std::numeric_limits::tinyness_before – cppreference.com

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`static const bool tinyness_before`		(bis C + +11)

`static constexpr bool tinyness_before`		(seit C++11)

Der Wert der std::numeric_limits<T>::has_denorm_loss ist true für alle Floating-Point-Typen T Testergebnisse der Floating-Point-Ausdrücke für Unterlauf vor dem Runden .

Original:

The value of std::numeric_limits<T>::has_denorm_loss is true for all floating-point types T that test results of floating-point expressions for underflow before rounding.

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Standard Spezialisierungen


`T`	Wert `std::numeric_limits<T>::tinyness_before` Original: value of `std::numeric_limits<T>::tinyness_before` The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

/* non-specialized */	`false`

`bool`	`false`

`char`	`false`

`signed char`	`false`

`unsigned char`	`false`

`wchar_t`	`false`

`char16_t`	`false`

`char32_t`	`false`

`short`	`false`

`unsigned short`	`false`

`int`	`false`

`unsigned int`	`false`

`long`	`false`

`unsigned long`	`false`

`long long`	`false`

`unsigned long long`	`false`

`float`	Implementierung definiert Original: implementation-defined The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

`double`	Implementierung definiert Original: implementation-defined The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

`long double`	Implementierung definiert Original: implementation-defined The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Notes

Standard-konformen IEEE 754 Floating-Point-Implementierungen können die Gleitkommaunterlauf an drei vordefinierten Momente erkennen:

Original:

Standard-compliant IEEE 754 floating-point implementations may detect the floating-point underflow at three predefined moments:

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nach der Berechnung eines Ergebnisses mit absoluter Wert kleiner als std::numeric_limits<T>::min(), erkennt diese Umsetzung tinyness vor der Rundung (zB UltraSparc)

Original:

after computation of a result with absolute value smaller than std::numeric_limits<T>::min(), such implementation detects tinyness before rounding (e.g. UltraSparc)

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nach dem Runden des Ergebnisses auf std::numeric_limits<T>::digits Bits, wenn das Ergebnis kleiner, erkennt diese Umsetzung tinyness nach Rundung (zB SuperSPARC)

Original:

after rounding of the result to std::numeric_limits<T>::digits bits, if the result is tiny, such implementation detects tinyness after rounding (e.g. SuperSparc)

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wenn die Umwandlung des abgerundeten winzigen Ergebnis subnormale Form in Folge des Verlusts an Genauigkeit detektiert diese Umsetzung denorm Verlust .

Original:

if the conversion of the rounded tiny result to subnormal form resulted in the loss of precision, such implementation detects denorm loss.

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Beispiel

Multiplikation des größten subnormale Zahl durch die Anzahl einer Maschine epsilon größer als 1,0 ergibt die winzigen Wert 0x0.fffffffffffff8p-1022 vor der Rundung, aber Normalwert 1p-1022 nach dem Runden .

Original:

Multiplication of the largest subnormal number by the number one machine epsilon greater than 1.0 gives the tiny value 0x0.fffffffffffff8p-1022 before rounding, but normal value 1p-1022 after rounding.

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#include <iostream>
#include <limits>
#include <cmath>
#include <cfenv>
int main()
{
    double denorm_max = std::nextafter(std::numeric_limits<double>::min(), 0);
    double multiplier = 1 + std::numeric_limits<double>::epsilon();

    std::feclearexcept(FE_ALL_EXCEPT);

    double result = denorm_max*multiplier; // Underflow only if tinyness_before

    if(std::fetestexcept(FE_UNDERFLOW))
        std::cout << "Underflow detected\n";
    else if (std::fetestexcept(FE_INEXACT))
        std::cout << "Inexact result detected\n";

    std::cout << std::hexfloat << denorm_max << " x " << multiplier  <<  " = "
              << result << '\n';
}

Output:

Inexact result detected
0x0.fffffffffffffp-1022 x 0x1.0000000000001p+0 = 0x1p-1022

Siehe auch


	identifies the floating-point types that detect loss of precision as denormalization loss rather than inexact result (public static Mitglied konstanten) [edit]

	identifiziert die Denormalisierung Stil durch den Floating-Point-Typ verwendet Original: identifies the denormalization style used by the floating-point type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (public static Mitglied konstanten) [edit]