31 lines
586 B
C
31 lines
586 B
C
typedef uint32_t u32;
|
|
|
|
// have to a multiply of 2
|
|
#define COMMA 8 @\label{comma}@
|
|
#define COMMA_FIX (COMMA >> 1)
|
|
|
|
void heron_sqrt(u32 *mem) {
|
|
int i = mem[0];
|
|
while (i > 0) {
|
|
u32 s = mem[i];
|
|
u32 x = s;
|
|
if (s > 1) {
|
|
// x_0 = (s + 1) / 2
|
|
// without increment to avoid overflow for 0xffffffff
|
|
x = x >> 1;
|
|
u32 old_x = x;
|
|
|
|
while(1) {
|
|
// x_{n + 1} = (x_n + (s / x_n)) / 2
|
|
x = (x >> 1) + ((s/x) >> 1);
|
|
if (old_x <= x) {
|
|
break;
|
|
}
|
|
old_x = x;
|
|
}
|
|
}
|
|
mem[i] = x << COMMA_FIX;
|
|
i--;
|
|
}
|
|
}
|