# WASM Threading memory out of bounds
**URL:** https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917
**Category:** Support
**Created:** [November 25, 2024, 3:57pm UTC](https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917 "2024-11-25T15:57:37Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Jens\_Munk\_Hansen](https://discourse.vtk.org/u/Jens_Munk_Hansen)
#### Post date: [November 25, 2024, 3:57pm UTC](https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917/1 "2024-11-25T15:57:37Z")
Hi Developers
I can get WebGPU to work fine with the release candidate 9.4.0. I am little puzzled, why you require “-sASYNCIFY” to be used. I would prefer the calls to be blocking, e.g. `GetRenderWindow()`.
I am working on establishing a better debug, but currently I ran into some memory if build with threading (32-bit).
My build setup (external project using VTK).
```auto
list(APPEND emscripten_link_options
"-lembind"
"-sWEBGL2_BACKWARDS_COMPATIBILITY_EMULATION"
"-sMODULARIZE=1"
"-sASYNCIFY=1"
"-sASYNCIFY_STACK_SIZE=81920"
"-sEXPORT_ES6=1"
"-sALLOW_MEMORY_GROWTH=1"
"-sEXPORT_NAME=VtkwebAssemblyModule"
"-sEXPORTED_RUNTIME_METHODS=['ENV', 'FS', 'ccall', 'stringToNewUTF8', 'addFunction']"
"-sEXPORTED_FUNCTIONS=['_free', '_malloc']"
# "-sDEFAULT_LIBRARY_FUNCS_TO_INCLUDE=['$addFunction']" # CMake adds another $ sign!
"-sINCLUDE_FULL_LIBRARY" # for addFunction
"-sALLOW_TABLE_GROWTH=1"
"-sERROR_ON_UNDEFINED_SYMBOLS=0"
)
if (ENABLE_THREADING)
list(APPEND emscripten_link_options
"SHELL:-s USE_PTHREADS=1"
"-pthread"
"SHELL:-s PTHREAD_POOL_SIZE=4"
"SHELL:-s OFFSCREENCANVAS_SUPPORT=1" # Proxy rendering to main browser thread
"SHELL:-s ENVIRONMENT=web,worker"
)
else()
list(APPEND emscripten_link_options
"SHELL:-s ENVIRONMENT=web"
)
endif()
```
I am using your most recent docker images. Your 32-bit works fine, the 32-bit with threading gives me the memory out of bounds at startup. I can see that WebGPU is found and the adapter information.
Any hints are welcome. If not, I will work on establishing a better debugging setup.
Thanks
Jens
---
### Author:  [@Jens\_Munk\_Hansen](https://discourse.vtk.org/u/Jens_Munk_Hansen)
#### Post date: [November 25, 2024, 3:59pm UTC](https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917/2 "2024-11-25T15:59:03Z")
Without threading, things works great. I also a little puzzled why I don’t get into the `vtkWebGPUPolyDataMapper`.
---
### Author:  [@jaswantp](https://discourse.vtk.org/u/jaswantp)
#### Post date: [November 25, 2024, 4:04pm UTC](https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917/3 "2024-11-25T16:04:20Z")
> [@Jens\_Munk\_Hansen](#):
>
> I can get WebGPU to work fine with the release candidate 9.4.0. I am little puzzled, why you require “-sASYNCIFY” to be used. I would prefer the calls to be blocking, e.g. `GetRenderWindow()`.
Simple answer is that webgpu (unlike webgl2) is async only. This has a contagious effect, requiring everything else (even embind funcs to become async)
> [@Jens\_Munk\_Hansen](#):
>
> I am using your most recent docker images. Your 32-bit works fine, the 32-bit with threading gives me the memory out of bounds at startup. I can see that WebGPU is found and the adapter information.
This looks like a static initialization issue. Cpp call stack with line numbers would definitely be helpful.
---
### Author:  [@Jens\_Munk\_Hansen](https://discourse.vtk.org/u/Jens_Munk_Hansen)
#### Post date: [November 25, 2024, 6:35pm UTC](https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917/4 "2024-11-25T18:35:22Z")
I realized that and changed a bunch of JavaScript code to handle the async nature. I will try tomorrow to get it to run in debug, so I get the callstack. I agree, it seems like an initialization issue. In debug mode, I got a some trace…
Tomorrow, I will try to establish a setup for debugging. I managed to do this before, but only for debugging my own code and the code from Emscripten.
---
### Author:  [@Jens\_Munk\_Hansen](https://discourse.vtk.org/u/Jens_Munk_Hansen)
#### Post date: [December 7, 2024, 11:57am UTC](https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917/5 "2024-12-07T11:57:17Z")
I figured it out. It was a simple out-of-memory. If I set the initial memory size, `-sINITIAL_MEMORY=1GB`, it went away. It was in the creation of a `vtkBuffer`, perhaps I should double check if we allocate memory here without handling out-of-memory properly.
---
### Author:  [@jaswantp](https://discourse.vtk.org/u/jaswantp)
#### Post date: [December 7, 2024, 3:22pm UTC](https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917/6 "2024-12-07T15:22:57Z")
Ah. Glad you figured it out. I vaguely recall seeing similar callstack not long ago that said table index was out of bounds. I’ll have to update the vtk emscripten docs page with this info.
---
### Author:  [@Jens\_Munk\_Hansen](https://discourse.vtk.org/u/Jens_Munk_Hansen)
#### Post date: [December 7, 2024, 5:33pm UTC](https://discourse.vtk.org/t/wasm-threading-memory-out-of-bounds/14917/7 "2024-12-07T17:33:06Z")
I did an interesting find. Random access to points and computing distances to a fixed point. I did this to investigate `-msimd128` and it turns out that no vectorization is made unless points are on a 16-byte boundary. Therefore invented a vtkScaledAOSDataArray (with padding). More interesting even without SIMD, the aligned memory is twice as fast as non-aligned memory. It has a significant impact reading less memory.