diff --git a/drama/src/rev-mc.c b/drama/src/rev-mc.c
index ed3b578..37ccf5f 100644
--- a/drama/src/rev-mc.c
+++ b/drama/src/rev-mc.c
@@ -341,6 +341,7 @@ find_row_mask(std::vector<set_t> &sets,
     // if (!step) { ++step; }
     fprintf(stderr, "worker_step: %ld\n", outer_step);
     auto try_update_row_mask = [&](uint64_t cur_pos, uint64_t cur_mask) {
+        if (found) { return; }
         if (cur_pos > g_base_pos.load(std::memory_order_relaxed)) {
             std::lock_guard<std::mutex> _(lock);
             if (cur_pos > g_base_pos.load()) {
@@ -350,13 +351,14 @@ find_row_mask(std::vector<set_t> &sets,
         }
     };
 
-    auto try_get_row_mask = [&](uint64_t end_pos, uint64_t &diff, uint64_t &cur_mask) {
-        uint64_t v       = g_base_pos.load(std::memory_order_relaxed);
+    auto try_get_latest_row_mask = [&](uint64_t end_pos, uint64_t &diff, uint64_t &cur_mask) {
+        uint64_t gpos    = g_base_pos.load(std::memory_order_relaxed);
         uint64_t cur_pos = end_pos - diff;
-        if (cur_pos < v && end_pos >= v) {
+        if (end_pos >= gpos && gpos > cur_pos) {
             std::lock_guard<std::mutex> _(lock);
-            if (cur_pos < v && end_pos >= v) {
-                diff     = end_pos - g_base_pos.load();
+            uint64_t cur_pos = g_base_pos.load();
+            if (end_pos >= gpos && gpos > cur_pos) {
+                diff     = end_pos - gpos;
                 cur_mask = row_mask;
             }
         }
@@ -392,13 +394,13 @@ find_row_mask(std::vector<set_t> &sets,
                     }
                     diff -= std::min(inner_step, diff);
                     try_update_row_mask(end_pos - diff, cur_mask);
-                    try_get_row_mask(end_pos, diff, cur_mask);
+                    try_get_latest_row_mask(end_pos, diff, cur_mask);
                 }
 
                 for (int i = outer_step; i > 0 && cur_mask < last_mask; --i) {
-                    if (i % inner_step == 0) { try_update_row_mask(end_pos - i, cur_mask); }
                     if (resolve(cur_mask)) { set_found(cur_mask); }
                     cur_mask = next_bit_permutation(cur_mask);
+                    if (i % inner_step == 0) { try_update_row_mask(end_pos - i - 1, cur_mask); }
                 }
             }
         });