math.h

Our professor said that you can't calculate a b if a<0 using pow() because pow() uses natural logarithms to calculate it (a b =e b ln a ) and since it's undefined for negative numbers it can't be calculated. I tried it and it works as long as b is an integer. I have searched through math.h and further files, but was unable to find how the function is defined and what it uses to calculate. I also tried searching the internet, but without any success. There are similar questions on Stack Overflow right here and here (for C#). (the last one is good, but I was unable to find sourcecode.) So the

Strange things happen when i try to find the cube root of a number. The following code returns me undefined. In cmd : -1.#IND cout<<pow(( double )(20.0*(-3.2) + 30.0),( double )1/3) While this one works perfectly fine. In cmd : 4.93242414866094 cout<<pow(( double )(20.0*4.5 + 30.0),( double )1/3) From mathematical way it must work since we can have the cube root from a negative number. Pow is from Visual C++ 2010 math.h library. Any ideas? pow(x, y) from <cmath> does NOT work if x is negative and y is non-integral. This is a limitation of std::pow , as documented in the C standard and on

I have a sample file here: #include <stdio.h> #include <math.h> int main(){ printf("%f\n", log(10)); } When I compile it with gcc sample.c -o a it works just fine. I can run it with ./a and it produces the output 2.302585 like expected. Yet, when my file looks like this: #include <stdio.h> #include <math.h> int main(){ double a = 10; printf("%f\n", log(a)); } it does not compile with gcc sample.c -o a . Instead, I have to use gcc sample.c -o a -lm so that I can apparently tell it to "link math"...That's where I don't really follow, why wouldn't I have to link math in the first example? And

I have a bunch of these errors and am at a dead end. Found plenty of answers on google but unfortunately none of them work I am using Visual Studio 2012. All the files it says is cant find are on my computer in this folder C:\Program Files\Microsoft Visual Studio 11.0\VC\include Even when I right click on the include statement and click on 'Open Document ' it takes me to the document, so it is clearly there and can be seen I tried adding the directory to the 'Additional Directories' field in options too but did not solve it. If I use the include statement with the full path like so : #include

I am looking for SIMD math libraries (preferably open source) for SSE and AVX. I mean for example if I have a AVX register v with 8 float values I want sin(v) to return the sin of all eight values at once. AMD has a propreitery library, LibM http://developer.amd.com/tools/cpu-development/libm/ which has some SIMD math functions but LibM only uses AVX if it detects FMA4 which Intel CPUs don't have. Also I'm not sure it fully uses AVX as all the function names end in s4 (d2) and not s8 (d4). It give better performance than the standard math libraries on Intel CPUs but it's not much better. Intel

Do the C and C++ standards require the math operations in math.h on floating points (i.e. sqrt , exp , log , sin , ...) to return numerically best solution? For a given (exact and valid) input there can obviously in general not be an exact floating point output from these functions. But is the output required to be the representable value nearest to the mathematically exact one? If not, are there any requirements on precision whatsoever (possibly platform-specific / in other standards ?), so that I am able to make worst-case estimates of calculation errors in my code? What are typical limits