ieee-754 | 易学教程

Flush to Zero when a computation results in a denormal number in linux

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A computation in my C code is producing a gradual underflow, and when it happens the program is terminating with SIGFPE. How can I flush the result to zero when a gradual underflow (Denormal) results from a computation, and not terminate the execution? (I am working on a redhat linux machine). Thanks. You haven't specified the architecture - I'm going to take a guess that it's a relatively recent x86[-64], in which case you can manipulate the SSE control register using _mm_getcsr , _mm_setcsr , specified in the <xmmintrin.h> (or <immintrin.h> ) header. The 'flush-to-zero' bit is set with

How are double-precision floating-point numbers converted to single-precision floating-point format?

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问题 Converting numbers from double-precision floating-point format to single-precision floating-point format results in loss of precision. What's the algorithm used to achieve this conversion? Are numbers greater than 3.4028234e+38 or lesser than -3.4028234e+38 simply reduced to the respective limits? I feel that the conversion process is a bit more involved than this but I couldn't find documentation for it. 回答1: The most common floating-point formats are the binary floating-point formats

Flush to Zero when a computation results in a denormal number in linux

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问题 A computation in my C code is producing a gradual underflow, and when it happens the program is terminating with SIGFPE. How can I flush the result to zero when a gradual underflow (Denormal) results from a computation, and not terminate the execution? (I am working on a redhat linux machine). Thanks. 回答1: You haven't specified the architecture - I'm going to take a guess that it's a relatively recent x86[-64], in which case you can manipulate the SSE control register using _mm_getcsr , _mm

Question regarding IEEE 754, 64 bits double?

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问题 Please take a look at the following content: I understand how to convert a double to a binary based on IEEE 754. But I don't understand what the formula is used for. Can anyone give me an example when we use the above formula, please? Thanks a lot. 回答1: The formula that is highlighted in red can be used to calculate the real number that a 64-bit value represents when treated as a IEEE 754 double. It's only useful if you want to manually calculate the conversion from binary to the base-10 real

Is 0 divided by infinity guaranteed to be 0?

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问题 According to this question, n/inf is expected to be zero for n != 0 . What about when n == 0 ? According to IEEE-754, is (0 / inf) == 0 always true? 回答1: Mathematically, 0/0 is indeterminate, and 0/anything_else is zero. IEEE-754 works the same way. So 0/infinity will yield a zero. 0/0 will yield a NaN. Note: not all C++ implementations support IEEE floating point, and some that do so don't completely meet IEEE specifications, so this is not necessarily a C++ question. 来源： https:/

Why doesn't python decimal library return the specified number of signficant figures for some inputs

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问题 NB : this question is about significant figures. It is not a question about "digits after the decimal point" or anything like that. EDIT : This question is not a duplicate of Significant figures in the decimal module. The two questions are asking about entirely different problems. I want to know why the function about does not return the desired value for a specific input. None of the answers to Significant figures in the decimal module address this question. The following function is

Parse HEX float

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问题 I have integer, for example, 4060 . How I can get HEX float ( \x34\xC8\x7D\x45 ) from it? JS hasn't float type, so I don't know how to do this conversion. Thank you. 回答1: The above answer is no longer valid. Buffer has been deprecated (see https://nodejs.org/api/buffer.html#buffer_new_buffer_size). New Solution: function numToFloat32Hex(v,le) { if(isNaN(v)) return false; var buf = new ArrayBuffer(4); var dv = new DataView(buf); dv.setFloat32(0, v, true); return ("0000000"+dv.getUint32(0,!(le|

Double - IEEE 754 alternatives

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问题 According to the following site: http://en.cppreference.com/w/cpp/language/types "double - double precision floating point type. Usually IEEE-754 64 bit floating point type". It says "usually". What other possible formats/standard could C++ double use? What compiler uses an alternative to the IEEE format? Or architecture? 回答1: Vaxen, Crays, and IBM mainframes, to name just a few that are still in reasonably wide use. Most (all?) of those can also do IEEE floating point now, but sometimes only

For any finite floating point value, is it guaranteed that x - x == 0?

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问题 Floating point values are inexact, which is why we should rarely use strict numerical equality in comparisons. For example, in Java this prints false (as seen on ideone.com): System.out.println(.1 + .2 == .3); // false Usually the correct way to compare results of floating point calculations is to see if the absolute difference against some expected value is less than some tolerated epsilon. System.out.println(Math.abs(.1 + .2 - .3) < .00000000000001); // true The question is about whether or

How to get Python division by -0.0 and 0.0 to result in -Inf and Inf, respectively?

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问题 I have a situation where it is reasonable to have a division by 0.0 or by -0.0 where I would expect to see +Inf and -Inf, respectively, as results. It seems that Python enjoys throwing a ZeroDivisionError: float division by zero in either case. Obviously, I figured that I could simply wrap this with a test for 0.0. However, I can't find a way to distinguish between +0.0 and -0.0. (FYI you can easily get a -0.0 by typing it or via common calculations such as -1.0 * 0.0). IEEE handles this all