Ray tracing: error in scene.compute_paths(), if scattering is activated and more than one receiver in the scene

[member67]

Summary

In the ray-tracing tutorial, when executing scene.compute_paths(), I get an error if multiple (more than one) receivers are present in the scene and if the parameter "scattering" is set to True.
For example:

rx2 = Receiver(name="rx2",
               position=[45, 90, 0.5],
               orientation=[0, 0, 0])
scene.add(rx2)
paths = scene.compute_paths(max_depth=1, diffraction=False, scattering=True)

results in the following error:

tensorflow.python.framework.errors_impl.InvalidArgumentError: {{function_node __wrapped__GatherV2_device_/job:localhost/replica:0/task:0/device:CPU:0}} indices[88,0,2650] = -1 is not in [0, 218) [Op:GatherV2] name: 

Process finished with exit code 1

I run compute_paths() on a CPU, no GPU is involved.

System configuration

System information: [running on CPU, I explicitly switch off the GPU]

OS: Ubuntu 20.04.6 LTS
CPU: Intel(R) Xeon(R) CPU E5-2697 v4 @ 2.30GHz
GPU: Quadro M5000
Python: 3.9.17 (main, Jul 5 2023, 20:41:20) [GCC 11.2.0]
NVidia driver: 545.29.02
CUDA: 12.2.128
LLVM: -1.-1.-1

Dr.Jit: 0.4.3
Mitsuba: 3.4.0
Is custom build? False
Compiled with: GNU 10.2.1
Variants:
scalar_rgb
scalar_spectral
cuda_ad_rgb
llvm_ad_rgb

OS version: Linux-5.15.0-78-generic-x86_64-with-glibc2.31
processor: X86_64 [GenuineIntel]
tensorflow version: 2.15.0
sionna version: 0.15.1

Description

I run the ray-tracing tutorial. I add one more receiver to the scene, and explicitly set the scattering parameter to False as follows.

rx2 = Receiver(name="rx2",
               position=[45, 90, 0.5],
               orientation=[0, 0, 0])
scene.add(rx2)
paths = scene.compute_paths(max_depth=1, diffraction=False, scattering=True)

Every time that there is more than one receiver in the scene and scattering is activated, I end up with the following error in the scene.compute_paths() method:

Traceback (most recent call last):
  File "[...]/main.py", line 1193, in trace_cirs
    all_paths = scene.compute_paths(max_depth=p_radio_options['max_depth'],
  File "/media/hdd/miniconda/envs/pychEnv3/lib/python3.9/site-packages/sionna/rt/scene.py", line 564, in compute_paths
    paths = self._solver_paths(max_depth,
  File "/media/hdd/miniconda/envs/pychEnv3/lib/python3.9/site-packages/sionna/rt/solver_paths.py", line 627, in __call__
    all_paths = self._compute_paths_coefficients(rx_rot_mat,
  File "/media/hdd/miniconda/envs/pychEnv3/lib/python3.9/site-packages/sionna/rt/solver_paths.py", line 4136, in _compute_paths_coefficients
    k_x = tf.gather(xpd_coefficient, paths_tmp.scat_last_objects)
  File "/media/hdd/miniconda/envs/pychEnv3/lib/python3.9/site-packages/tensorflow/python/util/traceback_utils.py", line 153, in error_handler
    raise e.with_traceback(filtered_tb) from None
  File "/media/hdd/miniconda/envs/pychEnv3/lib/python3.9/site-packages/tensorflow/python/framework/ops.py", line 5883, in raise_from_not_ok_status
    raise core._status_to_exception(e) from None  # pylint: disable=protected-access
tensorflow.python.framework.errors_impl.InvalidArgumentError: {{function_node __wrapped__GatherV2_device_/job:localhost/replica:0/task:0/device:CPU:0}} indices[88,0,2650] = -1 is not in [0, 218) [Op:GatherV2] name: 

Process finished with exit code 1

The indices in "indices" are different (seems random) each time, so the last line in the error message may say:

[...] indices[40,0,2670] = -1 is not in [0, 218) [Op:GatherV2] name: 
[...] indices[29,0,2631] = -1 is not in [0, 218) [Op:GatherV2] name: 
[...] indices[36,0,2652] = -1 is not in [0, 218) [Op:GatherV2] name: 
[...] indices[48,0,860] = -1 is not in [0, 218) [Op:GatherV2] name: 

I can't tell whether these indices have any meaning - I do not see any connection to my scene.

If I set the scattering parameter to False, i.e.,
paths = scene.compute_paths(max_depth=8, diffraction=True, scattering=False)
the paths are computed without a problem.
However, scattering and having multiple recievers are both key requirements for me.

I have seen issues with a similar error message, and they said "solved" with the latest Sionna version (0.15.1). However, I have that version and the error still occurs.

By the way, if I run through the single receiver locations in a for loop (calling compute_paths each time with a single receiver) instead of having a number of receivers at the same time, I run into the following error:

Assertion failed in /project/ext/drjit-core/ext/nanothread/src/queue.cpp:354: remain == 1
Process finished with exit code 134 (interrupted by signal 6: SIGABRT)

as described here: mitsuba-renderer/mitsuba3#849 (comment)

Steps to reproduce

1. adapt ray tracing tutorial such that there are two receivers, e.g., scene.add(rx2)
2. compute paths with scene.compute_paths(scattering=True)

[faycalaa]

Hi,

Thank you for reporting this issue. We were able to reproduce it and it will be fixed in the next release.

[faycalaa]

Fixed by v0.16.