Preventing the threads from writing into memory in the inner loop yields the expected speedup

Especially bad is writing into memory where another thread is writing
into the same cache line.

online.cpp

@@ -314,13 +314,16 @@ static value_t parallel_streameval_rdpf(MPCIO &mpcio, const RDPF &dpf,
             [&mpcio, &dpf, &scaled_xor, thread_num, threadstart, threadsize] {
                 MPCTIO tio(mpcio, thread_num);
 //printf("Thread %d from %X for %X\n", thread_num, threadstart, threadsize);
-                auto ev = StreamEval(dpf, threadstart, 0, tio.aes_ops());
+                RegXS local_xor;
+                size_t local_aes_ops = 0;
+                auto ev = StreamEval(dpf, threadstart, 0, local_aes_ops);
                 for (address_t x=0;x<threadsize;++x) {
 //if (x%0x10000 == 0) printf("%d", thread_num);
                     DPFnode leaf = ev.next();
-                    RegXS sx = dpf.scaled_xs(leaf);
-                    scaled_xor[thread_num] ^= sx;
+                    local_xor ^= dpf.scaled_xs(leaf);
                 }
+                scaled_xor[thread_num] = local_xor;
+                tio.aes_ops() += local_aes_ops;
 //printf("Thread %d complete\n", thread_num);
             });
         threadstart = (threadstart + threadsize) % totsize;