This is a pretty deep rabbit hole, and I don’t know if I’ve explored all of its twists and turns yet. But here’s a first draft of an answer; suggestions for improvement are welcome. At its core, the culprit is the so-called “fused multiply-add” (or, in this case, a fused multiply-subtract). Fused multiply-add is a … Read more
It is surprising that gcc doesn’t support this natively as the code is clearly available in the source within a directory called soft-fp. It’s possible to compile that library manually: $ svn co svn://gcc.gnu.org/svn/gcc/trunk/libgcc/ libgcc $ cd libgcc/soft-fp/ $ gcc -c -O2 -msoft-float -m32 -I../config/arm/ -I.. *.c $ ar -crv libsoft-fp.a *.o There are a … Read more
public class Test { public static void main (String[] args) { String myString = “BF800000”; Long i = Long.parseLong(myString, 16); Float f = Float.intBitsToFloat(i.intValue()); System.out.println(f); System.out.println(Integer.toHexString(Float.floatToIntBits(f))); } }
Some investigation in assembly code. (OllyDbg) #include <stdio.h> #include <math.h> int main(void) { int x1 = (int) pow(10, 2); int x2 = (int) pow(10, 2); printf(“%d %d”, x1, x2); return 0; } The related assembly section: FLD QWORD PTR DS:[402000] // Loads 2.0 onto stack SUB ESP,8 FSTP QWORD PTR SS:[ESP] FLD QWORD PTR DS:[402008] … Read more
To add to Vladimir F’s answer I’ll mention that gfortran 5.0 (but not earlier) supports the IEEE intrinsic modules. Instead of real x x=0 x=0/x one can use use, intrinsic :: iso_fortran_env use, intrinsic :: ieee_arithmetic integer(int32) i real(real32) x x = ieee_value(x, ieee_quiet_nan) i = transfer(x,i) This gives you a little flexibility over which … Read more
The cvtsd2ss instruction uses the FPU’s rounding mode to do the conversion. The default rounding mode is round-to-nearest-even. In order to follow the algorithm, it helps to keep in mind the information at the IEEE 754-1985 Wikipedia page, especially the diagrams representing the layout. First, the exponent of the target float is computed: the double … Read more
The number 0.298475 isn’t representable exactly in a double (since it’s not a fraction whose denominator is a power of two, being 11939/40000), and the actual number that is stored is actually closer to 0.29847 than to 0.29848.
Try this Console.WriteLine(dummy.ToString(“F”)); You can also specify number of decimal places. For example F5, F3, etc. Also, you can check custom format specifier Console.WriteLine(dummy.ToString(“0.#########”));
Here are five (really four-and-a-half) possible solutions. Solution 1: use Python 3.9 or later Python 3.9, released in October 2020, includes a new standard library function math.nextafter which provides this functionality directly: use math.nextafter(x, math.inf) to get the next floating-point number towards positive infinity. For example: >>> from math import nextafter, inf >>> nextafter(100.0, inf) … Read more
It is to accomodate systems (mainly embedded) where floating point math is not possible or necessary. It’s kind of historical indeed but don’t forget that gcc and most other C compilers were written in a time where a 386SX was considered a high performance processor. To give an example, when I still worked in embedded … Read more