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yaml predicated-prefix-sum
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const std = @import("std"); | |
export fn columnCountsVec(chunk: @Vector(16, u8)) @TypeOf(chunk) { | |
var mask = chunk != @as(@TypeOf(chunk), @splat('\n')); | |
var array_count = @select(u8, mask, @as(@TypeOf(chunk), @splat(1)), @as(@TypeOf(chunk), @splat(0))); | |
inline for (0..std.math.log2(@sizeOf(@TypeOf(chunk)))) |i| { | |
array_count = @select(u8, mask, array_count +% std.simd.shiftElementsRight(array_count, 1 << i, 0), array_count); | |
mask = @select(bool, mask, std.simd.shiftElementsRight(mask, 1 << i, false), @as(@TypeOf(mask), @splat(false))); | |
} | |
return std.simd.shiftElementsRight(array_count, 1, 0); | |
} | |
export fn columnCounts(chunk: @Vector(16, u8)) @Vector(16, u8) { | |
const newlines: u16 = @bitCast(@as(@Vector(16, u8), chunk) == @as(@Vector(16, u8), @splat('\n'))); | |
const ones = 0x1111111111111111; | |
const ascending_indices = 0xFEDCBA9876543210; | |
const restart_nibbles_mask = pdep(newlines, ones ^ 1) *% 0xF; | |
const restart_nibbles_indices = pext(ascending_indices, restart_nibbles_mask); | |
const prefix_diff = restart_nibbles_indices -% (restart_nibbles_indices << 4); | |
const vec: @Vector(8, u8) = @bitCast(ascending_indices -% pdep(prefix_diff, restart_nibbles_mask) *% ones); | |
return std.simd.interlace(.{ vec, vec >> @splat(4) }) & @as(@Vector(16, u8), @splat(0xF)); | |
} | |
//pub fn main() void { | |
// const chunk = [16]u8{ 'a', 'b', 'c', '\n', 'e', 'f', '\n', 'h', 'i', '\n', 'k', 'l', 'm', 'n', 'o', 'p' }; | |
// std.debug.print("{}\n", .{columnCountsVec(chunk)}); | |
// | |
// const result = columnCounts(chunk); | |
// std.debug.print("{}\n", .{result}); | |
//} | |
inline fn pdep(src: u64, mask: u64) u64 { | |
return asm ("pdep %[mask], %[src], %[ret]" | |
: [ret] "=r" (-> u64), | |
: [src] "r" (src), | |
[mask] "r" (mask), | |
); | |
} | |
inline fn pext(src: u64, mask: u64) u64 { | |
return asm ("pext %[mask], %[src], %[ret]" | |
: [ret] "=r" (-> u64), | |
: [src] "r" (src), | |
[mask] "r" (mask), | |
); | |
} |
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