Sam Pfeiffer awesomebytes

Compile Kernel with PREEMPT_RT

When following https://docs.ros.org/en/foxy/Tutorials/Miscellaneous/Building-Realtime-rt_preempt-kernel-for-ROS-2.html

I built this in a VM using the Ubuntu ubuntu-20.04.5-desktop-amd64.iso. I needed to provide the VM with 7GB of RAM to avoid OOM (out of memory) errors. I needed to provide it with 60GB of storage space (Ubuntu installation needs short of 7GB and the kernel compilation seems to need over 40GB, plus testing the .deb installation it fills the disk).

39G	linux-5.15.73
8.2M	linux-headers-5.15.73-rt52_5.15.73-rt52-8_amd64.deb
84M	linux-image-5.15.73-rt52_5.15.73-rt52-8_amd64.deb
1.2G	linux-image-5.15.73-rt52-dbg_5.15.73-rt52-8_amd64.deb
1.2M	linux-libc-dev_5.15.73-rt52-8_amd64.deb

How to publish with rostopic pub in a launchfile with a complex message

Using the dictionary syntax: http://wiki.ros.org/ROS/YAMLCommandLine#Command-line_and_messages_.28dictionaries.29 We avoid the problem of requiring double quotes inside of the args field. (I found no way to realiably escape the quotes, for double quote I used " and for single quote I used ' but I still was getting errors).

<launch>
    <!-- Publishing a dummy empty pointcloud (but with x y z fields described to avoid
    errors like: Failed to find match for field 'x'. ) -->
    <node name="dummy_pointcloud_pub" pkg="rostopic" type="rostopic"

How to reset the GPU to use CUDA after suspend or hibernation

I needed to do:

sudo rmmod nvidia_uvm
sudo modprobe nvidia_uvm

From the nvidia forums.

I also got the following error fixed (docker-nvidia related) with these commands:

Datestamp

DATESTAMP=$(date +"%Y_%m_%d_%H_%M")

	#!/usr/bin/env python

	import sys
	import rospy
	from sensor_msgs.msg import Image, CompressedImage
	import numpy as np
	import cv2
	from cv_bridge import CvBridge, CvBridgeError

	"""

	#!/usr/bin/env python
	import itertools
	import sys
	import time
	import rospy
	import rosbag
	import message_filters

	"""
	Example using a message_filters filter (ApproximateTimeSynchronizer) iterating

	# How to play audio from inside a docker container
	```bash
	# Run your docker image with
	-v /run/user/$UID/pulse/native:/run/user/$UID/pulse/native \
	-e PULSE_SERVER=unix:/run/user/$UID/pulse/native
	```

	And you can try to use `speaker-test`.

	This was found here: https://stackoverflow.com/a/28995539

	From 466e0f57b15e11ab19af900341f98a726ad1bf73 Mon Sep 17 00:00:00 2001
	From: Sammy Pfeiffer <[email protected]>
	Date: Wed, 8 Sep 2021 16:06:44 +1000
	Subject: [PATCH] Apply https://github.com/PointCloudLibrary/pcl/pull/3853 from
	Davide Faconti to improve Voxelgrid runtime by 20% to 1.8.1 tag (backport)

	---
	filters/include/pcl/filters/impl/voxel_grid.hpp \| 7 +++++--
	filters/src/voxel_grid.cpp \| 6 ++++--
	2 files changed, 9 insertions(+), 4 deletions(-)

	#!/usr/bin/python2
	import rospy
	import rostopic
	import argparse
	import threading

	# Borrowed from https://chaonan99.github.io/2018/rostopic-republish/

	global g_msg
	g_msg = None

	function yawAngleFromQ(time, value, v1, v2, v3)
	M_PI = 3.14159265358979323846
	a = v1
	b = v2
	c = v3
	d = value

	aa = a * a
	ab = a * b
	ac = a * c