can create multiple threads to handle multiple business object requests. For example, when InterChange Server is the integration broker, the connector can receive multiple business object requests from multiple collaborations or from a multi-threaded collaboration.
Figure 4 illustrates the multi-threading architecture.
Figure 4. Multi-Threading Architecture of the Connector for SAP
Event processing
The connector performs the following steps when handling a poll call:
The Adapter Framework creates a single dedicated thread to handle poll calls. This thread calls the pollForEvents() method of the vision connector framework at the frequency specified in the PollFrequency configuration property.
The thread polls SAP, which uses a dialog process to locate and return the event.
Note:
If the connector's MaxNumberOfConnections configuration property evaluates to a number greater than 1, the vision connector framework dedicates a connection to SAP for polling. If MaxNumberOfConnections evaluates to 1, event and service-call request processing share a single connection to SAP.
The polling thread dies only when the connector shuts down.
Note:
Because the RFC Server connector agent pushes events out of SAP instead of polling for events, it spawns its own threads instead of using threads created by the connector framework. Because the ALE connector agent uses the RFC Server connector agent to access events, it also spawns its own threads instead of using threads created by the connector framework when it processes events.
Request processing
Independently of polling, the Adapter Framework can create multiple request-processing threads, one for each request business object. Each request thread instantiates the appropriate business object handler.
For example, when processing business object requests from InterChange Server, the number and type of business object handlers depends on the number and type of the collaborations sending the requests:
If multiple collaborations send business objects, each request thread instantiates a business object handler of the appropriate type.
If a multi-threaded collaboration sends multiple business objects of the same type, the request threads instantiate an equal number of business object handlers of that type.
If the connector's MaxNumberOfConnections configuration property evaluates to a number greater than 1, the vision connector framework dedicates one connection to SAP for polling and allocates the remaining connections to a pool used only for request processing.
As illustrated in Figure 4, the connector performs the following steps when handling a business object request:
The Adapter Framework creates a separate thread for each business object request. Each thread calls the doVerbFor() method of the Vision business object handler.
If the connector's MaxNumberOfConnections configuration property evaluates to a number greater than 1, the Vision business object handler checks the vision connector framework's connection pool to determine if a connection handle is available.
If the handle is available, the thread sends the request to SAP, which uses a dialog process to handle the request.
If the handle is not available, the thread waits until one becomes available. Thread sequencing determines the order in which each business object handler thread claims or waits for an available connection handle.
If the connector's MaxNumberOfConnections configuration property evaluates to 1, the Vision business object handler shares a connection with event processing.
SAP releases the dialog process after it completes processing and sends a return code.
The connector releases the connection handle after it receives the return code from SAP.
Setting the number of available connections
Use the MaxNumberOfConnections configuration property to specify the maximum number of connection handles available. The number of connections cannot exceed the number of dialog processes.
SAP locks the dialog process while processing an interaction, releasing it only when the interaction completes. Therefore, multiple concurrent requests lock an equal number of dialog processes until processing finishes.
Important:
Before setting a value for MaxNumberOfConnections, contact your SAP BASIS administrator to determine an appropriate value to maximize throughput without negatively affecting performance on the application server.
Support for multiple connections
By default the connector supports multiple-threads.
<b>
REWARD IF USEFULL</b> -
What's wrong with my multi-threaded Matrix Mult. code? 1 thread is fastest
For some reason, 1 thread performs the best. What's wrong with my implementation?
import java.util.Random;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class Matrix {
private int values[][];
private int rows;
private int columns;
public Matrix(int r, int c) {
this.rows = r;
this.columns = c;
this.values = new int[r][c];
private void randomize() {
Random generator = new Random();
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < this.columns; c++) {
this.values[r][c] = generator.nextInt(10);
public String toString() {
String out = "";
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < this.columns; c++) {
if (c == 0) out += "[";
else out += "\t";
out += this.values[r][c];
out += "]\n";
return out;
public boolean equals(Object obj) {
Matrix other = (Matrix) obj;
if (this.columns != other.columns || this.rows != other.rows) {
return false;
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < this.columns; c++) {
if (this.values[r][c] != other.values[r][c]) {
return false;
return true;
// matrix multiplication using single thread
public Matrix times(Matrix other) {
assert(this.columns == other.rows);
Matrix out = new Matrix(this.rows, other.columns);
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < other.columns; c++) {
int dotProduct = 0;
for (int z = 0; z < this.columns; z++) {
dotProduct += this.values[r][z] * other.values[z][c];
out.values[r][c] = dotProduct;
return out;
// matrix multiplication with many threads
public Matrix ptimes(Matrix other, int numberOfThreads) throws InterruptedException { // parallel
assert(this.columns == other.rows);
Matrix out = new Matrix(this.rows, other.columns);
ExecutorService threadExecutor = Executors.newFixedThreadPool(numberOfThreads);
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < other.columns; c++) {
threadExecutor.execute(new HelperThread(r, c, this, other, out));
threadExecutor.shutdown();
threadExecutor.awaitTermination(2, TimeUnit.DAYS);
return out;
private class HelperThread implements Runnable {
private int row;
private int col;
private Matrix a;
private Matrix b;
private Matrix out;
HelperThread(int r, int c, Matrix a, Matrix b, Matrix o) {
this.row = r;
this.col = c;
this.a = a;
this.b = b;
this.out = o;
public void run() {
int dotProduct = 0;
for (int z = 0; z < a.columns; z++) {
dotProduct += this.a.values[row][z] * this.b.values[z][col];
this.out.values[row][col] = dotProduct;
public static void main(String[] args) throws InterruptedException {
int size = 100;
Matrix a = new Matrix(size, size);
a.randomize();
Matrix b = new Matrix(size, size);
b.randomize();
for (int t = 1; t < 15; t++) {
long start = new Date().getTime();
System.out.print(t + " threads: ");
Matrix c = a.ptimes(b, t);
//System.out.println(c);
long finish = new Date().getTime();
System.out.println((finish - start) + " milliseconds");
Matrix d = a.times(b);
assert(c.equals(d));
}This one is even faster. On my dual core I get:
Warmup
Single Threaded
5.20616 milliseconds
5.52872 milliseconds
5.12708 milliseconds
5.59048 milliseconds
5.16104 milliseconds
5.1838 milliseconds
5.37104 milliseconds
5.1788 milliseconds
5.18636 milliseconds
5.15736 milliseconds
Multi Threaded with 2 threads
3.22184 milliseconds
2.86552 milliseconds
2.86284 milliseconds
3.67032 milliseconds
3.08032 milliseconds
2.97388 milliseconds
2.93084 milliseconds
3.44012 milliseconds
2.89744 milliseconds
2.88136 milliseconds
As you can see the Multi-Threaded versions are now faster.
// matrix multiplication with many threads
ExecutorService threadExecutor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
public Matrix ptimes(Matrix other) throws InterruptedException, ExecutionException {
assert (this.columns == other.rows);
Matrix out = new Matrix(this.rows, other.columns);
Future futures[] = new Future[rows];
for (int r = 0; r < this.rows; r++) {
futures[r] = threadExecutor.submit(new HelperThread(r, this, other, out));
for(Future f : futures) {
f.get();
return out;
private class HelperThread implements Callable<Object> {
private int row;
private Matrix a;
private Matrix b;
private Matrix out;
HelperThread(int r, Matrix a, Matrix b, Matrix o) {
this.row = r;
this.a = a;
this.b = b;
this.out = o;
public String call() throws Exception {
int dotProduct = 0;
for (int c = 0; c < b.columns; c++) {
for (int z = 0; z < a.columns; z++) {
dotProduct += this.a.values[row][z] * this.b.values[z][c];
this.out.values[row][c] = dotProduct;
return null;
public static void main(String[] args) throws InterruptedException, ExecutionException {
int size = 100;
Matrix a = new Matrix(size, size);
a.randomize();
Matrix b = new Matrix(size, size);
b.randomize();
System.out.println("Warmup");
for (int t = 0; t < 1000; t++) {
Matrix c = a.ptimes(b);
Matrix d = a.times(b);
assert (c.equals(d));
System.out.println("Single Threaded");
for (int t = 0; t < 10; t++) {
long start = System.nanoTime();
Matrix d = a.times(b);
long finish = System.nanoTime();
System.out.println((finish - start)/1000000.0 + " milliseconds");
System.out.println("Multi Threaded with " + Runtime.getRuntime().availableProcessors() + " threads");
for (int t = 0; t < 10; t++) {
long start = System.nanoTime();
Matrix c = a.ptimes(b);
long finish = System.nanoTime();
System.out.println((finish - start)/1000000.0 + " milliseconds");
Matrix d = a.times(b);
assert (c.equals(d));
System.exit(0);
} -
Hi folks,
I need to have one Connection object and multiple Statement objects created from this Connection Object. Is it safe to do this from a multi-threaded application?
Does createStatement() destroy any previously created Statement?You can have multiple statements in different threads coming of the same connection.
But, all such statements will be part of the same transacion. A DML in one thread will be reflected in a query in another thread.
If this not what you wanted, then you can have a connection pool and get connections from it in the individual threads. -
Cannot get bitmap from native DLL from multi threaded Java app.
I have a native DLL that gives me a HBITMAP (Windows handle to bitmap). I have made a JNI wrapper for this that gives me a BufferedImage back. The native code simple gets the actual bitmap for the handle, converts the RGB byte triplets to RGB ints, puts this in a jintArray and creates a BufferedImage.
This all works fine within a single Java thread. If I do this multi threaded (thread 1 calls the native function and several seconds later, thread 2 calls the native function) I keep getting the last image of the first thread. Can enyone help me out?
I know that this is probably a question for MSDN but I just know that they will tell me its a JNI question.
The native code:
JNIEXPORT jobject JNICALL Java_somenamespace_getPicture
(JNIEnv *env, jclass cl, jstring serialNumber)
jobject jImage;
jclass jImageClass;
jmethodID jMethod;
jfieldID jField;
jintArray rgbArray;
char *str;
char *charArray;
int *intArray;
int w, h, index, type;
HBITMAP hbmp;
BITMAP bmp;
str = (char*)((*env)->GetStringUTFChars(env, serialNumber, NULL));
// Gets the HBITMAP handle from the native DLL. The first argument is to select the device, based on serial number.
getPicture(str, &hbmp);
(*env)->ReleaseStringUTFChars(env, serialNumber, str);
// Get the BITMAP for the HBITMAP
GetObject(hbmp, sizeof(BITMAP), &bmp);
// Create my BufferedImage
jImageClass = (*env)->FindClass(env, "java/awt/image/BufferedImage");
jMethod = (*env)->GetMethodID(env, jImageClass, "<init>", "(III)V");
jField = (*env)->GetStaticFieldID(env, jImageClass, "TYPE_INT_RGB", "I");
type = (*env)->GetStaticIntField(env, jImageClass, jField);
jImage = (*env)->NewObject(env, jImageClass, jMethod, bmp.bmWidth, bmp.bmHeight, type);
// Get the RGB byte triplets of the BITMAP
charArray = (char *)malloc(sizeof(char) * bmp.bmHeight * bmp.bmWidth * 3);
GetBitmapBits(hbmp, sizeof(char) * bmp.bmHeight * bmp.bmWidth * 3, charArray);
// Allocate space to store the RGB ints and convert the RGB byte triplets to RGB ints
intArray = (int *)malloc(sizeof(int) * bmp.bmHeight * bmp.bmWidth);
index = 0;
for (h = 0; h < bmp.bmHeight; ++h)
for (w = 0; w < bmp.bmWidth; ++w)
int b = *(charArray + index * 3) & 0xFF;
int g = *(charArray + index * 3 + 1) & 0xFF;
int r = *(charArray + index * 3 + 2) & 0xFF;
*(intArray + index) = 0xFF000000 | (r << 16) | (g << 8) | b;
++index;
// Create a jintArray for the C RGB ints
rgbArray = (*env)->NewIntArray(env, bmp.bmHeight * bmp.bmWidth);
(*env)->SetIntArrayRegion(env, rgbArray, 0, bmp.bmHeight * bmp.bmWidth, (jint*)intArray);
// Use BufferedImage.setRGB() to fill the image
jMethod = (*env)->GetMethodID(env, jImageClass, "setRGB", "(IIII[III)V");
(*env)->CallVoidMethod(env, jImage, jMethod,
0, // int startX
0, // int startY
bmp.bmWidth, // int width
bmp.bmHeight, // int height
rgbArray, // int[] rgbArray
0, // int offset
bmp.bmWidth); // int scansize
// Free stuff
(*env)->DeleteLocalRef(env, rgbArray);
free(charArray);
free(intArray);
return jImage;
}I already tried working with native HDCs (GetDC, CreateCompatibleBitmap, SelectObject, GetDIBits, ...) but this just complicates stuff and gives me the same result.Have you verified what the "native DLL" gives you back on the second call?The HBITMAP handle returned is the same each call (no matter which thread). The actual BITMAP associated with this handle is only updated in the first thread.
How are you determining that the image is the same?If I point the camera (I don't get a stream, I just get individual images) to a moving scene, I get different images for each call from within the first thread. The second thread only gets the latest image from the first thread. There is no concurrency of the threads and all methods are synchronized.
Specifically did you verify that the problem is not that your test code itself is using the same instance?Yes, I tested the native side as well as the Java side. The BufferedImage is always an exact copy of the native BITMAP.
Try printing out the hash for each instance.I have written the image to a file in the native code itself to eliminate anything related to the mechanism of returning the BufferedImage. This had the same result.
The return values of all native calls all indicate successful calls.
I am suspecting the native side of creating a second graphical context for the second thread while it keeps refering to the first context.
(I will start a thread on the MSDN as well and will post here if anything turns up.) -
Aggregate Storage And Multi-Threading/Multi-Core Systems
Please pardon if this question has been asked before, but the Forum search is not returning any relevant results.
We are in the process of purchasing hardware for an 11.1.2 Essbase environment. We are going 64-bit, on Windows 2008, with either 32 GB or 64 GB of system RAM. The debate we are having is the number of CPUs and cores per CPU. We have not built any ASO databases as of yet, but we plan to launch a major BSO to ASO conversion project once 11.1.2 is off the ground here.
Historically, with BSO, we did not see performance improvements significant enough to justify the cost of additional CPUs when we ran calcs on multi-CPU systems vs. single or dual CPU systems, even when the settings and design should have taken the most advantage of BSO's multi-threading capabilities. However, it would seem that ASO's design may be able to make better use of multi-core systems.
I know that there are a lot of factors behind any system's performance, but in general, is ASO in 11.1.2 written well enough to make it worthwhile to consider, say, a four CPU, total 16 core system vs. a 2 CPU, total four core system?Grand central dispatch - infancy, not really doing its job, and I don't think apps have to be specifically written for HT, but they do have to not do things that they use to - prevent threads from going to sleep! or be parked.
high usage is not necessarily high efficiency. often the opposite.
Windows 7 seems to be optimized for multi-core thanks to a lot of reworking. Intel wants and knows it isn't possible to hand code, that the hardware has to be smarter, too. But the OS has a job, and right now I don't think it does it properly. Or handle memory.
Gulftown's 12MB cache will help, and over all should be 20% more efficient doing its work.
With dual processors, and it doesn't look like there are two quick path bridges, data shuffling has led to memory thrashing. Use to be page thrashing with not enough memory. Then core thrashing but having the cores, but not integrated (2008 is often touted as being greatest design so far, but it was FOUR dual-cores, 2009 was the first with a processor that really was new design and (native) 4-core.
One core should be owned by the OS so it is always available for its own work and housekeeping.
The iTunes audio bug last year showed how damaging and not to implement code and how a thread could usurp processing and add a high cpu temperature while basically doing nothing, sort of a denial of service attack on the processor - those 80*C temps people had.
All those new technology features under development and not like OpenCL, GCD and even OpenGL are tested, mature but rather 1.0 foundation for the future. A year ahead of readiness. -
How should implement multi-thread in single-threaded Operating system using
How should implement multi-thread in single-threaded Operating system using java?
Java supports "Multi-threading".Is there is any way run the multiple threads (Implementing multi threading) using java in a Single-threaded Operating system (That is the operating system does not support for multi-threading).Previous questions from OP suggest they are using J2ME, so the question might be possible.
806437 wrote:
How should implement multi-thread in single-threaded Operating system using java?
What is the actual question/problem?
A java app doesn't do threads or not do threads. It uses classes. The VM does threads.
So if you have a platform that does not have threads and you want to support the thread class then the VM, not a java app, must provide some pseudo mechanism, such as green threads, to support that.
If your question is about java code and not the VM then you must build a task engine and insure that the tasks are of short enough duration that it is an effective use for your system. -
SSRS - Is there a multi thread safe way of displaying information from a DataSet in a Report Header?
In order to dynamically display data in the Report Header based in the current record of the Dataset, we started using Shared Variables, we initially used ReportItems!SomeTextbox.Value, but we noticed that when SomeTextbox was not rendered in the body
(usually because a comment section grow to occupy most of the page if not more than one page), then the ReportItem printed a blank/null value.
So, a method was defined in the Code section of the report that would set the value to the shared variable:
public shared Params as String
public shared Function SetValues(Param as String ) as String
Params = Param
Return Params
End Function
Which would be called in the detail section of the tablix, then in the header a textbox would hold the following expression:
=Code.Params
This worked beautifully since, it now didn't mattered that the body section didn't had the SetValues call, the variable persited and the Header displayed the correct value. Our problem now is that when the report is being called in different threads with
different data, the variable being shared/static gets modified by all the reports being run at the same time.
So far I've tried several things:
- The variables need to be shared, otherwise the value set in the Body can't be seen by the header.
- Using Hashtables behaves exactly like the ReportItem option.
- Using a C# DLL with non static variables to take care of this, didn't work because apparently when the DLL is being called by the Body generates a different instance of the DLL than when it's called from the header.
So is there a way to deal with this issue in a multi thread safe way?
Thanks in advance!
Hi Angel,
Per my understanding that you want to dynamic display the group data in the report header, you have set page break based on the group, so when click to the next page, the report hearder will change according to the value in the group, when you are using
the shared variables you got the multiple thread safe problem, right?
I have tested on my local environment and can reproduce the issue, according to the multiple safe problem the better way is to use the harshtable behaves in the custom code, you have mentioned that you have tryied touse the harshtable but finally got
the same result as using the ReportItem!TextBox.Value, the problem can be cuased by the logic of the code that not works fine.
Please reference to the custom code below which works fine and can get all the expect value display on every page:
Shared ht As System.Collections.Hashtable = New System.Collections.Hashtable
Public Function SetGroupHeader( ByVal group As Object _
,ByRef groupName As String _
,ByRef userID As String) As String
Dim key As String = groupName & userID
If Not group Is Nothing Then
Dim g As String = CType(group, String)
If Not (ht.ContainsKey(key)) Then
' must be the first pass so set the current group to group
ht.Add(key, g)
Else
If Not (ht(key).Equals(g)) Then
ht(key) = g
End If
End If
End If
Return ht(key)
End Function
Using this exprssion in the textbox of the reportheader:
=Code.SetGroupHeader(ReportItems!Language.Value,"GroupName", User!UserID)
Links belowe about the hashtable and the mutiple threads safe problem for your reference:
http://stackoverflow.com/questions/2067537/ssrs-code-shared-variables-and-simultaneous-report-execution
http://sqlserverbiblog.wordpress.com/2011/10/10/using-custom-code-functions-in-reporting-services-reports/
If you still have any problem, please feel free to ask.
Regards
Vicky Liu -
"SQL-02103 Inconsistent cursor cache." error on dual processor multi threaded system
I have a C++ with Pro*C++ COM object running on a Win2000 OS on
a dual processor Middleware. The program is being called by a
service in a multi threaded way. An oracle error like ORA-2103
and SQL-02103 will be generated after running the program. We've
tried putting mutex on every SQL statement in Pro*C and it works
but the systems became very very slow. We concluded that the
error might be cause by a collision of threads accessing the
same Table or different tables having foreign constraints. This
is so because the error keeps coming from a statement accessing
Table A and following errors comes from a Table B having a
foreign key on Table A.
Our only solution now is to put Mutex on Statements accessing
same tables or tables with foreign constraints but this will
make our system run very very slow. I dont know if the problem
is in our Oracle Database because we already upgraded our system
from 8.1.6 to 8.1.7. The wierd thing on this is that the system
is running smoothly without oracle errors on a SINGLE PROCESSOR
Middleware. Hope you can give me any insights on this problem.I have a C++ with Pro*C++ COM object running on a Win2000 OS on
a dual processor Middleware. The program is being called by a
service in a multi threaded way. An oracle error like ORA-2103
and SQL-02103 will be generated after running the program. We've
tried putting mutex on every SQL statement in Pro*C and it works
but the systems became very very slow. We concluded that the
error might be cause by a collision of threads accessing the
same Table or different tables having foreign constraints. This
is so because the error keeps coming from a statement accessing
Table A and following errors comes from a Table B having a
foreign key on Table A.
Our only solution now is to put Mutex on Statements accessing
same tables or tables with foreign constraints but this will
make our system run very very slow. I dont know if the problem
is in our Oracle Database because we already upgraded our system
from 8.1.6 to 8.1.7. The wierd thing on this is that the system
is running smoothly without oracle errors on a SINGLE PROCESSOR
Middleware. Hope you can give me any insights on this problem. -
Hi,
I have a multi-threaded EWS app that is pushing email, appointments, and contacts to Exchange2010SP3. Each thread is using a separate instance ExchangeService and is working with a different mailbox on each thread. We are seeing that
when 4 or more threads are running we are starting to see ArgumentOutOfRange [Count cannot be less then zero] exceptions in the EWS library. These errors appear to be happening sporadically.
Here is an example of one of stack traces:
Stack Trace --
at System.String.CopyTo(Int32 sourceIndex, Char[] destination, Int32 destinationIndex, Int32 count)
at System.IO.StreamWriter.Write(String value)
at System.IO.TextWriter.SyncTextWriter.Write(String value)
at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.BuildEwsHttpWebRequest()
at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(IEwsHttpWebRequest& request)
at Microsoft.Exchange.WebServices.Data.ExchangeService.InternalBindToItems(IEnumerable`1 itemIds, PropertySet propertySet, ServiceErrorHandling errorHandling) at Microsoft.Exchange.WebServices.Data.ExchangeService.BindToItem[TItem](ItemId itemId, PropertySet
propertySet) at Quest.Apollo.MigrationProviders.Interfaces.GenericRetryAction.InternalRetry[T](RetryMethod`1 retryMethod) in c:\Builds\272\Apollo\1.6.0 Nightly\Sources\Apollo.MigrationProviders.Interfaces\GenericRetryAction.cs:line 111 at Quest.Apollo.MigrationProviders.Interfaces.GenericRetryAction.Retry[T](RetryMethod`1
retryMethod, Boolean disableRetry) in c:\Builds\272\Apollo\1.6.0 Nightly\Sources\Apollo.MigrationProviders.Interfaces\GenericRetryAction.cs:line 135
These exceptions are occurring on various EWS operations, but mostly on FindItems and Bind operations. They only seem to occur against Exchange 2010 servers at least that's what I've seen so far. These issues appear to resemble some kind of race condition.
I did some searches on EWS, Race Condition, SyncTextWriter and I came across an interesting issue while searching on SyncTextWriter and Race Condition. I'm curious if this is what is causing this error to occur in the EWS library:
http://connect.microsoft.com/VisualStudio/feedback/details/249253/synchronized-textwriter-not-synchronizing-properly
The post indicates that SyncTextWriter was only designed to synchronize multiple threads against the same instance and that it was not designed to synchronize multiple threads against multiple instances SyncTextWriter. I've noticed that in all instances
of this error I've seen the stack traces always end up inside of SyncTextWriter. Is this a bug in the EWS libraries use of SyncTextWriter? Note: the above article does post workarounds for this issue. Can't tell if the EWS library is using any of these workarounds
or is avoiding this issue in some other way.
I know Microsoft doesn't claim that the EWS library is thread safe. However, I've seen many posts that seem to indicate that if a separate instances of the exchange service are used for each thread it works fine. Futhermore, we've run this app many times against
Office 365 and haven't seen this issue. It appears to only happen against Exchange 2010, but that maybe due to better throughput to the Exchange 2010 server compared to the Office 365 servers. Any help or insight would be greatly appreciated.
Thanks,
Steve
Hi,
Found a note explaining the significance of these errors.
It says:
"NZE-28862: SSL connection failed
Cause: This error occurred because the peer closed the connection.
Action: Enable Oracle Net tracing on both sides and examine the trace output. Contact Oracle Customer support with the trace output."
For further details you may refer the Note: 244527.1 - Explanation of "SSL call to NZ function nzos_Handshake failed" error codes
Thanks & Regards,
Sindhiya V.
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