floating-point-precision

Possible Duplicate: Float to binary in C++ I have a very small double var, and when I print it I get -0. (using C++). Now in order to get better precision I tried using cout.precision(18); \\i think 18 is the max precision i can get. cout.setf(ios::fixed,ios::floatfield); cout<<var;\\var is a double. but it just writes -0.00000000000... I want to see the exact binary representation of the var. In other words I want to see what binary number is written in the stack memory/register for this var. union myUnion { double dValue; uint64_t iValue; }; myUnion myValue; myValue.dValue=123.456; cout <<

Let's say that we have declared the following variables float a = 1.2291; float b = 3.99; float variables have precision 6, which (if I understand correctly) means that the difference between the number that the computer actually stores and the actual number that you want will be less than 10^-6 that means that both a and b have some error that is less than 10^-6 so inside the computer a could actually be 1.229100000012123 and b could be 3.9900000191919 now let's say that you have the following code float c = 0; for(int i = 0; i < 1000; i++) c += a + b; my question is, will c 's final result

Is it the case that: Representable floating point values are densest in the real number line near zero? Representable floating point values grow sparser (exponentially?) as the number line moves away from zero? If the above two are true, does that mean there is less precision farther from zero? Overall question: Does precision in some way refer to or depend on the density of numbers you can represent (accurately)? The term precision usually refers to the number of significant digits (bits) in the represented value. So precision varies with the number of bits (or digits) in the mantissa of

I have the following repetitive simple code repeated several times that I would like to make a function for: for i in range(10): id = "some id string looked up in dict" val = 63.4568900932840928 # some floating point number in dict corresponding to "id" tabStr += '%-15s = %6.1f\n' % (id,val) I want to be able to call this function: def printStr(precision) Where it preforms the code above and returns tabStr with val to precision decimal points. For example: printStr(3) would return 63.457 for val in tabStr . Any ideas how to accomplish this kind of functionality? tabStr += '%-15s = %6.*f\n' %

I'm creating a numpy array of random values and adding them to an existing array containing 32-bit floats. I'd like to generate the random values using the same dtype as the target array, so that I don't have to convert the dtypes manually. Currently I do this: import numpy as np x = np.zeros((10, 10), dtype='f') x += np.random.randn(*x.shape).astype('f') What I'd like to do instead of the last line is something like: x += np.random.randn(*x.shape, dtype=x.dtype) but randn (and actually none of the numpy.random methods) does not accept a dtype argument. My specific question is, is it possible