The comment says between min and max (min < x < max), but the function will return (min <= x <= max)
I'm just trying to clarify the actual intent of this function. Was the author intending the former, or latter? Chris ----- Original Message ----- From: "Alberto Luaces" <[EMAIL PROTECTED]> To: "OpenSceneGraph Users" <[email protected]> Sent: Thursday, January 31, 2008 10:09 AM Subject: Re: [osg-users] get_random > El Thursday 31 January 2008 16:41:55 DC Fennell escribió: >> Hello everybody, >> >> I believe the get_random() function in range under osgParticle should be: >> minimum + (maximum - minimum) * rand() / (RAND_MAX + 1); >> It is written as: >> >> minimum + (maximum - minimum) * rand() / RAND_MAX; >> >> If you expect the values returned (as specified in the comments) to be >> between min and max (min < x < max), then this function could give >> incorrect results, since there are instances where rand() returns >> RAND_MAX. >> >> Is the intent of this function, in mathematical terms, to return (min, >> max) >> or (min, max] ? >> >> This question applies to get_random_sqrtf() as well. >> >> Thanks. >> >> Chris. > > I think it is taken directly from a known recomendation from the > book "Numerical Recipes in C: The Art of Scientific Computing". It is > mentioned in the man page of the rand() function: > > "If you want to generate a random integer between 1 and 10, you should > always > do it by using high-order bits, as in > > > j = 1 + (int) (10.0 * (rand() / (RAND_MAX + 1.0))); > > > and never by anything resembling > > > j = 1 + (rand() % 10); > > > (which uses lower-order bits)." > > I think it was more important for the original writer to get high quality > random numbers than to match the exact range. Maybe the documentation > should > be changed in order to say that it returns min < x <= max, or the > function, > decrementing the max arg passed one unit, so the value returned could be > min > < x <= max-1 which would mean min < x < max when dealing with integers. > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
