#pragma GCC target ("avx2") #pragma GCC optimization ("O3") #pragma GCC optimization ("unroll-loops")

#pragma GCC target ("avx2")

This pragma instructs the compiler to generate code specifically optimized for the AVX2 (Advanced Vector Extensions 2) instruction set. AVX2 is an extension of the x86 instruction set architecture that provides support for vectorized operations, allowing the processor to perform multiple operations in parallel.

#pragma GCC optimization ("O3")

This pragma sets the compiler optimization level to O3, which enables aggressive optimization. The O3 optimization level is the highest level of optimization provided by GCC and includes various optimizations such as loop unrolling, inlining, and instruction scheduling to produce faster and more efficient code.

#pragma GCC optimization ("unroll-loops")

This pragma specifically instructs the compiler to perform loop unrolling optimization. Loop unrolling involves replicating the body of a loop to reduce loop control overhead and potentially improve instruction pipelining and overall performance. Unrolling loops can lead to better utilization of hardware resources and increased speed.