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Day: August 21, 2017

TensorFlow On The Pi

Published 2017-08-21 by Kevin Feasel

Pete Warden shows how to install TensorFlow on a Raspberry Pi:

It’s never been easy to get TensorFlow installed on a Pi though. I had created a makefile script that let you build the C++ part from scratch, but it took several hours to complete and didn’t support Python. Sam Abrahams, an external contributor, did an amazing job maintaining a Python pip wheel for major releases, but building it required you to add swap space on a USB device for your Pi, and took even longer to compile than the makefile approach. Snips managed to get TensorFlow cross-compiling for Rust, but it wasn’t clear how to apply this to other languages.

Plenty of people on the team are Pi enthusiasts, and happily Eugene Brevdo dived in to investigate how we could improve the situation. We knew we wanted to have something that could be run as part of TensorFlow’s Jenkins continuous integration system, which meant building a completely automatic solution that would run with no user intervention. Since having a Pi plugged into a machine to run something like the makefile build would be hard to maintain, we did try using a hosted server from Mythic Beasts. Eugene got the makefile built going after a few hiccups, but the Python version required more RAM than was available, and we couldn’t plug in a USB drive remotely!

Read the whole thing, even if for the science experiment aspect.

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Compacting Shared Libraries In R

Published 2017-08-21 by Kevin Feasel

Dirk Eddelbuettel compacts the tidyverse:

Of course, there is a third way: just run strip --strip-debug over all the shared libraries after the build. As the path is standardized, and the shell does proper globbing, we can just do

$ strip --strip-debug /usr/local/lib/R/site-library/*/libs/*.so

using a double-wildcard to get all packages (in that R package directory) and all their shared libraries. Users on macOS probably want .dylibon the end, users on Windows want another computer as usual (just kidding: use .dll). Either may have to adjust the path which is left as an exercise to the reader.

When running this against the tidyverse library, shared library sizes dropped from 78 MB down to 6.6 MB.  Not bad for a single command. H/T R-Bloggers

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Cross-Container Transactions With Memory-Optimized Objects

Published 2017-08-21 by Kevin Feasel

Ned Otter continues his series on In-Memory OLTP isolation levels:

Why will it fail?

It will fail because the initiation mode of this transaction is not autocommit, which is required for READ COMMITED SNAPSHOT when referencing memory-optimized tables (the initiation mode is explicit, because we explicitly defined a transaction).  So to be totally clear, for queries that only reference memory-optimized tables, we can use the READ COMMITTED or READ COMMITTED SNAPSHOT isolation levels, but the transaction initiation mode must be autocommit. Keep this in mind, because in a moment, you’ll be questioning that statement….

There are some interesting implications that Ned teases out, so I recommend giving it a careful read.

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A dplyr Quiz

Published 2017-08-21 by Kevin Feasel

John Mount wants to know how well you understand dplyr:

dplyr is one of the most popular R packages. It is powerful and important. But is it in fact easily comprehensible?

dplyr makes sense to those of us who use it a lot. And we can teach part time R users a lot of the common good use patterns.

But, is it an easy task to study and characterize dplyr itself?

Take John’s quiz and find out.  He wasn’t kidding about it being an advanced quiz.

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Basics Of Dplyr

Published 2017-08-21 by Kevin Feasel

Dave Mason is dipping his toes into the R waters:

I think my first exposure to R was at PASS Summit 2016. Since then, I’ve made an effort to attend R sessions at SQL Saturdays. The one commonality I seem to find in all of them is a demo with (or mention of) the dplyr package. It’s a package of functions that manipulate data in data frame objects (think of them as SQL Server/relational tables…or if you’re a .NET developer, a System.Data.DataTable object). R feels inexorably tied to dplyr at this early stage for me. R is probably way more vast than I realize, but what would it be without dplyr? Would it still be as popular? Would it still be as powerful?

What’s It Good For

I’m not sure if I’m perceiving this the right way yet, but dplyr sure feels a lot like LINQ, a .NET Framework technology that provides query-like capability for C#. For instance, you can select a subset of objects from an array, sort them, find a minimum or maximum, etc. It’s kind of like querying SQL Server, just without SQL Server.

I like the comparison of dplyr against LINQ, as they’re both data querying and transformation tools whose motif is a series of functions chained together.

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Powershell: Text Search In A Table Value

Published 2017-08-21 by Kevin Feasel

Shane O’Neill clarifies a misunderstanding in Powershell:

and you are running the following PowerShell command to check if the results contain a value…

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$String = "abc"
$Array = @(Invoke-Sqlcmd -ServerInstance "SQLServer" -Database "Database" -Query "SELECT code FROM dbo.users")
$Array.Contains($string)

It will return FALSE.

Now we know that the FALSE is false because we know that the string is in there!
This code is proven to work with arrays as stated here by the “Hey, Scripting Guy!”s so this was getting filed under “WTF PowerShell”

It’s a good post, so check it out and remember that DataRows aren’t strings.

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Getting Started With SQL Server For Free

Published 2017-08-21 by Kevin Feasel

Jeff Mlakar points out some free resources for getting started with SQL Server:

The basics of the “Learn SQL Server Starter Pack”:

  1. SQL Server 2016 DE
    1. You can get the Developer Edition (DE) for…wait for it…FREE!
    2. Out in the wild you’ll see mostly Standard Edition (SE) or Enterprise Edition (EE). The great thing about DE is that it is identical to EE (it has all the features) in every aspect except that it cannot be licensed on a production machine. It must only be used for TEST or DEV environments. For home lab purposes you can use it as your development environment and have access to all the features to learn on!
    3. Download it here – SQL Server Downloads
    4. While you are here get used to reading the release notes and what is new in the version. You don’t need to understand everything in here right away but get used to the jargon and how Microsoft describes their features.
  2. Windows Server 2016 Evaluation Edition
    1. Download Windows Server 2016 Evaluation Edition
    2. You can evaluate the software for 180 days then will need to activate it. Then you can try to register for another eval and try again
  3. Virtual Box
    1. Virtual Box is a free, simple, and reliable virtualization tool. You’ll be able to do a lot to get started and build up your virtualization knowledge with this.
    2. Download the latest version of Virtual Box
    3. You don’t need to know very much about hypervisors and such – Virtual Box is very easy to learn with good documentation.

Evaluation versions are good for learning because they force you to tear down and rebuild your environment!

Jeff then links to a number of free resources to help out with the learning experience.

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