What Determines the Default Setting of the x87 FPU Control Word?

Posted by Rick Regan on Stack Overflow See other posts from Stack Overflow or by Rick Regan
Published on 2010-03-31T15:00:32Z Indexed on 2010/03/31 15:03 UTC
Read the original article Hit count: 405

Filed under:

fpu

|

floating-point

|

floating-accuracy

|

rounding

|

visual-c++

What determines the default setting of the x87 FPU control word -- specifically, the precision control field? Does the compiler set it based on the target processor? Is there a compiler option to change it?

Using Microsoft Visual C++ 2008 Express Edition on an Intel Core Duo processor, the default setting for the precision control field is "01b", meaning double (53 bit) precision. I'm wondering -- why is the default not "11"b, or extended (64 bit) precision?

(I know I can change it using _controlfp.)

© Stack Overflow or respective owner

Related posts about fpu

nasm infinite loop with FPU

as seen on Stack Overflow - Search for 'Stack Overflow'
i'm trying to create a small nasm program which do this operation in floating point while(input <= 10^5) do begin input = input * 10 i = i - 1 end the equivilant program in nasm is as following section .data input: resd 1 n10: dd 0x41200000 ; 10 _start: mov eax… >>> More
How to change FPU context in signal handler (C++/Linux)

as seen on Stack Overflow - Search for 'Stack Overflow'
I wrote a signal handler to catch FPE errors. I need to continue execution even if this happens. I receive a ucontext_t as parameter, I can change the bad operand from 0 to another value but the FPU context is still bad and I run into an infinite loop ? Does someone already manupulate the ucontext_t… >>> More
What Determines the Default Setting of the x87 FPU Control Word?

as seen on Stack Overflow - Search for 'Stack Overflow'
What determines the default setting of the x87 FPU control word -- specifically, the precision control field? Does the compiler set it based on the target processor? Is there a compiler option to change it? Using Microsoft Visual C++ 2008 Express Edition on an Intel Core Duo processor, the default… >>> More
Controlling FPU behavior in an OpenMP program?

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a large C++ program that modifies the FPU control word (using _controlfp()). It unmasks some FPU exceptions and installs a SEHTranslator to produce typed C++ exceptions. I am using VC++ 9.0. I would like to use OpenMP (v.2.0) to parallelize some of our computational loops. I've already… >>> More
does android 1.5 saves fpu regs on context switch

as seen on Stack Overflow - Search for 'Stack Overflow'
i'm asking 1.5 and up or is it dependant on what's in ".config" when compiled for my phone? (and yes, i know that android has to support processors with soft-float, but several libm on different phones do have hard-float libm) (please provide -if possible- any link to/file name of context switching… >>> More

Related posts about floating-point

Comparing floating point values

as seen on Stack Overflow - Search for 'Stack Overflow'
I just read a statement about the floating point value comparison Floating point values shall not be compared using either the == or != operators. Most floating point values have no exact binary representation and have a limited precision. If so what is the best method for comparing two floating… >>> More
understanding floating point variables

as seen on Stack Overflow - Search for 'Stack Overflow'
There is some problem, i can't understand anyway. look at this code please <script type="text/javascript"> function math(x) { var y; y = x*10; alert(y); } </script> <input type="button" onclick="math(0.011)"> What must be alerted after i click on button? i think 0.11… >>> More
floating point hex octal binary

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am working on a calculator that allows you to perform calculations past the decimal point in octal, hexadecimal, binary, and of course decimal. I am having trouble though finding a way to convert floating point decimal numbers to floating point hexadecimal, octal, binary and vice versa. The… >>> More
What is a Bias Value of Floating Point Numbers?

as seen on Stack Overflow - Search for 'Stack Overflow'
In learning how floating point numbers are represented in computers I have come across the term "bias value" that I do not quite understand. The bias value in floating point numbers has to do with the negative and positiveness of the exponent part of a floating point number. The bias value of a… >>> More
Why are floating point values so prolific?

as seen on Stack Overflow - Search for 'Stack Overflow'
So, title says it all. Why are floating point values so prolific in computer programming. Due to problems like rounding errors, and not being able to even accurately represent numbers such as 0.1, I really can't see how they got as far as they did. I understand that the computation is faster… >>> More