Coding Memo Pad

[codingmemos]

Replace expressions like O_2h[i÷2,j÷2] and O_2h[(i+1)÷2,(j-1)÷2] with O_2h[idx(i),idx(j)] and O_2h[idx(i+1),idx(j-1)], respectively:

s/O_2h\[\(.*\)÷2,\(.*\)÷2\]/O_2h[idx(\1),idx(\2)]/g

After running the above, get rid of repeated parens (transform expressions like idx((i+1)) into expressions like idx(i+1)) using:

s/((\([ij][\+\-][1]\)))/(\1)/g

[codingmemos]

Globbing files with multiple extensions in Z shell

Suppose I want to glob files that live in either dirA or dirB, and end with either .ppm or .png. At least in Z shell, I can glob as follows:

dirA/*.(ppm|png) dirB/*.(ppm|png)

Furthermore, I can accomplish the same by doing the following:

(dirA|dirB)/*.(ppm|png) dirB/*.(ppm|png)

Credit to Nacho Caballero's blog post on Z shell usage.

[codingmemos]

ImageMagick image stack example

Below is an example of use of the image stack in ImageMagick. On Unix/Linux, run the following command stack_test.png):

magick logo: \( -size 320x28 xc:white -gravity center -pointsize 14 -fill black -annotate +0+0 "A_TEXT" -rotate 30 \) +append stack_test.png

The above command appends some rotated text to the left of a (built in) image of the ImageMagick wizard. I got the text rendering snippet from fmw42′s post on the ImageMagick forums. The result is below:

What if we want to generate two text labels and append them into a single image? We can run the command below:

magick \( -size 100x28 xc:white -gravity center -pointsize 14 -fill black -annotate +0+0 "FOO" \) \( -size 100x28 xc:white -gravity center -pointsize 14 -fill black -annotate +0+0 "BAR" \) +append append_multi_text_test.png

And the result we get is as follows:

[codingmemos]

Measure time taken to render frame in ParaView

In the ParaView python shell (View > Python Shell), type:

import time

Then, to measure the time taken to render, use:

start=time.clock(); Render(); end=time.clock(); print(end-start);

Credit to Yevgen Yampolskiy's StackOverflow post for timing functions in Python.

[codingmemos]

In practical terms, the main principle of RAII is to give ownership of any heap-allocated resource—for example, dynamically-allocated memory or system object handles—to a stack-allocated object whose destructor contains the code to delete or free the resource and also any associated cleanup code.

Microsoft’s cpp-docs on Smart Pointers

[codingmemos]

Vulkan Tools

RenderDoc

Gapid

[codingmemos]

Pretty code snippets on Tumblr

Edit the HTML of your Tumblr theme and include Google’s code-prettify script:

<script src="https://cdn.rawgit.com/google/code-prettify/master/loader/run_prettify.js"></script>

Inside the <style scoped="scoped"> tag, add the following:

pre { overflow-x: auto; white-space: pre; }

Setting white-space to pre ensures that text only wraps at explicit line breaks. Setting overflow-x to auto tells the browser to draw a scroll bar only when the text “overflows at the left and right edges”.

[codingmemos]

Profiling memory usage over time with ps

while true; do ps -C <command_name> -o pid=,rss=,vsz= >> /tmp/mem.log sleep 1 done &

Note that rss is short for "resident set size", which is "the non-swapped physical memory that a task has used" in KiB. vsz is the "virtual memory size of the process" in KiB. (Quotes from the ps man page.)

This was adapted from LovesTha's StackOverflow post.