On Friday, August 31, 2012 18:33:36 Jelle Hermsen wrote: > Personally I just define pi with 4*atan(1). Is there a good reason to use > M_PI1 instead?
I defined M_PIl as (4*atan(1.)) and ran the program. It gave the same result as defining M_PIl as M_PI. The reason for using M_PIl is that it's a ten-byte float, so multiplying by it will result in better accuracy than multiplying by M_PI, which is an eight-byte float. I once wrote a Mandelbrot/Julia program that gave wrong results; it was continuing the iteration instead of stopping when it saw a previously seen value. I submitted a bug to the GCC authors. It turned out to be not a bug in the compiler. The program was comparing a just-computed point, expressed as a ten-byte float in the processor, with a previously computed point, expressed as an eight-byte float in a double variable, and they were not equal. Pierre -- The Black Garden on the Mountain is not on the Black Mountain.
