52-bit: multiprocessing is BLOCKED; single-core DP rho (batch 512) ~>60s
At 52 bits (n=3.36e15) BSGS needs too much memory. Sandbox blocks import multiprocessing (SANDBOX_BLOCKED), so no parallelism. The run tool also has a 60 s limit; DP-rho with 512 walkers, 64-entry additive walk table, Montgomery batch inversion (pow(x,-1,p)), DP mask 2^(bits/2-12), no negation map did not finish the 52-bit practice in 60s (expected ~100-150s single core: ~7e7 steps). Verified correctness on a small 20-bit curve (k recovered). Handle y-sign at DP matches: same y -> (u-u2)=(v2-v)k; opposite y -> (u+u2)=-(v+v2)k. Next idea: add negation map (sqrt2) with cycle-escape, or reduce per-step Python overhead.