c - Runtime of Initializing an Array Zero-Filled -

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if define following array using zero-fill initialization syntax on stack:

int arr[ 10 ] = { 0 };

... run time constant or linear?

my assumption it's linear run time -- assumption targeting fact calloc must go on every byte zero-fill it.

if provide why , not it's order xxx tremendous!

the runtime linear in array size.

to see why, here's sample implementation of memset, initializes array arbitrary value. @ assembly-language level, no different goes on in code.

void *memset(void *dst, int val, size_t count) {     unsigned char *start = dst;     (size_t = 0; < count; i++)         *start++ = value;     return dst; }

of course, compilers use intrinsics set multiple array elements @ time. depending on size of array , things alignment , padding, might make runtime on array length more staircase, step size based on vector length. on small differences in array size, make runtime constant, general pattern still linear.


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