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Book about mages who can harvest magical energy from the environment What is a magic number, and why is it bad? Which SUSY models are affected by the recent LHCb result? Acro package provides "! Missing number, treated as zero." after update to acro-v2.7b Can anybody please help me to prove this:  Let $p$ be greater than or equal to $1$. Show that for the space $\ell_p=\{(u_n):\sum_{n=1}^\infty |u_n|^p&lt;\infty\}$ of all $p$-summable sequences (with norm $||u||_p=\sqrt[p]{\sum_{n=1}^\infty |u_n|^p}\ )$, there is an inner product $&lt;\_\,|\,\_&gt; $ s.t. $||u||^2=&lt;u\,|\,u&gt;$ if and only if $p=2$. Gradient of $a^T X b$ with respect to $X$ How can I find the gradient of the term $a^TXb$ where $X$ is a $n \times m$ matrix, and $a$ and $b$ are column vectors.  Since the gradient is with respect to a matrix, it should be a matrix.  But I do not have a clue on how to derive this gradient.   Any help ? Escape string for use in Javascript regex I'm trying to run a gunicorn_django process in supervisor but it always exits immediately, giving this error:   INFO exited: my_app (exit status 1; not expected) INFO received SIGCLD indicating a child quit INFO gave up: my_app entered FATAL state, too many start retries too quickly   My server script looks like this:  #!/bin/bash set -e LOGFILE=/var/log/gunicorn/my_app.log LOGDIR=$(dirname $LOGFILE) NUM_WORKERS=3 USER=my-www-user GROUP=my-www-user cd /home/my-www-user/my_app source /home/my-www-user/.virtualenvs/my_app/bin/activate test -d $LOGDIR || mkdir -p $LOGDIR gunicorn_django -w $NUM_WORKERS --debug \  --user=$USER --group=$GROUP \  --log-level=debug --log-file=$LOGFILE 2&gt;&gt;$LOGFILE\  --pythonpath=my_app --settings=settings.active \  my_app.wsgi:application   And my supervisor config looks like this:  [program:my_app] directory=/home/my-www-user/my_app/ user=my-www-user command=/home/my-www-user/my_app/server.sh stdout_logfile=/var/log/supervisor/my_app.log stderr_logfile=/var/log/supervisor/my_app-error.log autostart=true autorestart=true   When I su into the my-www-user account the server starts normally. When I do sudo supervisorctl start my_app it simply hangs until I do CTRL-c, then I find the error above in the supervisord.log file.  Does anyone have a clue about what I am missing? Query Which Profiles Have Read Access To Specific Object? Since I couldn't think of how to write this query off the top of my head, I thought it might be worth sharing. How can I query which Profiles have Read permission on a specific object? I knew it would have something to do with ObjectPermissions and PermissionSet, but had to look up the documentation for both to piece it together. What is the maximum length of a URL in different browsers? What is the maximum length of a URL in different browsers? Does it differ among browsers? Is a maximum URL length part of the HTTP specification? Taking the * of these two large shapefiles   locally using ArcMap takes appr. 10 min.   Over the last few weeks, I've tried to obtain the same results using other, open-source approaches without success. I am curious why only ArcMap seems to generate results in a reasonable amount of time without errors.   The approaches I've tried so far:  QGIS  The most straight-forward alternative. There are two "union" functions available in QGIS. One default (part of vector overlay), one based on SAGA. Both functions create the desired results on smaller samples but fail to run (or take forever) on my shapefiles. I tried running union for 30 minutes after which the progress bar was at appr. 4%    PostGIS  I've ingested the shapefiles on an AWS RDS instance running postGreSQL with PostGIS enabled. The approach is not so straight forward and requires a hideous long SQL query to obtain the same result. Most importantly, the query did not create a meaningful result on the full datasets. It did run properly on a sample though.   See separate question   CREATE TABLE test.sqlislelijk AS  -- input data with polys1 AS (   SELECT      pfaf_id as df1,     geom as g   FROM hybas06_v04 ), polys2 AS (   SELECT      aqid as df2,     geom as g   FROM y2018m11d14_rh_whymap_to_rds_v01_v01 ), -- intersections intersections AS (   SELECT df1, df2, ST_INTERSECTION(a.g, b.g) i, a.g AS g1, b.g AS g2    FROM polys1 a, polys2 b WHERE ST_INTERSECTS(a.g, b.g) ), -- per-row union of intersections with this row diff1 AS (   SELECT df1, ST_UNION(i) i FROM intersections GROUP BY df1 ), diff2 AS (   SELECT df2, ST_UNION(i) i FROM intersections GROUP BY df2 ), -- various combinations of intersections pairs AS (   SELECT df1, df2, i AS g FROM intersections   UNION ALL   SELECT      p.df1,     NULL,     CASE       WHEN i IS NULL THEN g        ELSE ST_DIFFERENCE(g, i)     END   FROM polys1 p LEFT JOIN diff1 d ON p.df1 = d.df1   UNION ALL   SELECT     NULL,     p.df2,     CASE       WHEN i IS NULL THEN g       ELSE ST_DIFFERENCE(g, i)     END   FROM polys2 p LEFT JOIN diff2 d ON p.df2 = d.df2   ) SELECT    df1 as pfaf_id,   df2 as aqid,   g as geom FROM pairs WHERE NOT ST_IsEmpty(g);   Google BigQuery  Google's GIS extension for BQ looks promising but I experienced weird behavior and internal errors, probably due to mixing of GEOMETRY and GEOGRAPHY objects. Also, the syntax is similar to PostGIS and a command of 1 line in geopandas takes >20 lines in SQL.   GeoPandas  Probably my favorite approach. The out-of the box approach does't give any results after running it for several hours. My latest approach includes tiling the shapefiles, use multiprocessing on each tile and merge them. Not very straight forward and one 10x10 degree tile till takes 40+ minutes to calculate.   See   It is the first time in my career that I am impressed by the performance of ArcMap. It seems that ArcMap handles this use-case much, much better than anything else. The issue seems persistent over all solutions I've tried so far. Is there something wrong in the underlying libraries of the open-source/alternative solutions?    Note that Union in ArcMap means something different than in the Shapely / PostGIS world. Openlayers v4.0.1 support Google Maps Javascript API? I want to know if the latest version of Openlayers (v4.0.1) supports Google Maps as a Tile Layer. I can't find any document ion about this. If Openlayers doesn't support Google Maps, could someone  tell me if there is any way to do this? Display command in xterm titlebar My Bash Prompt is currently setting the xterm titlebar using the following sequence:  PS1='\033]0;\u@\h&gt;\w\007'   Is there an easy way to display the current command in the titlebar. For example, if I am tailing a file using tail -f foo.log, I want my titlebar to say tail -f foo.log. Database schema documentation for the public data dump and SEDE Can't quantum teleportation be superluminal some percentage of times? I apologize if this is a really silly question.   In the (textbook) quantum teleportation algorithm, in the step right after Alice has measured her system but before she has sent her classical information to Bob, she is about to send one of the following values: 00,01,10,11.   What if Bob doesn't want to wait and simply takes a guess? Wouldn't there then be superluminal communication 25% of the time? Is there a word for a person who gives out too many extraneous details? Render turns out plain white For some reason, when I render out the image, it is plain white. I've checked the sky settings, and I tried applying textures, but nothing seems to change.  How can I fix this? Reduce file size without losing quality I would like to save files in Photoshop but keep them as small as possible.   I use Save for Web (and Devices) and save as a JPEG. Here are the settings I used:     I really do not want to lower the quality settings because I use text and sometimes I see artifacts if the setting is too low.   This produces file sizes of several hundred kilobytes depending on size of image. While this isn't a huge issue these images are used for the web and smaller is better. What are techniques without reducing quality to reduce the file size?   Update:  To add some more information here:   Many of the images I use and create get sent via email. This severally limits what I can do with placing of text using HTML and CSS over the image.   Also I use a variety of fonts. Some I could use for the web using CSS's @font-face but you can run into large file sizes and in some cases you cannot upload the font to the web legally. I could use a service like  but again many fonts I use are not available with Typekit.   Here is an example image: If $f$ is continuous with $f(x) = f(2x),f(1) = 3$, then what is $ \int_{-1}^{1}f(f(x))\,dx$? If $f(x)$ is a continuous function such that $f(x) = f(2x)$ and $f(1) = 3\;,$ Then $\displaystyle \int_{-1}^{1}f(f(x))\,dx$   $\bf{My\; Try::}$ Here $-\infty &lt;x&lt;\infty$ and Given $f(x) = f(2x)$  So Using Recursively $$\displaystyle f(x) = f(2^1x)=f(2^2x)=..........=\lim_{n\rightarrow \infty}f\left(2^{n-1}x\right)$$   OR we can write it as $$f(x) = f\left(\frac{x}{2}\right)=f\left(\frac{x}{2^2}\right)=........=\lim_{n\rightarrow \infty}f\left(\frac{x}{2^{n-1}}\right)$$  Now How can i prove that $f(x)$ is a constant function.  Help me  Thanks How does extra damage work for critical hits? I'm a bit confused on how extra damage works for critical hits. Let's take the following example: A thief with sneak attack rolls a crit. I'm under the impression he rolls double his normal attack damage dice AND double his Sneak Attack damage dice. Is this accurate? Another example, I finished DM-ing my first campaign recently. The Giant Spider enemy monster has an melee attack that causes a constitution saving throw. If the player fails, the enemy rolls an additional 2D8 of damage. In this situation, if there was a critical hit, and the player failed their saving throw, would I also roll double dice on the additional damage? Or is that considered a separate attack?