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Questions tagged [multiprecision]

83 questions
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2 answers

How many 64-bit multiplications are needed to calculate the low 128-bits of a 64-bit by 128-bit product?

Consider that you want to calculate the low 128-bits of the result of multiplying a 64-bit and 128-bit unsigned number, and that the largest multiplication you have available is the C-like 64-bit multiplication which takes two 64-bit unsigned inputs…
BeeOnRope
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6 answers

Storing and printing integer values greater than 2^64

I am trying to write a program for finding Mersenne prime numbers. Using the unsigned long long type I was able to determine the value of the 9th Mersenne prime, which is (2^61)-1. For larger values I would need a data type that could store integer…
user1918672
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2 answers

higher precision floating point using boost lib (higher then 16 digits)

I am running a simulation of physical experiments, so I need really high floating point precision (more than 16 digits). I use Boost.Multiprecision, however I can't get a precision higher than 16 digits, no matter what I tried. I run the simulation…
bnaya
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1 answer

How to use sqrt and ceil with Boost::multiprecision?

Do you know how to do this simple line of code without error using Boost::multiprecison ? boost::multiprecision::cpp_int v, uMax, candidate; //... v += 6 * ceil((sqrt(uMax * uMax - candidate) - v) / 6); Using MSVC there is an error for "sqrt" and…
Aurélien Barbier-Accary
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1 answer

C++: convert "boost::multiprecision::float128" to "double"

I'm using the boost multiprecision library, and more precisely the boost::multiprecision::float128 type. Using ICPC for compiling, I get some errors when trying to to do something like: double a = functionA(); where functionA() return a…
user1403546
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1 answer

Exact decimal division in MySQL

How to properly divide two DECIMAL values in MySQL and get a result accurate to the number of digits defined in the column type? Example: select cast(1/2 as decimal(4,4)), cast(1 as decimal(4,4))/2, cast(1 as decimal(4,4))/cast(2 as…
Ferdinand.kraft
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1 answer

How to convert from boost::multiprecision::cpp_int to cpp_dec_float<0> (rather than to cpp_dec_float_50, etc.)?

As is made clear in the Boost Multiprecision library documentation, it is straightforward to convert from a boost::multiprecision::cpp_int to a boost::multiprecision::cpp_dec_float: // Some interconversions between number types are completely…
Dan Nissenbaum
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4
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3 answers

Is it possible to store 2 32-bit values in one long int variable?

I want to store two 32-bit values in a single long int variable. How would you do this on a 32-bit OS using C? Is it possible to store the data in a single long long variable? If so, how is that done?
Syedsma
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1 answer

Mathematical operations between two strings

I'm trying to add subtract and multiply numbers with huge decimals C++. Example: 4125487821547.87879845215584844588 - 354556689.899455132265468 What I figured so far is that I need to save inputs as a string, but not sure how to proceed after…
Djon
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1 answer

how to change at runtime number precision with boost::multiprecision

I've read from the boost::multiprecision documentation: Depending upon the number type, precision may be arbitrarily large (limited only by available memory), fixed at compile time (for example 50 or 100 decimal digits), or a variable controlled at…
Jepessen
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4
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1 answer

Eigen3 dynamic matrix with boost::multiprecision::mpfr_float

I would like to make matrices and use them using the Eigen3 library, with my number type being Boost.Multiprecision's mpfr_float wrapper. I can make the matrices just fine, but working with them fails for everything I've tried except matrix…
ofloveandhate
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2 answers

Print cpp_dec_float in scientific notation without trailing zeros

I'm using cpp_dec_float for arbitrary precision, and it's great, but I'm having trouble figuring out how to print all significant digits. For example, with this code to setup using boost::multiprecision::cpp_dec_float; typedef…
user1382306
4
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2 answers

Multiword addition in C

I have a C program which uses GCC's __uint128_t which is great, but now my needs have grown beyond it. What are my options for fast arithmetic with 196 or 256 bits? The only operation I need is addition (and I don't need the carry bit, i.e., I will…
Charles
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1 answer

multiprecision unsigned subtraction in C

I am trying to implement multi-precision unsigned subtraction over a finite field (p=2^191-19) in C, but I cannot figure out how to deal with borrow bit! My operands are represented in radix-2^16 as: typedef unsigned long long T[12]; which means…
A23149577
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Multiplication with very large operands

I am implementing a multi-precision module, and at this moment I am stuck in the multiplication. To do my algorithm I need to multiply two unsigned operands of 64 bits, using a Haswell microarchitecture, and store the result in a memory block. I'm…
Hélder Gonçalves
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