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import numpy as np

def extract_block_diagonal_blocks(A):
    assert A.shape[0] == A.shape[1], "matrix A should be square"

    N = A.shape[0]

    A_mirrored = A + A.T   # make the matrix symmetric so we only have to check one triangle

    blocks = []

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Linux installation notes

A giant ball of yarn containing notes on how to set up Debian/KDE Linux, with tips on useful software and commands.

Increase console font size

setfont /usr/share/consolefonts/Lat7-Terminus28x14.psf

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#!/bin/bash

# I do not want my screensaver to auto-activate after a timeout.
# For some reason, you *have* to select a nonzero, finite timeout value for xscreensaver (there's no "infinity").
# I only want my screensaver to active when I lock my system by pressing [Meta]+[L].
# This hotkey is set up to launch this script, which 
# - starts the xscreensaver daemon,
# - activates the screensaver (with lockscreen enabled),
# - waits for it to terminate (unlocking logs an "UNBLANK" event),
# - then kills the xscreensaver daemon.

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Connect an IP camera via wired ethernet to an ethernet USB adapter to a Raspberry Pi

Connect the camera to the ethernet USB adapter via a CROSSOVER cable (or via an ethernet switch).

Install DHCP server:

sudo apt install isc-dhcp-server

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From InkScape to DXF

1. Save in Inkscape as PDF

Draft your design in InkScape. If there's any text, convert it to a path before or during exporting (Path → Object to Path).

Save as PDF (tested PDF v1.5).

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// Beveled wedge shape for OpenSCAD

// Written by C.A.P. Linssen <charl@itfromb.it>, Sept 2018

// This software is distributed under the "CC0 1.0 Universal (CC0 1.0)" license.

// You should have received a copy of the CC0 Public Domain Dedication along with this software. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.


// module bwedge

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ltspice options for high precision simulation/data export

Uses backward Euler integration (maxord=1 option), which can be very slow.

Set maximum iteration counts: DC iteration count limit (itl1, default: 100), DC transfer curve iteration count limit (itl2, default: 50), and transient analysis time point iteration count limit (itl4, default: 10) [ltwiki]_.

.OPTIONS maxord=1

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GPIB interfacing using Agilent 82357B on Ubuntu Linux

I initially had some problems installing on my laptop, so decided to boot Ubuntu 12.04.5 LTS, 3.13.0-32-generic from USB and work from there.

For an automated installation script, see gpib_install.sh (and gpib.conf) below. The rest of this document describes the actions of the installation script step-by-step.

First, get the packages that are necessary to support Python bindings:

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