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February 21, 2025 09:45
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Fast Inverse Square Root for Zig
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| const std = @import("std"); | |
| /// Compute the fast inverse square root of a given f32 number. | |
| pub fn fastInvSqrt(number: f32) f32 { | |
| // Interpret the floating-point number as an unsigned 32-bit integer. | |
| var i: u32 = @bitCast(u32, number); | |
| // Magic constant and bit manipulation. | |
| i = 0x5f3759df - (i >> 1); | |
| // Reinterpret the bits back into a floating-point value. | |
| var y: f32 = @bitCast(f32, i); | |
| // One iteration of Newton's method to improve the approximation. | |
| y = y * (1.5 - (number * 0.5 * y * y)); | |
| return y; | |
| } | |
| pub fn main() !void { | |
| var stdout = std.io.getStdOut().writer(); | |
| const number: f32 = 4.0; | |
| const invSqrt = fastInvSqrt(number); | |
| try stdout.print("Fast Inverse Square Root of {} is {}\n", .{number, invSqrt}); | |
| } |
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