Am Thu, 30 May 2013 17:47:14 +0530 schrieb Shriramana Sharma <samj...@gmail.com>:
> Hello. I like that D exposes to me the real type to maximally utilize > the machine's numerical precision. Since I am writing a program > (currently in C++ but I am thinking of moving to D) that has to handle > lots of fractional numbers (calculating offset curves and such) I am > wondering whether/when I should real instead of double or even any > arguments in favour of staying with double (compatibility with > C/C++?). Any pointers appreciated please? I checked the FAQ but it > doesn't seem to mention this. > > Thanks! If you have large amounts of values and want to work on them fast use floats for storage since currently computers have more processing power than memory bandwidth. If you return numbers from functions use real. This allows the compiler to return them as-is from the FPU, whereas double and float require an additional rounding step. The same may apply to temporary variables. Where the amount of numbers is smaller and they fit into CPU cache, the memory bandwidth doesn't matter. 32-bit CPUs work the fastest with floats, whereas 64-bit CPUs work efficiently with doubles. My tip is to use real everywhere in calculations until it comes to storing the results for later use where doubles are more compact. -- Marco
