The Wiert Corner – irregular stream of stuff

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

  • My badges

  • Twitter Updates

  • My Flickr Stream

  • Pages

  • All categories

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 2,917 other followers

Archive for January 12th, 2022

A few tools on my list for research: fswatch, entr, ack and ag

Posted by jpluimers on 2022/01/12

Based on the below tweet and replies, these tools are not on my research list:

[Archive.is] Aaron Patterson on Twitter: “Here is my “autotest for lazy people”. It watches for changes in the lib or test directory, and runs rake test on change. There are definitely better, purpose built tools for this. But I am lazy‚Ķ”

–jeroen

Posted in *nix, *nix-tools, Development, fgrep, find, grep, Power User, Scripting, Software Development | Leave a Comment »

On my research list: “ESXi” “Secure Boot” – Google Search

Posted by jpluimers on 2022/01/12

On my research list:¬†[Wayback] “ESXi” “Secure Boot” – Google Search.

Some links about it:

–jeroen

Posted in ESXi6, ESXi6.5, ESXi6.7, ESXi7, Power User, Virtualization, VMware, VMware ESXi | Leave a Comment »

Covid-19/Coronavirus – Mondneusmaskers en andere PBE: Instructie beschermingsmiddelen en zelftests mantelzorgers en pgb | Publicatie | Rijksoverheid.nl

Posted by jpluimers on 2022/01/12

[Wayback/Archive Instructie beschermingsmiddelen en zelftests mantelzorgers en pgb | Publicatie | Rijksoverheid.nl

Instructie beschermingsmiddelen en zelftests mantelzorgers en pgb

Mantelzorgers en pgb-gefinancierde zorgverleners kunnen bij hun werk gebruikmaken van persoonlijke beschermingsmiddelen of mondneuskapjes. Cli√ęnten kunnen onder voorwaarden gebruik maken van gratis zelftests. In deze instructie staat wanneer zorgverleners persoonlijke beschermingsmiddelen kunnen aanvragen. En wanneer cli√ęnten zelftests kunnen aanvragen.

Download ‘Instructie beschermingsmiddelen en zelftests mantelzorgers en pgb (staand, A3)’1/2

[Wayback] PDF document | 1 pagina | 95 kB

Publicatie | 08-10-2021

Download ‘Instructie beschermingsmiddelen en zelftests mantelzorgers en pgb (liggend, A4)’2/2

[Wayback] PDF document | 2 pagina’s | 130 kB

Publicatie | 08-10-2021

Via:

–jeroen

Posted in LifeHacker, Power User | Leave a Comment »

Het moment om Schiphol te laten krimpen is nu – Follow the Money – Platform voor onderzoeksjournalistiek

Posted by jpluimers on 2022/01/12

[Wayback/Archive] Het moment om Schiphol te laten krimpen is nu – Follow the Money – Platform voor onderzoeksjournalistiek

Via [Archive] Eric Smit on Twitter: “In Europa zijn boekwerken volgeschreven over de vraag hoe je een groeiende capaciteit tussen luchtvaartmaatschappijen verdeelt, maar is er nooit nagedacht over de consequenties van een afnemende capaciteit … via @ftm_nl” / Twitter

jeroen

Posted in Uncategorized | Leave a Comment »

Delphi SetRoundMode: gets sets part of the 8087 control word (related: GetRoundMode and TFPURoundingMode)

Posted by jpluimers on 2022/01/12

I thought I had written about this a long time ago, as Math.SetRoundMode (and now System.Math.SetRoundMode) has been introduced since at least Delphi 2007. There are also related GetRoundMode and TFPURoundingMode.

Delphi 2009 also introduced TFPUPrecisionMode, GetPrecisionMode and SetPrecisionMode.

Delphi 2010 also introduced TFPUException, TFPUExceptionMask, TFPUPrecisionMode, TFPURoundingMode, ClearExceptions, GetExceptionMask, and SetExceptionMask.

Delphi XE2 introduced namespaces, so prepended the unit Math with the namespace System. to become unit System.Math. It also introduced $EXCESSPRECISION (for x64), GetMXCSR, SetMXCSR, ResetMXCSR, ClearFPUExceptions, TSSEException, TSSEExceptionMask, GetSSEExceptionMask, SetSSEExceptionMask, ClearSSEExceptions, TSSERoundingMode, GetSSERoundMode, SetSSERoundMode.

The documentation basically only had formatting changes. This is the most important part of SetRoundMode:

function SetRoundMode(const RoundMode: TFPURoundingMode): TFPURoundingMode;

Call SetRoundingMode to specify how the FPU handles rounding issues. The rounding mode can be any of the following values:

Value
Meaning
rmNearest
Rounds to the closest value.
rmDown
Rounds toward negative infinity.
rmUp
Rounds toward positive infinity.
rmTruncate
Truncates the value, rounding positive numbers down and negative numbers up.

This is the most important bit of SetPrecisionMode:

function SetPrecisionMode(const Precision: TFPUPrecisionMode): TFPUPrecisionMode;

Call SetPrecisionMode to specify the level of precision that the FPU (floating-point unit) uses for floating-point calculations. The precision control mode can be any of the following values:

Value
Meaning
pmSingle
single precision
pmReserved
not used
pmDouble
double precision
pmExtended
extended precision

SetPrecisionMode returns the previous precision control mode.

Both are functions, so so they return the previous value which you can use to set it back later: this is important as it is a process wide. SetPrecisionMode documents this, but SetRoundMode does not!

Global side effects and avoiding them

Since SetRoundMode and SetPrecisionMode set the 8087 CW (and on XE2 and up SetMXCSR), it means all usual Set8087CW caveats apply: changing the global 8087 CW setting impacts all running code, which means that threads, DLLs (especially ones written in other languages), etc might malfunction. You can find some of the caveat effects on my bog by searching for [Wayback] Set8087CW site:wiert.me РGoogle Search.

If you want to avoid global side effects, you might try the solution in [Wayback] c# – What is the equivalent of Math.Round() with MidpointRounding.AwayFromZero in Delphi? – Stack Overflow by [Wayback] Andreas Rejbrand.

On MXCSR

[Wayback/Archive.is] SSE Instruction Set (not sure why Embarcadero used this as reference material from their docwiki, but hey, Intel documentation is likely outdated):

SSE ‚ÄĒ MXCSR

The MXCSR register is a 32-bit register containing flags for control and status information regarding SSE instructions. As of SSE3, only bits 0-15 have been defined.

Pnemonic Bit Location Description
FZ bit 15 Flush To Zero
R+ bit 14 Round Positive
R- bit 13 Round Negative
RZ bits 13 and 14 Round To Zero
RN bits 13 and 14 are 0 Round To Nearest
PM bit 12 Precision Mask
UM bit 11 Underflow Mask
OM bit 10 Overflow Mask
ZM bit 9 Divide By Zero Mask
DM bit 8 Denormal Mask
IM bit 7 Invalid Operation Mask
DAZ bit 6 Denormals Are Zero
PE bit 5 Precision Flag
UE bit 4 Underflow Flag
OE bit 3 Overflow Flag
ZE bit 2 Divide By Zero Flag
DE bit 1 Denormal Flag
IE bit 0 Invalid Operation Flag

FZ mode causes all underflowing operations to simply go to zero. This saves some processing time, but loses precision.

The R+, R-, RN, and RZ rounding modes determine how the lowest bit is generated. Normally, RN is used.

PM, UM, MM, ZM, DM, and IM are masks that tell the processor to ignore the exceptions that happen, if they do. This keeps the program from having to deal with problems, but might cause invalid results.

DAZ¬†tells the¬†CPU¬†to force all Denormals to zero. A Denormal is a number that is so small that¬†FPU¬†can’t renormalize it due to limited exponent ranges. They’re just like normal numbers, but they take considerably longer to process. Note that not all processors support¬†DAZ.

PE,¬†UE,¬†ME,¬†ZE,¬†DE, and¬†IE¬†are the exception flags that are set if they happen, and aren’t unmasked. Programs can check these to see if something interesting happened. These bits are “sticky”, which means that once they’re set, they stay set forever until the program clears them. This means that the indicated exception could have happened several operations ago, but nobody bothered to clear it.

DAZ¬†wasn’t available in the first version of SSE. Since setting a reserved bit in¬†MXCSR¬†causes a general protection fault, we need to be able to check the availability of this feature without causing problems. To do this, one needs to set up a 512-byte area of memory to save the SSE state to, using¬†fxsave, and then one needs to inspect bytes 28 through 31 for the¬†MXCSR_MASK¬†value. If bit 6 is set,¬†DAZ¬†is supported, otherwise, it isn’t.

Architectures Software Developer’s Manual: Intel¬ģ 64 and IA-32 includes supporting processors programming environment and architecture.

[Wayback] Intel¬ģ 64 and IA-32 Architectures Developer’s Manual: Vol. 1

[Wayback]

https://web.archive.org/web/20130603170547/http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-vol-1-manual.pdf

Documentation links

Some of the documentation links (that regrettably do not explain what happens behind the scenes with the 8087 CW) are these:

 

–jeroen

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

 
%d bloggers like this: