Simple question but difficult to me. I want to generate uniformly distributed random numbers between 0 and 1, how can I do it? In matlab I am using rand, in C++ rand() returns integers.
- 1possible duplicate of C++ random float number generationShafik Yaghmour– Shafik Yaghmour2014-03-08 02:22:50 +00:00Commented Mar 8, 2014 at 2:22
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3 Answers
Since C++11, use std::uniform_real_distribution
Comments
maybe you can use the RAND_MAX constant to divide the randomly generated integer
7 Comments
AStupidNoob
Remember to cast it to a double/float!
rand() / (float)RAND_MAX
miushock
ah very fast catch :) saved my answer from being useless
pjs
It's common to need numbers that are in the range
[0,1) rather than [0,1], in which case divide by (RAND_MAX+1.0).pjs
@pio note that I said
+1.0, not +1.pjs
@pio The conversion to float is necessary anyway to get uniforms between 0 and 1, so that seems like a reasonable place to kick accomplish it in C++.
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It really depends on how random you need the numbers to be. Generally, if I don't care about how random it is I will just use rand and divide by MAX_RAND (I bet matlab's rand is better than c's rand).
However, most of what I have done has required a better random number generator than the c function rand, and I don't need it to be cryptographically secure. In this case I use a mersenne twister class (http://www.bedaux.net/mtrand/) which has seemed to work better for the simulated annealing and monte carlo simulations that I sometimes find myself doing.
Also with this class, there is a way to get a random int32 and a radom double (between 0 and 1) out.
