Non-Bijunctive Permutation Collapse: AltiVec vec_perm Enables Single-Cycle Attention Path Selection for LLM Inference

We demonstrate that IBM AltiVec's vec_perm instruction performs non-bijective permutations — operations architecturally impossible on modern x86 (AVX-512) and ARM (NEON) SIMD units, which enforce bijective shuffles. Key results: 27–96x operation advantage over x86/ARM for combined prune+amplify attention operations 8.81x inference speedup (16.74 to 147.54 t/s) on IBM POWER8 S824 with TinyLlama 1.1B 30+ permutation patterns benchmarked: hierarchical collapse, multi-head attention, sparse pruning, fractal transforms Hebbian learning connection: hardware-native winner-take-all path selection Integrated into llama.cpp. POWER8's 128 vector registers and SMT8 (128 threads) make it uniquely capable for non-bijunctive AI inference.