# Questions tagged [floating-point]

Approximate representation of numbers as a fixed number of digits multiplied by a logarithmic scale.

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### Why floating point representation uses a sign bit instead of 2's complement to indicate negative numbers

Consider a fixed point representation which can be regarded as a degenerate case of a floating number. It is entirely possible to use 2's complement for negative numbers. But why is a sign bit ...
2k views

### Inequality caused by float inaccuracy

At least in Java, if I write this code: float a = 1000.0F; float b = 0.00004F; float c = a + b + b; float d = b + b + a; boolean e = c == d; the value of $e$ ...
403 views

### Floating point rounding

Can an IEEE-754 floating point number < 1 (i.e. generated with a random number generator which generates a number >= 0.0 and < 1.0) ever be multiplied by some integer (in floating point form) to ...
3k views

### Represent a real number without loss of precision

Current floating point (ANSI C float, double) allow to represent an approximation of a real number. Is there any way to represent real numbers without errors? Here's an idea I had, which is anything ...
581 views

### Implementation of Naive Bayes

I am implementing a Naive Bayes algorithm for text categorization with Laplacian smoothing. The problem I am having is that the probability approaches zero because I am multiplying many small ...
239 views

### Why does floating point modulus exactness matters?

Most Smalltalk dialects currently implement a naive inexact floating modulus (fmod/remainder). I just changed this to improve Squeak/Pharo and eventually other Smalltalk adherence to standards (IEEE ...
856 views

### Number of FLOPs (floating point operations) for exponentiation

What is the number of floating point operations needed to perform exponentiation (power of)? Assuming multiplication of two floats use one FLOP, the number of operations for $x^n$ will be $n-1$. ...
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### Difference between ways to compare floating-point numbers

There seems to be many approaches to judge whether two floating-point numbers are identical. Here are some examples I've found: ...
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### What is the reason of inaccuracy of operations on float numbers?

I wonder why in JavaScript 0.1 + 0.2 // return 0.30000000000000004 4%0.1 // return 0.09999999999999978 http://jsbin.com/oHISAfU/1/edit (Example) In C the ...
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### Program transformations for numeric stability

There's tons of research on program transformations for optimization. Is there any research on transformations that improve numeric stability? Examples of such transformations might include: ...
430 views

### Simple algorithm for IEEE-754 division on 8-bit CPU?

IEEE Std 754-2008 is the modern definition of Floating-Point Arithmetic. It requires that division (among other operations) performs as if it first produced an intermediate result correct to ...
2k views

### Confused by Floating Point Spacing

I'm currently taking a numerical analysis class in college and we're covering floating point systems. For the most part, I have a good grasp on it. However, something I can't seem to visualize, and ...
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### What is the state of the algorithmic art for floating point arithmetic on complex numbers?

Most modern compilers and processors implement the IEEE 754 binary formats for floating point numbers. IEEE 754 guarantees that the addition, subtraction, multiplication, division, and square root ...
158 views

### Proof that (x-y)(x+y) is more accurate than x²-y²

I was carrying on my reading of What Every Computer Scientist Should Know About Floating-Point Arithmetic but got stuck on the proof of Theorem 2 (page 34). At some point it says: \begin{align} (x \...
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### Imaginary numbers and negative zero

I've been studying the low-level hardware implementations of floating point numbers and doing an exercise to design a custom floating point implementation. I know that being able to represent ...
60 views

### Union of fixed and floating point types

Say I have two real number types. They may be floating or fixed point. How can I construct a new type whose values are at least the union of the two with the minimal number of bits? There are 3 cases ...
3k views

### What does normalizing with hidden bit really mean?

I have a question related to representing numbers in base 2 with floating point. For example, if I have such a number $$0.000011 \cdot 2^3$$ then is its normalized form this? $$1.1\cdot 2^{-2}$$ ...
223 views

### Can we improve the precision of IEEE floats by dropping leading zeros in the mantissa?

It seems like it would be possible to add more precision to the IEEE 32-bit mantissa system if the leading zeroes were also dropped, just like the leading 1 is dropped due to it being implicitly known....
120 views

### When does the IEEE-754 64-bit float break as a counter

As a matter of curiosity I've been trying to determine at what point a 64-bit float no longer reflects the addition of 1 as expected; that is, at what point the digits as printed do not correspond to ...
777 views

### Is the exponent in floating point numbers signed or unsigned

This may be sound like a stupid question, because, of course, it can be negative and, as Wikipedia states: A numeric variable is signed if it can represent both positive and negative numbers, and ...
231 views

### Is < binary relation a strict partial order on IEEE doubles?

To me it looks that it is: irreflexivity: NaN < NaN == false transitivity: if a < b and b < c then a < c (the antecedent is never true for NaNs) asymmetry: if a < b then not b < a (...
260 views

### Is “flops” a reliable measure of deciding computational capacity?

Is "flops" a reliable measure of deciding computational capacity? If we do matrix multiplication and matrix addition of the same size of matrix, do the flops remain the same? Referring to question ...
100 views

### Floating point format: why must 1−emax ≤ q+p−1 ≤ emax?

From the Wikipedia page on the IEEE Standard for Floating-Point Arithmetic, The possible finite values that can be represented in a format are determined by the base (b), the number of digits in ...
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### How much can we trust mathematical software when working with large numbers, and how much memory it needs to work with these numbers?

For example, I want to evaluate the expression: $3^{3^{{3}^{3}}}$ so I used wolframalpha.com (it's free, and I don't own any software), which returned the scientific notation of the number above, ...
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### Why do I get really different results with my benchmarking code I made?

I'm doing research work for my last year in high school. My work is about processors and for the experimental part i've coded an app that can mesure how many Floating Point Operation can a processor ...
402 views

### Why do floating point values have infinity?

Why do floating point values have infinity instead of just a higher exponent?
235 views

### Why a separate ALU is needed, since any integer can be represented as floating point numbers?

Most of the operations in computer are using floating point arithmetic.Put it simply why a Floating Point Unit alone is not sufficient? Can we do away with ALU?Is FP operations are resource intensive ...
546 views

### Whether assigning of single precision IEEE754 float to double is reversible?

Using the IEEE754 standard, let's assign single precision variable s to double precision variable d and then assign d to single precision variable s'. Is this operation is reversible (lossless) for ...
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### Smallest number close to 0 in IEEE754 (64bits)?

I thought the smallest number close to 0 would be : 0 00000000001 (exponent) 0000000000000000000000000000000000000000000000000000 (significand) But this site (http://binaryconvert.com/result_double....
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### Representing Computations on Transcendental Numbers

Consider the set of transcendental numbers that are not compressible to a finite base-2 representation. How can I compute multiples (more generally, any algebraic computation) of one of these numbers,...
195 views

### What's the algorithm for floating points equality test?

I've found that 0.1 + 0.2 == 0.3 is not true in Java (see this demo). So, I'm interested in how equality testing can be implemented for floats. Is there a ...
3k views

### Floating point normalised numbers in binary

Many text books state that for a binary floating point representation in a computer byte, that if the mantissa is normalised, then a positive number must start with 01 from the left or a negative ...
213 views

### Gap between numbers in fixed-point vs. floating point arithmetic

If $r$ is a machine-representable number and $f(r)$ is the next larger machine representable number, are the following true or false? In fixed-point arithmetic, the distance between $r$ and $f(r)$ is ...
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### Floating point arithmetic

I need to change x1 = 0.3 and x2 = -0.29 to a FP(floating point) number with one sign bit, a 4 bit mantissa, a 3 bit exponent. The results I got are: x1: 0 001 0011 x2: 1 001 0010 I am also trying ...
483 views

### Will floating point code return the same arithmetical results on two different computers?

Say I am using boost or the built-in float or double mathematical libraries of my C++ compiler. I distribute the program. Will the execution of my C++ program on different machines given different ...
755 views

### Floating Point Systems - Rounding Error in Taylor series

I have a question about rounding error. I have created a function to approximate exp(x) by summing the terms of its taylor series until the sum stops changing. (That is, 1 + x + x^2/2! ...). This ...
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### Why multiplying float number by multiple of 10 seems to preserve better precision?

It is famous that for float numbers: .1 + .2 != .3 but 1+2=3 It seems that multiplying floats by 10 allows you to preserve ...
368 views

### Find the duplicates in a list of floating point numbers

I receive a list of real numbers ( float ) between $0$ and $1$. The list has length $N+1$ and I need to find two numbers on the list which are $\le \frac{1}{N}$ ...
128 views

### Approximate a float using a minimal fraction

This sounds like it's probably a well-known problem, but I haven't been able to find references to it by searching. Given a floating point value $x$ and an error range $\varepsilon$, how can I ...
1k views

### Calculating Binet's formula for Fibonacci numbers with arbitrary precision

Binet's formula for the nth Fibonacci numbers is remarkable because the equation "converts" via a few arithmetic operations an irrational number $\phi$ into an integer sequence. However, using finite ...
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### numerically stable log1pexp calculation

What are good approximations for computing log1pexp for single precision and double precision floating point numbers? Note: ...
528 views

### Distribution of IEEE 754 single precision floating point over number line

"What is the maximum and minimum difference between two successive real numbers representable in IEEE 754 Single Precision and Double Precision Floating Point Representations respectively?" In ...
6k views

### Hex Bit Pattern to IEEE 754 standard Floating Point Number

The question asks for the decimal number that 0x0C000000 represents if it is a floating number. I'm not too sure on how to approach this, but here's my thought process: 0x0C000000 = 0000 1100 0000 ...