Questions related to `long double` floating-point data-type (numbers) as commonly found in languages like C and C++. Sometimes referred to as quadruple-precision floating-point data-type (numbers).
Questions tagged [long-double]
143 questions
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votes
1 answer
Compiling Windows C++ application with long doubles in VS2010
At work we have MSVS2010 Ultimate, and I'm writing a program which runs exhaustive simulations using real numbers. I'm getting non-trivial round-off errors and I've already taken reasonable steps to ensure my algorithm is as numerically stable as…
Ozzah
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votes
1 answer
Favorite/Best A.X=B Solver that Supports Long Doubles?
I am hoping to repeatedly hammer an X=B(A^-1) problem. That is, solve a linear system. For C++, which numerical solvers have support for 128bit long doubles (quads)?
Using C style arrays is a major plus as all my 2D data is stored as a single…
Mikhail
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1 answer
Crazy behaviour during execution
I have been doing some inline-asm with gcc. Everything is ALMOST working, up to some behaviour that is just baffling me. I am evaluating a rational polynomial, but need to use 80-bit constants. The generated code seems to be perfect, but on…
David I. McIntosh
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Microsoft's edX C++ course: double vs long double - why a lack of common standard?
I'm in a Software Development A.S. degree program at a local community college. I want to get ahead of my college program (which I find too simplistic). So, I'm studying different languages and technologies everywhere I can (online).
I decided to go…
InfiniteLoop
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4 answers
How to convert a NSString to long double?
I am dealing with a long double value that can have huge values.
At one time I have this number represented as NSString and I need to convert it to long double. I see that the only API I have is
[myString doubleValue];
I don't see a…
Duck
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votes
2 answers
How to force long double in Perl
I lose precision when doing arithmetic or trying to print (debug) numbers this big:
1234567890.123456789
I think my problems are with $d (result of arithmetic) and the formatted print of $e.
How can I force long doubles? My Perl version (5.8.4 on…
dnvrdave
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4 answers
Cout long double issue
So, I'm working on a C++ project. I have a var of long double type and assigned it a value like "1.02"
Then, I try to use cout to print it and the result is: -0
I already tried to use setprecision and all I found googling the problem.
What is the…
nervousDev
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1 answer
Difference between double and long double in c++
Can someone explain the differences between doubles and long doubles except for the difference in precision to me? I wrote a program to solve a gravitational n-body problem so i basically integrate second order differential equations and my program…
user3642133
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confusion with data structure allignment?
Code 1:-
struct emp
{
char a;
double b;
};
int main()
{
struct emp e;
printf("%p %p", (void*)&e.a, (void*)&e.b);
}
Output on my computer:-
OO28FF00 0028FF08
As the size of char and double is '1' and '8' respectively and hence the…
kevin gomes
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accessing long double bit representation
TLDR; Does the following code invoke undefined (or unspecified) behaviour ?
#include
#include
void printme(void *c, size_t n)
{
/* print n bytes in binary */
}
int main() {
long double value1 = 0;
long double value2 =…
andreabedini
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votes
2 answers
Sum of two "np.longdouble"s yields big numerical error
Good morning,
I'm reading two numbers from a FITS file (representing the integer and floating point parts of a single number), converting them to long doubles (128 bit in my machine), and then summing them up.
The result is not as precise as I would…
matteo
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votes
2 answers
Is long double useful in ANSI C?
There is a data type in C89 (ANSI C) standard called long double, but there is no any mathematical function to support long double (). For example, sin function accepts a long argument.
C99 supports mathematical functions for long double.
My…
Amir Saniyan
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votes
1 answer
Long double precision error saturation in RK integrator
I'm trying to write an integrator which uses long doubles for very high precision. I know that my system architecture has long double support, but for some reason, the precision of my integrator maxes out at 16 significant digits. Here's some code…
David
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Format specifier %Lf is giving errors for `long double` variables
I am getting the following errors:
In function 'main':
[Warning] unknown conversion type character 'L' in format [-Wformat=]
[Warning] too many arguments for format [-Wformat-extra-args]
In function 'error_user':
[Warning] unknown conversion type…
Henry
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votes
1 answer
Support for float128 (np.longdouble) in scipy.stats
I would like to make some probability computations with scipy.stats, and avoid under/overflows:
in addition to using the appropriate log-functions, I tried to increase the float precision using numpy.longdouble (float128 on Ubuntu).
However, the…
PlasmaBinturong
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