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Performance costs of casting number

Z01 · 2002-02-07T16:38:43

Hi I''m writing some code for traversing a quad-tree that needs to be fast performance-wise. I''m trying to choose basic types for my variables right now, and I''m curious if there is any performance cost with casting or its just a compile time thing. (I need to learn some assembly language soon so I can answer these questions for myself ) Specifically, I''m interested in: // I''m mostly interested in these two float newFloat = (float)anInt; float newFloat = (float)anUnsignedChar; // but I would like to know about this one also if possible int newInt = (int)aFloat; I think floating point adds take the same time as adding ints on P3 and higher, but I''m not sure exactly what the speed of these opcodes is. Maybe someone knows? Is casting a variable to a float actually reorganizing the memory contents of that memory address, or is it just the program is looking at the memory contents in a different way? As an example of what I''m thinking about: // stride should be an int because I use for array indexing const int stride = 10; float xUpperLeft = 20.0f; float xUpperRight = xUpperLeft + (float)stride; // ***************** VERSUS // but this might be faster because its a float and there''s no cast const float stride = 10.0f; float xUpperLeft = 20.0f; float xUpperRight = xUpperLeft + stride; Thanks Guys

General and Gameplay Programming Programming

Started by Z01 February 05, 2002 02:41 PM

9 comments, last by Z01 22 years, 2 months ago

Beer Hunter

712

February 07, 2002 04:38 PM

Those of us who have the book would already know about it.
Those of us who don''t have the book have learned nothing just from reading your post.

Just tell us: what method is suggested by Game Programming Gems 2?

Performance costs of casting number

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Performance costs of casting number

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