Saturday, April 25, 2015

Value Never Used – Or Is It?

Sometimes, dcc32 is just plain stupid …

I have this code in the OmniThreadLibrary:

function TOmniThreadPool.Cancel(taskID: int64): boolean;
res: TOmniWaitableValue;
{$IF CompilerVersion >= 22}
Result := false; // not really used
res := TOmniWaitableValue.Create;
otpWorkerTask.Invoke(@TOTPWorker.Cancel, [taskID, res]);
Result := res.Value;
finally FreeAndNil(res); end;

The IFDEF part is there because otherwise compiler complains about result being potentially undefined.

[DCC Warning] OtlThreadPool.pas(1315): W1035 Return value of function 'TOmniThreadPool.Cancel' might be undefined

I’ve first observed this with the XE and it was fixed after the XE2 (can’t repeat this with XE8, but I didn’t check every compiler inbetween.)

Friday, April 17, 2015

New Home for OmniThreadLibrary

OmniThreadLibrary has been moved from Google Code to GitHub.

I still have to move existing issues as they were not moved automatically.

Thursday, April 16, 2015

New Home for My Units

My collection of open-sourced units has been moved from Google Code to GitHub.

Wednesday, April 08, 2015

XE8 is out …

… and OmniThreadLibrary works fine with it. (That’s it. Just wanted to let you know.)

Friday, April 03, 2015

Runtime SQL Query Builder

I don’t want to use long SQL strings in the code.


Firstly, it is a pain to write long multiline strings in Object Pascal. (Embarcadero, are you listening? Can we please get multiline strings in Delphi? Please?)

Secondly, I’m very OCD when it comes to compiler watching my every step. I absolutely hate runtime errors and I want every problem to be detected during the compilation. That includes typos in database field names and changes attributed to the entropy (i.e. changes in the database structure).

On a tangent, that’s why we are creating and managing tables and databases in the code. We have all fields defined as constants, all SQL statements created in runtime and everything stored under version control.Upgrading a database to a version required by the program is therefore a very simple operation. (Downgrading is still a problem. Downgrading is hard.)

Thirdly, concatenating query strings together when you are dynamically building a query string based on the conditions in the program is a mess.

That’s why long years ago I created a simple runtime query builder. It was dormant (in the “good enough for me” state) for a long time but recently I required more functionality from it and I extended it further. It is now in a state which may be useful for somebody else but me so I’m releasing it as an open source under a BSD license.

For impatient: Get GpSQLBuilder on GitHub.

Thursday, March 19, 2015

Unit Testing Recap & Downloads

The Unit Testing workshop was pretty much full.

2015-03-19 11.06.12

It was good to see that many interested Delphi programmers in one room. Thanks for coming, everybody!

The downloads for the workshop are now online.

Thursday, March 12, 2015

What’s New in Delphi XXXX

A great list of “What’s new” for Delphis from 3 to XE7 can be found on StackOverflow.

(just noticed and thought I’d better pass this on)

Wednesday, March 11, 2015

Unit Testing, Mocking, Inversion of Control

On March 19th (that’s next Thursday), I’ll be leading a workshop dedicated to unit testing Delphi programs. We’ll start with basics and and cover different tools (DUnit, DUnit2, DUnitX, TestInsight) and different programming methodologies.

Register here.

Sunday, March 01, 2015

OmniThreadLibrary 3.04

OmniThreadLibrary 3.04 is now released. Get it here or check out the release-3.04 tag (or just follow the trunk, which is the best way to experience the OmniThreadLibrary).

Some other links you may need:

Home page:
Google+ community:
Issue tracker:
SVN checkout instructions:
Author's blog:
Author's home page:
Documentation wiki:
Documentation book:


New features

  • Implemented simple and fast Parallel.&For which supports only integer ranges.
  • Implemented Parallel.Map.
  • Added overloaded Execute methods to IOmniParallelInitializedLoop and IOmniParallelInitializedLoop<T> so that IOmniTask parameter can be passed to the executor.
  • Implemented Run overloads that internally call Invoke to start thread worker.
  • Implemented TOmniValue.HasArrayItem.
  • Implemented TWaitFor which supports waiting any/all and is not limited to 63 objects.
  • IOmniTaskControl can wait on any number of comm handles and wait objects. That enables support for >60 tasks in the OtlThreadPool.
  • Implemented TOmniBlockingCollection.ToArray<T>.
  • NumTasks parameter (OtlParallel) can be negative. In that case, specified number of cores will be reserved for other purposes and all other will be used for processing.
  • Example: If NumTasks(-2) is used when process has access to 8 cores, 6 of them (8 - 2) will be used to run the task. 
  • Removed project groups.
  • Tested with 2007-XE7.

Bug fixes

  • Fixed race condition in IOmniPipeline termination code [tnx to Dean Hill].
  • Creating parameters with the array overload (IOmniTaskControl.SetParameters(['From', 0, 'To', 99])) was not working.
  • Fixed problems in demos 33_BlockingCollection and 47_TaskConfig.

New demos

  • 55_ForEachProgress: Demonstrates progress bar updating from a ForEach loop.
  • 56_RunInvoke: Simplified 'run & invoke' low-level API.
  • 57_For: Simple and fast parallel for.
  • 58_ForVsForEach: Speed comparison between Parallel.ForEach, Parallel.For, and TParallel.For (XE7+).
  • 59_TWaitFor: Demo for the new TWaitFor class.
  • 60_Map: Demonstrates the new Parallel.Map abstraction.
  • 61_CollectionToArray: Demonstrates the new TOmniBlockingCollection.ToArray<T> method

Wednesday, February 18, 2015

OmniThreadLibrary 3.04 Release Candidate

RC for the new OmniThreadLibrary release is available here.

This version should work with Delphis from 2007 to XE7. Win32 and Win64 are supported for Console and VCL applications.

Tuesday, February 03, 2015

Converting Collection to an Array

Blocking collections (IOmniBlockingCollection) are basic elements for data storage and transfer in many high-level OmniThreadLibrary abstractions. They can, however, be somewhat clumsy when you want to read data from them, as there is no indexed access, just the basic “give me next element” enumeration.

To help a bit, SVN now includes three new class functions in the TOmniBlockingCollection class – ToArray<T>, ToArrayIntf<T>, and ToArrayRec<T>.

class function ToArray<T>(coll: IOmniBlockingCollection):
class function ToArrayIntf<T: IInterface>(
IOmniBlockingCollection): TArray<T>;

class function ToArrayRec<T: record>(
IOmniBlockingCollection): TArray<T>;

Friday, January 30, 2015

Parallel Map

At my latest parallel programming presentation a participant suggested that I should extend the OmniThreadLibrary with a parallel mapping abstraction. Dear sir, here is a gift for you.

numbers: TArray<integer>;
odds : TArray<string>;
//initialize the `numbers` array (not shown)
odds := Parallel.Map<integer,string>(numbers,
function (const source: integer; var dest: string): boolean
Result := Odd(source);
if Result then
dest := IntTostr(source);
//do something with the `odds` array (not shown)

Saturday, January 10, 2015

Implementing Record Assignment Operator [2]

Yesterday I hinted at having a working (and easy to use) solution which allows you to detect a record assignment (or copying, if you want) and to access both records (left and right part of the assignment operation). You can also modify record data when an assignment is detected. I also mentioned that my approach is very ugly, unstable, likely to cause problems in future Delphis and so on. You should read this article for the technical details, not to really use my code in an application. You have been warned!

Before I jump to hardcode Delphi stuff, I’d like to mention few different approaches that various smart people have already implemented. Most of them slipped below my radar in the past – and I’m guessing this may be the case for you too – so I’m listing them here in case you want to do more research on the topic.

Friday, January 09, 2015

Implementing Record Assignment Operator [1]

Following the yesterday’s hunch, I did some research and I came up with a way to detect when a record is copied (simple, supported, working everywhere) and even to access both records (source and target) during that operation (unsafe, unsupported and currently working only for Win32).

Now I can write such code:

Thursday, January 08, 2015

Implementing Destructor for a Record

Smart records in Object Pascal are very nice, but they have a stupid limitation – you cannot implement a destructor for a record.


A solution for that is quite simple and can be found all over the internet – add an interface to this record and implement the cleanup in this interface. To make it even simpler, you can use the IGpAutoExecute interface from the completely free GpStuff unit.

Thursday, December 25, 2014

Blast from the past: Turbo Pascal raytracer

Paweł’s recent post reminded me of a veeeeeery old raytracer I wrote in years 1985/89. (Yes, young ones, we had computers then!)

Header states:

  Computer: VAX-11/750
  Language: Pascal V2
  Graphics: VT100

  Computer: IBM-PC
  Language: Turbo Pascal 4.0
  Graphics: EGA 640 x 350 x 16

  Computer: IBM-PC/AT
  Language: Turbo Pascal 5.0
  Graphics: VGA 800 x 600 x 256

Quite a blast from the past – the 800 x 600 in 256 colors (out of a great palette of 262144 colors!) was more or less the greatest graphic card which you could get for PC at that time. And the first version was running on a VT100 terminal with an additional graphics board. Sadly, I don’t have that code anymore :(.

Saturday, December 13, 2014

Attribute-based Command Line Parsing

Oh, command line parsing, the old enemy of mine!

imageIn ye olden days, when I was learning Pascal, I did some programming on VAX/VMS systems, where you could (and should) leave the job of command line parsing to the DCL – the command line interpreter (something like CMD.EXE on Windows). You just wrote a definition file (see example on the right, found on the web) and DCL did the rest.

Since those days I hated that I have to parse command line programmatically. Sure, there were parsing libraries – and I wrote few of them myself – but I was never happy with them. There was always too much code to write.

Then I was looking for good examples on using attributes in Delphi and suddenly it occurred to me that I could use them for command line parsing, too! And that’s how GpCommandLineParser was born.

Before continuing, I should mention that I have based it (concept-wise, implementation is all my own) on the CommandParser unit, which comes with Delphi and can be found in Samples\Object Pascal\Database\dbExpress\Utils. This is a very nice but mostly unknown command line parser which I can definitely recommend.

Thursday, November 27, 2014

OmniThreadLibrary 3.04 beta 1 – testers needed

I have (finally!) implemented support for more than 60 simultaneous tasks in the OTL thread pool and for more than 60 waitable events in the IOmniTaskControl. This also enables support for massively parallel execution in OtlParallel abstractions. IOW, Parallel.ForEach will run correctly on machines with 64 and more cores without needing to call NumTasks(60).

I’ve been testing this change and I think that it’s working correctly, but it is a big (and potentially dangerous) modification and so I’d like to see additional testers trying the new version in real programs before I submit it to the SVN.

So – if you like to live on the edge, if you’d like to help improve OTL and especially (but not required!) if you can test the code on a machine with 64 or more cores, please download the 3.04b1 from Dropbox and try it out. You can post reports here or send them to my email (my address is in the header of every OmniThreadLibrary file). In case of a problem, a short, repeatable, self-contained example will be of an immense help.


Wednesday, November 26, 2014

Parallel programming with XE7–reminder

A note for Slovenian readers.

Ne pozabite – jutri bom predstavil novo knjižnico System.Threading, ki olajša razvoj hitrih in odzivnih programov za vse platforme, ki jih podpira RAD Studio – Windows, OS X, iOS, Android – ter v obeh programskih jezikih – Delphi in C++. Ogledali si bomo tudi novosti v knjižnici OmniThreadLibrary.

Za več podatkov in prijavo kliknite tu!

Wednesday, November 12, 2014

Pohitrite programe z RAD Studiom XE7

This is an invitation for the XE7 workshop in Slovenia which is targeted at Slovenian programmers.

RAD Studio XE7 prinaša nov način paralelizacije programov. S kodo, zbrano v enoti System.Threading lahko na enostaven način pohitrite nekatere funkcije v programih, tako da se izvajajo sočasno z drugo kodo. Še lepše - System.Threading deluje na vseh podprtih platformah, torej poleg Windows tudi na OS X, iOS in Androidu. Na delavnici si bomo podrobno ogledali nove načine paralelizacije in pregledali druge knjižnice, ki podpirajo hkratno (paralelno) izvajanje v okolju Windows.

Predavanje bo v četrtek, 27. novembra, 2014.

Kliknite za prijavo

Wednesday, October 29, 2014

DAPUG 2014 Workshop

Presentations and code samples from DAPUG 2014 workshop are now available online.

Big thanks to organizers (and especially Jens) – we had great time in Denmark! Hope to see you again some time!

Tuesday, October 21, 2014

DAPUG workshop

Hesselet hotel is very nice and workshop is proceeding smoothly.


Just saying :)

Monday, September 29, 2014

Fixing XE7 + Android SDK 23 ZipAlign Problem

If you install RAD Studio XE7 and then upgrade Android SDK to version 23, you won’t be able to deploy applications to Android devices anymore.


The reason for that is that ZipAlign.exe was moved out of sdk\tools folder in SDK 23 and XE7’s deployment process cannot find it anymore. Now it is located in sdk\build-tools\20.0.0, but only is Android SDK Build-tools rev. 20 are installed, which doesn’t happen automatically.


To fix my Delphi I first had to install Build tools rev. 20. Then I copied sdk\build-tools\20.0.0\zipalign.exe to sdk\tools\zipalign.exe. That fixed the deployment problem.

I’m hoping Embarcadero will fix this in the next update, but for now you can use this workaround.

[Android sdk folder can be found in c:\Users\Public\Documents\Embarcadero\Studio\15.0\PlatformSDKs\adt-bundle-windows-x86-20131030\sdk]

Tuesday, September 23, 2014

Delphi programmer wanted

This is a job offer for a full time programming job in Ljubljana.

Iščemo Delphi programerja za dolgotrajno razmerje; človeka, ki se ne ustraši stare kode in z veseljem programira s sodobnimi orodji. [XE2, prehod na sodobno različico je že v teku in ga bo pomagal zaključiti prav programer ali programerka, ki ga iščemo.] Delo se opravlja v pisarni v Ljubljani.

Več o podjetju: Kontakt: primoz (pri)

Thursday, September 18, 2014

Users Like FireUI and Dynamic Arrays

A snapshot from the XE7 presentation in Ljubljana.


Highlights of the presentation were FireUI, System.Threading, dynamic arrays, and OmniXML.

‘Twas a very nice crowd, asking LOTS of questions. It was also good to see some young(er) people and some Delphi [insert a prehistoric version here] users who finally decided that they should upgrade.

Monday, September 08, 2014

RAD Studio XE7 Launch in Slovenia

If you want to see all the great new stuff in XE7, join me on Wednesday, 17th in Ljubljana. We’ll cover the new VCL stuff, multithreading support, improvements for multi-device development, business mobile services and more.

As usual, presentation will be in Slovenian language.

More information & registration

Monday, September 01, 2014

Chromecast Randomly Crashing–Solved!

This is one of rare posts on my blog that doesn’t cover pascal programming. Proceed on your own risk ;)

For the last half a year, I’ve been a happy owner of a Chromecast device. Great stuff, especially as it allows me (with a small hack) to watch Netflix on my TV and listen to Pandora. At the beginning, it was a bit unstable, but through regular updates it stabilized quite a bit – until build 17977 got installed.

Since that time I got random crashes while playing any media (video or audio) from any source (in-house or external provider). It would load the player app, start playing, then crash after a few seconds. It would work fine for days, even weeks, but then it would start crashing and I would not be able to use for for half a day, after which it would start working again.

I’ve decided that the hardware is broken, maybe overheating, and I bought another one. (Did I mention it’s cheap?) But no luck – it started behaving the same as soon as it has upgraded to build 17977.

Few days ago I found a network forum thread where someone (sorry, no link, it got lost) mentioned a possibility of a bad power source. (My Chromecast is plugged into TV’s USB port.) And when the device started playing tricks on me today, I plugged it into an external USB power supply. And – surprise, surprise – it started working!

Something weird is still going on. When I start playing in a new player (i.e. when I switch apps), media is played for few seconds, then the TV goes blank and its power light starts blinking, then the picture reappears and media continues to play.

My current guess is that Chromecast does something weird which basically quick-resets the TV. When Chromecast was plugged into TV’s USB port, that also reset the Chromecast, but now that it’s plugged into an external power source, Chromecast continues playing while the TV does its yoyo trick.

I’m not completely satisfied with this solution as I would rather see my Chromecast to turn off together with the TV, but it is a “good enough” workaround. I still love that device, though. It’s the best stuff Google made in a long long time.

I’m posting this blog in hope that it will help other Chromecast users who may run into the same problem.

Tuesday, August 26, 2014

The Denmark Workshop is Filling Up

If you are still deciding whether to attend my workshop, you should hurry up. The organizers have notified me that there are only few places left as there are some physical constraints they have to observe, namely how many people fit in the conference room ;)

BTW, if you are interested in the parallel part of the workshop, you’ll be glad to know that I’ll also be covering the new cross-platform multithreading support in XE7.

Wednesday, August 06, 2014

Workshop in Denmark

DAPUG, the Database Application Programmers Users Group (aka Danish Embarcadero User Group) is one of Delphi user groups which organizes great events twice a year. I’m very proud that they have invited me to speak in October, even though I’ll miss ITDevCon because of that :(

(A note to ITDevCon organizers – DAPUG’s autumn workshop is traditionally organized near the end of October.)

Multithreading, regular expressions and attributes, oh my!

First day will be completely dedicated to multithreading. We’ll start with basics – why and how – and proceed with TThread-based multithreading on all supported platforms. After lunch we’ll focus more on high-level multithreading with the open-sourced OmniThreadLibrary.

A note to participants: I’ll be presenting multiple small problems for you to solve during the workshop. At least you should have Delphi installed on the computer (for best experience it should be one of the latest versions). If you really want to come prepared, you can also preload OmniThreadLibrary and if you are trying for the best in class award ;) you can read all about high-level multithreading in advance on the OmniThreadLibrary wiki.

The second day will be organized around three topics – attributes, regular expressions and continuous integration. The common point is productivity – in the first two sessions I’ll be showing you how to use some of the incredible power of Delphi to simplify your programming life and in the latter I’ll be focusing on the last stage of any application – building and deploying the release version.

See you there!

Workshop will be held on October 21st and 22nd in Hotel Hesselet in Nyborg.

More information and registration form can be found here.

Saturday, July 12, 2014

Smart Mobile Studio 2.1 (beta 1) is out!

If you need to write software for phones/browsers/node.js/microcontrollers, you should check out the new Smart Mobile Studio 2.1 (beta 1). The list of new and fixed features is much too long to list here so I’ll just focus on the most important additions.

  • Integrated debugger!

  • Dockable IDE with support for multiple layouts.

  • Configurable keyboard shortcuts.

  • Split view mode shows code and design side-by-side.

  • Support for with statement in a clean, non-Delphi way.
    with p := something do begin
      // do anything with p
  • Optimizations and bug fixes in the compiler.
  • Built-in browser uses Chromium CEF3.

Thursday, July 10, 2014

Incrementing Progress Bar from a ForEach Loop

A deceptively simple question – how do you update a progress bar from a ForEach loop – popped up on the Google+ OmniThreadLibrary community. The implementation turned out to be quite tricky so I created an example (55_ForEachProgress) which is now part of the OmniThreadLibrary SVN repository.

The starting point was a simple Parallel.ForEach loop which I further simplified in the demo.

procedure (const task: IOmniTask; const i:
// do some work

// update the progress bar - how?

We cannot simply update the progress bar from the ForEach executor as that code executes in a background thread and one must never ever access VCL GUI from a background thread! It is also no good to send “please update” Windows messages to main thread as Parallel.ForEach is by default blocking – it waits for all workers to stop working – and messages won’t be processed during ForEach execution.