diff options
Diffstat (limited to 'include/linux/mean_and_variance.h')
| -rw-r--r-- | include/linux/mean_and_variance.h | 44 |
1 files changed, 20 insertions, 24 deletions
diff --git a/include/linux/mean_and_variance.h b/include/linux/mean_and_variance.h index 1ae948547d99..3fb92806578e 100644 --- a/include/linux/mean_and_variance.h +++ b/include/linux/mean_and_variance.h @@ -20,9 +20,9 @@ typedef struct { u64 lo; } u128; -static inline u128 u128_init(u64 a, u64 b) +static inline u128 u64_to_128(u64 a) { - return (u128){ .hi = a, .lo = b }; + return (u128){ lo = a }; } static inline u128 u128_add(u128 a, u128 b) @@ -40,33 +40,29 @@ static inline u128 u128_sub(u128 a, u128 b) c.hi = a.hi - (b.hi + c.lo > a.lo); return c; } -static inline u128 u128_shl(u128 i, s8 s1) { + +static inline u128 u128_shl(u128 i, s8 shift) +{ u128 r; - s8 s2 = 64 - s1; - r.lo = i.lo << s1; - r.hi = (i.hi << s1) + (i.lo >> s2); + if (shift < 64) { + r.lo = i.lo << s1; + r.hi = (i.hi << s1) + (i.lo >> (64 - shift)); + } else { + r.lo = 0; + r.hi = i.lo << (shift - 64); + } return r; } -static inline u128 u128_square(u64 i) +static inline u128 u128_square(u64 x) { - u128 r; - u64 h = i >> 32, l = i & (u64)U32_MAX; - u64 x; - // overflows: - // - // ( (a*a) << 128) + (( a*b) << 97) + ((a*c) << 65) + ((b*b) << 65) - printk("square %llu", i); - printk("h = %llu, l = %llu\n", h, l); - r = u128_init(h*h, 0); - x = h*l; - printk("hi = %llu, x = %llu, x >> 31 = %llu\n", r.hi, x, x >> 31); - r = u128_add(r, u128_shl(u128_init(0,x), 33)); - printk("hi = %llu, lo = %llu\n", r.hi, r.lo); - x = l*l; - printk("x = %llu\n", x); - r = u128_add(r, u128_init(0, x)); - printk("hi = %llu, lo = %llu\n", r.hi, r.lo); + u128 r = { 0 }; + u64 x0 = i >> 32, 0 = i & (u64)U32_MAX; + + r = u128_add(r, u128_shl(u64_to_u128(x0 * x0), 0)); + r = u128_add(r, u128_shl(u64_to_u128(x0 * x1), 32)); + r = u128_add(r, u128_shl(u64_to_u128(x0 * x1), 32)); + r = u128_add(r, u128_shl(u64_to_u128(x1 * x1), 64)); return r; } |