The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Software Development’ Category

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The red zone, is why you want immutable constructs

Posted by jpluimers on 2019/05/23

Most code I come across is in the red zone, exactly depicting why you want immutable constructs. Immutable constructs will never end-up in the red zone.

Image: [WayBack] Wayback Machine.

The red zone is just one quadrant on the mutability/shareability diagram and getting outside that red zone quadrant is key.

With processor cores now becoming ubiquitous: you cannot get outside of the “Shard” half, so you have to get outside of the “Mutable” half.

Explaining the why and how, is part of a few presentations that Kevlin Henney gave:

Related YouTube videos are below.

–jeroen

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Posted in Conference Topics, Conferences, Development, Event, Multi-Threading / Concurrency, Software Development | Leave a Comment »

Scheduled jobs and jitter…

Posted by jpluimers on 2019/05/23

Too bad G+ doesn’t allow the WayBack machine or Archive.is to archive the whole thread at [WayBack] [Archive.is] Das es inzwischen fast überall Standard ist die Uhren mit einem guten Zeitsignal zu synchronisiseren (NTP, DCF-77, GPS etc) ist eigentlich eine gute Sache… – Kristian Köhntopp – Google+ so here are a few quotes below.

The generatel conclusions seem to be that:

This was the start:
Nils Ketelsen originally shared:

Guckt man live sieht es schon anders aus: Während die RunQueue meist so bei 4-5 liegt (bei 21vCPUs kein Problem) springt sie jede volle Minute einige Sekunden lang auf 20. Bei durch 2 Teilbaren Minuten auf ca. 40. Bei durch 10 Teilbaren Minuten auf 70, bei durch 15 teilbaren Minuten auf 150…. Ich habe eben durch einen schlecht getimten Toilettenbesuch die volle Stunde verpasst, das muss ich gleich mal anders hinbekommen, aber ich gehe davon aus, daß es da noch schlimmer ist.

And these some of the comments:

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Posted in *nix, *nix-tools, Algorithms, cron, Development, Power User, Software Development | Leave a Comment »

Useful settings for FastMM4 to tracking bottlenecks in multi-threaded memory allocation

Posted by jpluimers on 2019/05/23

Interesting thread that reminded me of the relatively new FastMM feature to track down lock contention and cope with it using release stacks:

[WayBack] I try use FastMM4 to tracking bottleneck in allocating memory. I was inspired by this Primož movie: https://www.youtube.com/watch?v=p-5mJyXvmrc When I… – Jacek Laskowski – Google+

The changes by Primož have added these two new conditional defines to the FastMM4 codebase:

These options are mutually exclusive.

This was the original post it got introduced in [WayBack] The Delphi Geek: Finding Memory Allocation Bottlenecks with FastMM4 and merged into the main repository.

FastMM introduction: [WayBack] The New Memory Manager In BDS 2006 – by Pierre le Riche.

It also taught me about [WayBack] RAMDisk – Software that Accelerates, Protects, Optimizes – Server Memory Products & Services – Dataram.

Primož stores his DCU files there: much faster than SSD, and far less wear on your SSD; see https://youtu.be/p-5mJyXvmrc?t=2675

–jeroen

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Posted in Conference Topics, Conferences, Delphi, Development, Event, FastMM, Software Development | Leave a Comment »

sql – How to Select Every Row Where Column Value is NOT Distinct – Stack Overflow

Posted by jpluimers on 2019/05/22

Since I always forget that IN and EXISTS have very different performance characteristics: [WayBack] sql – How to Select Every Row Where Column Value is NOT Distinct – Stack Overflow

Less slow

select emailaddress,customername from customers where emailaddress in
(select emailaddress from customers group by emailaddress having count(*) > 1)

Slow

select emailaddress,customername from Customers a where exists
(select emailaddress from customers c where a.customerName != c.customerName and a.EmailAddress = c.EmailAddress)

–jeroen

Posted in Database Development, Development, Software Development, SQL | Leave a Comment »

Insentricity :: Kermit on the JAIR 8080 ::

Posted by jpluimers on 2019/05/22

Cool: [WayBack] Insentricity :: Kermit on the JAIR 8080 ::

Repository: [WayBack] FozzTexx/Kermit-CPM: Columbia University’s Kermit for CP/M

–jeroen

Posted in Assembly Language, Development, History, Software Development | Leave a Comment »

web services – Accessing the original TWebRequest object in a Delphi SOAP Server – Stack Overflow

Posted by jpluimers on 2019/05/22

Thanks Ondrej Kelle for answering this:

uses
  System.SysUtils,
  Web.HTTPApp,
  Soap.WebBrokerSOAP;

function TTest.CallMe: string;
var
  WebDispatcher: IWebDispatcherAccess;
begin
  Result := '';
  if Supports(GetSOAPWebModule, IWebDispatcherAccess, WebDispatcher) then
    Result := Format('You are calling me from: %s', [WebDispatcher.Request.RemoteIP]);
end;

Source: [WayBack] web services – Accessing the original TWebRequest object in a Delphi SOAP Server – Stack Overflow

–jeroen

Posted in Conference Topics, Conferences, Delphi, Development, Event, Software Development | Leave a Comment »

It was all Greek to me: Iota · golang/go

Posted by jpluimers on 2019/05/21

Context is king!

Being Dutch, my association with iota was the phrase “Ik snap er geen iota van” (English: “It’s all Greek to me”), basically indicating iota is extremely small, similar to [WayBack] Iota | Definition of Iota by Merriam-Webster:

1: an infinitesimal amount : jot  (did not show an iota of interest)
2: the 9th letter of the Greek alphabet — see alphabet table

But the first time, I saw iota used in golang, I actually confused it with [WayBack] itoa – C++ Reference, because I am more than slightly wordblind.

So code like this was all Greek to me at first, not understanding the conversion from integer to ASCII**, and slightly later, not understanding iota to be extremely small either. Heck, its usage indicates it is small from infinitesimal:

const (
    _           = iota // ignore first value by assigning to blank identifier
    KB ByteSize = 1 << (10 * iota)
    MB
    GB
    TB
    PB
    EB
    ZB
    YB
)

So it took me a bit of thought to realise that it actually had to mean something completely different, so I found

It makes me wonder why they named it like this.

Slightly related:

–jeroen

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Posted in C++, Development, Go (golang), Software Development | Leave a Comment »

draft-ietf-appsawg-http-forwarded-10 – Forwarded HTTP Extension (X-Forwarded-For, X-Forwarded-By, and X-Forwarded-Proto)

Posted by jpluimers on 2019/05/21

Since many HTTP stacks do not have fields for this so it’s hard to get the originating IP address:

It is about these HTTP header fields with and without X- prefix:

  • Forwarded
  • X-Forwarded-For
  • X-Forwarded-By
  • X-Forwarded-Proto

Note that widely used tools like HAProxy do not always fully adhere to the “standard”…

Via:

–jeroen

Posted in Communications Development, Development, HTTP, Internet protocol suite, Software Development, TCP | Leave a Comment »

Delphi XE8 introduced the dependency directive, but it’s not for Windows

Posted by jpluimers on 2019/05/21

Interesting thread that shows Delphi XE8 introduced a dependency directive: [WayBack] Just curious, in which version was the dependency directive introduced? As in procedure X; external ‘somelib’ dependecy ‘otherlib’; S… – Johan Bontes – Google+

It’s documented as of XE8: [WayBack] Procedures and Functions (Delphi) – RAD Studio: Specifying Dependencies of the Library

The earliest use I could find is in XE4 source C:\Program Files (x86)\Embarcadero\RAD Studio\11.0\source\IBX\IBIntf.pas

–jeroen

Posted in Delphi, Development, Software Development | Leave a Comment »

The Initialization-Block of a unit that is part of a package. Is it run as part of DLLMain?

Posted by jpluimers on 2019/05/16

The interesting question a while back [WayBack] The Initialization-Block of a unit that is part of a package. Is it run as part of DLLMain? – Alexander Benikowski – Google+ has a simple TL;DR answer: “it depends” on the actual usage of those units.

Way more elaborate, as I dislike language stuff that you need to track down by trial and error what is actually used:

Alexander Benikowski
Well, seems so(in our case). Rootcall which triggers the initialization is:
ntdll.ldrLoadDLL
I did not mention, that the BPL is used by a DLL(DLL links against package) which means the package is loaded/initialized by the Os when the DLLMain runs. Odd combination but that seems to be the culprit here.

David Heffernan
Yes, it is triggered from DllMain. And yes, this has massive consequences for what can and cannot be done in initialization sections.

Alexander Benikowski
+David Heffernan in my case. When a packages unit is already initialized by being used from an Exe(which links to the Package), it is not from within a DLLMain.
In my case, both the Application and the dll it loads, both link to the same package. But the unit in question is unused until the DLL is loaded.

Uwe Raabe
The docs for InitializePackage say it calls the initialization parts of all contained units in the package – not only the used ones.

David Heffernan
+Alexander Benikowski​ In that scenario we have load time linking and I guess the package framework handles it differently.

David Millington
Related: don’t forget that class constructors and destructors effectively run in the initialization and finalization sections too. Restrictions or side effects apply there too. docwiki.embarcadero.com – Methods (Delphi) – RAD Studio

Stefan Glienke
+Uwe Raabe Which is not being done when you use it as runtime package. Only initialization sections from unit being used are being run. This caused us several problems in the past where 2 modules (A being the host application exe and B being some DLL that gets loaded at a later point via LoadLibrary) were using a runtime package but only B used a particular unit from the package which caused the initialization code for that unit being executed when B was loaded and hence being executed in the context of the dllmain of B.

The usual solution is then to put those units into some dummy unit forcing the initialization of that unit to be run in A.

Another solution according to your statement could be to call InitializePackage on all the used runtime packages – and there the question is: couldn’t the RTL do that somehow?

Uwe Raabe
+Stefan Glienke I am not sure if that is desirable when done unconditionally. Even when compiled with packages I wouldn’t expect units to be initialized which aren’t actually used. That would perhaps change the behavior of the application depending on whether it is compile with runtime packages or without.
The case is different with dynamic loaded packages. The units in there are obviously not directly used in the first place. As no one can know which units of such a package are used or not, initializing all of them seems like a viable decision.
Of course there will be situations where your proposed behavior might come in handy, but I doubt that this will be a fit for all.

Source: The Initialization-Block of a unit that is part of a package. Is it run as pa…

Related:

–jeroen

Posted in Delphi, Development, Software Development | Leave a Comment »

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