Real-Time Physics Simulation Forum

Re: CPU multithreading is working!

2018-11-22T11:12:20+00:00

Submitted an new issue I found with multithreading.

https://github.com/bulletphysics/bullet3/issues/2002

Statistics: Posted by badyolk — Thu Nov 22, 2018 11:12 am

Re: CPU multithreading is working!

2018-05-05T10:40:05+00:00

I am having trouble reproducing this crash. I have latest code from bullet main repo. Using Cmake and building with multithreading enabled. I applied the suggested change to MultiThreadedDemo::createStack function. Compiled on windows 10 with MSVC 2015, 64-bit, RelWithDebInfo configuration.

I compiled with configuration you mentioned and this work without problems.
I encountered problems for 32-bit, Debug, Windows10.

Here is log (with assert):

Code:

Version = 4.5.0 - Build 22.20.16.4836Vendor = IntelRenderer = Intel(R) HD Graphics 630starting thread 0started TaskScheduler thread 0 with threadHandle 00000378starting thread 1started TaskScheduler thread 1 with threadHandle 00000384starting thread 2started TaskScheduler thread 2 with threadHandle 00000390starting thread 3started TaskScheduler thread 3 with threadHandle 0000039Cstarting thread 4started TaskScheduler thread 4 with threadHandle 000003A8starting thread 5started TaskScheduler thread 5 with threadHandle 000003B4starting thread 6started TaskScheduler thread 6 with threadHandle 000003C0b3Printf: Selected demo: Multithreaded DemoAssert D:\Libraries\Bullet\bullet3-2018_05_03-modified\src\BulletDynamics\ConstraintSolver\btBatchedConstraints.cpp:215 (conInfo.numConstraintRows <= 6)

Edit

Thanks for the reply. Can you report the issue in the Bullet https://github.com/bulletphysics/bullet3/issues tracker, so we can track progress on fixes?

Issue added.
https://github.com/bulletphysics/bullet3/issues/1673

Statistics: Posted by przemir — Sat May 05, 2018 10:40 am

Re: CPU multithreading is working!

2018-05-04T22:59:38+00:00

To reproduce problem with a small amount of code, I modified your sample (MultiThreadedDemo) a bit, i.e replaced fragment of method MultiThreadedDemo::createStack

from:

Code:

btRigidBody* body = localCreateRigidBody( mass, trans, boxShape );body->setFriction( 1.0f );body->setRollingFriction( gSliderRollingFriction );

to:

Code:

if(iX % 2 == 0) {btRigidBody* body = localCreateRigidBody( mass, trans, boxShape );body->setFriction( 1.0f );body->setRollingFriction( gSliderRollingFriction );}else {btCollisionObject* collisionObject = new btCollisionObject();collisionObject->setWorldTransform(trans);collisionObject->setCollisionShape(boxShape);m_dynamicsWorld->addCollisionObject(collisionObject);}

Now it causes crash.

I am having trouble reproducing this crash. I have latest code from bullet main repo. Using Cmake and building with multithreading enabled. I applied the suggested change to MultiThreadedDemo::createStack function. Compiled on windows 10 with MSVC 2015, 64-bit, RelWithDebInfo configuration.
When I run the MultiThreadedDemo it isn't crashing and half of the boxes are not dynamic as expected.
Am I missing a step?

Statistics: Posted by lunkhound — Fri May 04, 2018 10:59 pm

Re: CPU multithreading is working!

2018-05-04T21:14:00+00:00

I'll investigate this crash shortly.

Statistics: Posted by lunkhound — Fri May 04, 2018 9:14 pm

Re: CPU multithreading is working!

2018-05-03T14:56:03+00:00

Thanks for the reply. Can you report the issue in the Bullet https://github.com/bulletphysics/bullet3/issues tracker, so we can track progress on fixes?

1. My program using single-threaded btDiscreteDynamicsWorld crashed because of btSequentialImpulseConstraintSolver::getOrInitSolverBody method returned -1
It happened because of line:
Code:
if ( btRigidBody* rb = btRigidBody::upcast( &body ) )
I use CollisionObjects aside from RigidBodies. After I commented line above, single-threaded simulation started to work again.
Similar line is in btSequentialImpulseConstraintSolverMt::getOrInitSolverBodyThreadsafe though.

2. After configuring btDiscreteDynamicsWorldMt with specified btSequentialImpulseConstraintSolverMt program crashes as well.
For btDiscreteDynamicsWorldMt without btSequentialImpulseConstraintSolverMt it works.
I guess (like in the case above) it may have problems when there are pure CollisionObjects inside dynamic world aside from RigidBodies.
To reproduce problem with a small amount of code, I modified your sample (MultiThreadedDemo) a bit, i.e replaced fragment of method MultiThreadedDemo::createStack

from:
Code:
btRigidBody* body = localCreateRigidBody( mass, trans, boxShape );body->setFriction( 1.0f );body->setRollingFriction( gSliderRollingFriction );
to:
Code:
if(iX % 2 == 0) {btRigidBody* body = localCreateRigidBody( mass, trans, boxShape );body->setFriction( 1.0f );body->setRollingFriction( gSliderRollingFriction );}else {btCollisionObject* collisionObject = new btCollisionObject();collisionObject->setWorldTransform(trans);collisionObject->setCollisionShape(boxShape);m_dynamicsWorld->addCollisionObject(collisionObject);}
Now it causes crash.

Statistics: Posted by Erwin Coumans — Thu May 03, 2018 2:56 pm

Re: CPU multithreading is working!

2018-05-03T14:32:27+00:00

Note that my pull-request for the multithreaded constraint solver has been accepted and merged (a couple of weeks ago). So this is now available in the main Bullet repo.

Thanks for sharing your code.

1. My program using single-threaded btDiscreteDynamicsWorld crashed because of btSequentialImpulseConstraintSolver::getOrInitSolverBody method returned -1
It happened because of line:

Code:

if ( btRigidBody* rb = btRigidBody::upcast( &body ) )

I use CollisionObjects aside from RigidBodies. After I commented line above, single-threaded simulation started to work again.
Similar line is in btSequentialImpulseConstraintSolverMt::getOrInitSolverBodyThreadsafe though.

2. After configuring btDiscreteDynamicsWorldMt with specified btSequentialImpulseConstraintSolverMt program crashes as well.
For btDiscreteDynamicsWorldMt without btSequentialImpulseConstraintSolverMt it works.
I guess (like in the case above) it may have problems when there are pure CollisionObjects inside dynamic world aside from RigidBodies.
To reproduce problem with a small amount of code, I modified your sample (MultiThreadedDemo) a bit, i.e replaced fragment of method MultiThreadedDemo::createStack

from:

Code:

btRigidBody* body = localCreateRigidBody( mass, trans, boxShape );body->setFriction( 1.0f );body->setRollingFriction( gSliderRollingFriction );

to:

Code:

if(iX % 2 == 0) {btRigidBody* body = localCreateRigidBody( mass, trans, boxShape );body->setFriction( 1.0f );body->setRollingFriction( gSliderRollingFriction );}else {btCollisionObject* collisionObject = new btCollisionObject();collisionObject->setWorldTransform(trans);collisionObject->setCollisionShape(boxShape);m_dynamicsWorld->addCollisionObject(collisionObject);}

Now it causes crash.

Statistics: Posted by przemir — Thu May 03, 2018 2:32 pm

Re: CPU multithreading is working!

2018-04-15T20:40:10+00:00

Note that my pull-request for the multithreaded constraint solver has been accepted and merged (a couple of weeks ago). So this is now available in the main Bullet repo.
Thanks Erwin!

With this latest PR, the task scheduler is now included in the core libs, which should make it easier than ever to get multithreading working in a standalone project. Feel free to post in this thread if you run into any trouble getting it set up.

Statistics: Posted by lunkhound — Sun Apr 15, 2018 8:40 pm

Re: CPU multithreading is working!

2018-03-08T19:58:14+00:00

Thanks. I was using the wrong master, which doesn't have the btSequentialImpulseConstraintSolverMt source files. I'll build it now and let you know what I think after a couple of days of testing.

Sorry, that was my bad -- I had the wrong default branch on my repo. I fixed that now.

If you should run into any trouble, just post it here and I'll try to help. Also, for best results I recommend using the built-in task scheduler rather than the others. I haven't been testing the others much.

Statistics: Posted by lunkhound — Thu Mar 08, 2018 7:58 pm

Re: CPU multithreading is working!

2018-03-08T19:16:44+00:00

Thanks. I was using the wrong master, which doesn't have the btSequentialImpulseConstraintSolverMt source files. I'll build it now and let you know what I think after a couple of days of testing.

Statistics: Posted by rebirth — Thu Mar 08, 2018 7:16 pm

Re: CPU multithreading is working!

2018-03-08T18:51:42+00:00

I've tried getting this working, but VS is throwing an assert:

Code:

btAssert( gBtTaskScheduler != NULL );  // call btSetTaskScheduler() with a valid task scheduler first! - line 444 of btThreads.cpp

I chose PPL in cmake and I'm creating the world like so:

Code:

broadPhase = new btDbvtBroadphase();collisionConfig = new btDefaultCollisionConfiguration();collisionDispatcher = new btCollisionDispatcherMt(collisionConfig, 40);solver = new btConstraintSolverPoolMt(BT_MAX_THREAD_COUNT);dynamicsWorld = new btDiscreteDynamicsWorldMt(collisionDispatcher, broadPhase, solver, collisionConfig);

Am I missing something?

It looks like you are not setting up a task scheduler. To use PPL you would add something like:

Code:

btSetTaskScheduler( btGetPPLTaskScheduler() );

Note that the version of bullet multithreading I just recently posted about, is still only a Pull Request -- it is not (yet) present in the main Bullet repo.
However you can get it here:
https://github.com/lunkhound/bullet3

Note the world setup is changed slightly to allow for the new parallel solver:

Code:

broadPhase = new btDbvtBroadphase();collisionConfig = new btDefaultCollisionConfiguration();collisionDispatcher = new btCollisionDispatcherMt(collisionConfig, 40);solverPool = new btConstraintSolverPoolMt(BT_MAX_THREAD_COUNT);parallelSolver = new btSequentialImpulseConstraintSolverMt();  // create parallel solverdynamicsWorld = new btDiscreteDynamicsWorldMt(collisionDispatcher, broadPhase, solverPool, parallelSolver, collisionConfig);btSetTaskScheduler( btCreateDefaultTaskScheduler() );  // use built-in task scheduler

Statistics: Posted by lunkhound — Thu Mar 08, 2018 6:51 pm