1 /* Copyright (c) 2011-2013. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
7 #include "mc_private.h"
11 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_liveness, mc,
12 "Logging specific to algorithms for liveness properties verification");
14 /********* Global variables *********/
16 xbt_dynar_t acceptance_pairs;
17 xbt_dynar_t visited_pairs;
18 xbt_dynar_t successors;
21 /********* Static functions *********/
23 static xbt_dynar_t get_atomic_propositions_values(){
26 unsigned int cursor = 0;
27 xbt_automaton_propositional_symbol_t ps = NULL;
28 xbt_dynar_t values = xbt_dynar_new(sizeof(int), NULL);
30 xbt_dynar_foreach(_mc_property_automaton->propositional_symbols, cursor, ps){
31 f = (int_f_void_t)ps->function;
33 xbt_dynar_push_as(values, int, res);
39 static int get_search_interval(xbt_dynar_t all_pairs, mc_pair_t pair, int *min, int *max){
41 int raw_mem_set = (mmalloc_get_current_heap() == raw_heap);
45 int cursor = 0, previous_cursor, next_cursor;
48 int end = xbt_dynar_length(all_pairs) - 1;
51 cursor = (start + end) / 2;
52 pair_test = (mc_pair_t)xbt_dynar_get_as(all_pairs, cursor, mc_pair_t);
53 if(pair_test->nb_processes < pair->nb_processes){
55 }else if(pair_test->nb_processes > pair->nb_processes){
58 if(pair_test->heap_bytes_used < pair->heap_bytes_used){
60 }else if(pair_test->heap_bytes_used > pair->heap_bytes_used){
64 previous_cursor = cursor - 1;
65 while(previous_cursor >= 0){
66 pair_test = (mc_pair_t)xbt_dynar_get_as(all_pairs, previous_cursor, mc_pair_t);
67 if(pair_test->nb_processes != pair->nb_processes || pair_test->heap_bytes_used != pair->heap_bytes_used)
69 *min = previous_cursor;
72 next_cursor = cursor + 1;
73 while(next_cursor < xbt_dynar_length(all_pairs)){
74 pair_test = (mc_pair_t)xbt_dynar_get_as(all_pairs, next_cursor, mc_pair_t);
75 if(pair_test->nb_processes != pair->nb_processes || pair_test->heap_bytes_used != pair->heap_bytes_used)
93 static int is_reached_acceptance_pair(mc_pair_t pair){
95 int raw_mem_set = (mmalloc_get_current_heap() == raw_heap);
99 if(xbt_dynar_is_empty(acceptance_pairs)){
101 if(pair->graph_state->system_state == NULL){
102 pair->graph_state->system_state = MC_take_snapshot();
103 pair->heap_bytes_used = mmalloc_get_bytes_used(std_heap);
105 xbt_dynar_push(acceptance_pairs, &pair);
114 if(pair->graph_state->system_state == NULL){
115 pair->graph_state->system_state = MC_take_snapshot();
116 pair->heap_bytes_used = mmalloc_get_bytes_used(std_heap);
119 int min = -1, max = -1, index;
123 index = get_search_interval(acceptance_pairs, pair, &min, &max);
125 if(min != -1 && max != -1){ /* Acceptance pair with same number of processes and same heap bytes used exists */
126 res = xbt_parmap_mc_apply(parmap, snapshot_compare, xbt_dynar_get_ptr(acceptance_pairs, min), (max-min)+1, pair);
130 return ((mc_pair_t)xbt_dynar_get_as(acceptance_pairs, (min+res)-1, mc_pair_t))->num;
132 xbt_dynar_insert_at(acceptance_pairs, min, &pair);
134 pair_test = (mc_pair_t)xbt_dynar_get_as(acceptance_pairs, index, mc_pair_t);
135 if(pair_test->nb_processes < pair->nb_processes){
136 xbt_dynar_insert_at(acceptance_pairs, index+1, &pair);
138 if(pair_test->heap_bytes_used < pair->heap_bytes_used)
139 xbt_dynar_insert_at(acceptance_pairs, index + 1, &pair);
141 xbt_dynar_insert_at(acceptance_pairs, index, &pair);
155 static void set_acceptance_pair_reached(mc_pair_t pair){
157 int raw_mem_set = (mmalloc_get_current_heap() == raw_heap);
161 if(xbt_dynar_is_empty(acceptance_pairs)){
163 if(pair->graph_state->system_state == NULL){
164 pair->graph_state->system_state = MC_take_snapshot();
165 pair->heap_bytes_used = mmalloc_get_bytes_used(std_heap);
167 xbt_dynar_push(acceptance_pairs, &pair);
171 if(pair->graph_state->system_state == NULL){
172 pair->graph_state->system_state = MC_take_snapshot();
173 pair->heap_bytes_used = mmalloc_get_bytes_used(std_heap);
176 size_t current_bytes_used = pair->heap_bytes_used;
177 int current_nb_processes = pair->nb_processes;
181 int end = xbt_dynar_length(acceptance_pairs) - 1;
183 mc_pair_t pair_test = NULL;
184 size_t bytes_used_test = 0;
185 int nb_processes_test;
188 cursor = (start + end) / 2;
189 pair_test = (mc_pair_t)xbt_dynar_get_as(acceptance_pairs, cursor, mc_pair_t);
190 bytes_used_test = pair_test->heap_bytes_used;
191 nb_processes_test = pair_test->nb_processes;
192 if(nb_processes_test < current_nb_processes)
194 if(nb_processes_test > current_nb_processes)
196 if(nb_processes_test == current_nb_processes){
197 if(bytes_used_test < current_bytes_used)
199 if(bytes_used_test > current_bytes_used)
201 if(bytes_used_test == current_bytes_used)
206 if(pair_test->nb_processes < pair->nb_processes){
207 xbt_dynar_insert_at(acceptance_pairs, cursor+1, &pair);
209 if(pair_test->heap_bytes_used < pair->heap_bytes_used)
210 xbt_dynar_insert_at(acceptance_pairs, cursor + 1, &pair);
212 xbt_dynar_insert_at(acceptance_pairs, cursor, &pair);
222 static void remove_acceptance_pair(mc_pair_t pair){
224 int raw_mem_set = (mmalloc_get_current_heap() == raw_heap);
228 unsigned int cursor = 0;
232 xbt_dynar_foreach(acceptance_pairs, cursor, pair_test){
233 if(pair_test->num == pair->num){
240 xbt_dynar_remove_at(acceptance_pairs, cursor, NULL);
242 pair->acceptance_removed = 1;
244 if(pair->stack_removed && pair->acceptance_removed){
245 if(_sg_mc_visited == 0){
246 MC_pair_delete(pair);
247 }else if(pair->visited_removed){
248 MC_pair_delete(pair);
256 static int is_visited_pair(mc_pair_t pair){
258 if(_sg_mc_visited == 0)
261 int raw_mem_set = (mmalloc_get_current_heap() == raw_heap);
265 if(xbt_dynar_is_empty(visited_pairs)){
267 if(pair->graph_state->system_state == NULL)
268 pair->graph_state->system_state = MC_take_snapshot();
269 xbt_dynar_push(visited_pairs, &pair);
278 if(pair->graph_state->system_state == NULL)
279 pair->graph_state->system_state = MC_take_snapshot();
281 int min = -1, max = -1, index;
285 index = get_search_interval(visited_pairs, pair, &min, &max);
287 if(min != -1 && max != -1){ /* Visited pair with same number of processes and same heap bytes used exists */
288 res = xbt_parmap_mc_apply(parmap, snapshot_compare, xbt_dynar_get_ptr(visited_pairs, min), (max-min)+1, pair);
290 pair_test = (mc_pair_t)xbt_dynar_get_as(visited_pairs, (min+res)-1, mc_pair_t);
291 if(pair_test->other_num == -1)
292 pair->other_num = pair_test->num;
294 pair->other_num = pair_test->other_num;
295 if(dot_output == NULL)
296 XBT_DEBUG("Pair %d already visited ! (equal to pair %d)", pair->num, pair_test->num);
298 XBT_DEBUG("Pair %d already visited ! (equal to pair %d (pair %d in dot_output))", pair->num, pair_test->num, pair->other_num);
299 xbt_dynar_remove_at(visited_pairs, (min + res) - 1, NULL);
300 xbt_dynar_insert_at(visited_pairs, (min+res) - 1, &pair);
301 pair_test->visited_removed = 1;
302 if(pair_test->stack_removed && pair_test->visited_removed){
303 if((pair_test->automaton_state->type == 1) || (pair_test->automaton_state->type == 2)){
304 if(pair_test->acceptance_removed){
305 MC_pair_delete(pair_test);
308 MC_pair_delete(pair_test);
313 return pair->other_num;
315 xbt_dynar_insert_at(visited_pairs, min, &pair);
317 pair_test = (mc_pair_t)xbt_dynar_get_as(visited_pairs, index, mc_pair_t);
318 if(pair_test->nb_processes < pair->nb_processes){
319 xbt_dynar_insert_at(visited_pairs, index+1, &pair);
321 if(pair_test->heap_bytes_used < pair->heap_bytes_used)
322 xbt_dynar_insert_at(visited_pairs, index + 1, &pair);
324 xbt_dynar_insert_at(visited_pairs, index, &pair);
328 if(xbt_dynar_length(visited_pairs) > _sg_mc_visited){
329 int min2 = mc_stats->expanded_pairs;
330 unsigned int cursor2 = 0;
331 unsigned int index2 = 0;
332 xbt_dynar_foreach(visited_pairs, cursor2, pair_test){
333 if(pair_test->num < min2){
335 min2 = pair_test->num;
338 xbt_dynar_remove_at(visited_pairs, index2, &pair_test);
339 pair_test->visited_removed = 1;
340 if(pair_test->stack_removed && pair_test->acceptance_removed && pair_test->visited_removed)
341 MC_pair_delete(pair_test);
353 static int MC_automaton_evaluate_label(xbt_automaton_exp_label_t l, xbt_dynar_t atomic_propositions_values){
357 int left_res = MC_automaton_evaluate_label(l->u.or_and.left_exp, atomic_propositions_values);
358 int right_res = MC_automaton_evaluate_label(l->u.or_and.right_exp, atomic_propositions_values);
359 return (left_res || right_res);
362 int left_res = MC_automaton_evaluate_label(l->u.or_and.left_exp, atomic_propositions_values);
363 int right_res = MC_automaton_evaluate_label(l->u.or_and.right_exp, atomic_propositions_values);
364 return (left_res && right_res);
367 int res = MC_automaton_evaluate_label(l->u.exp_not, atomic_propositions_values);
371 unsigned int cursor = 0;
372 xbt_automaton_propositional_symbol_t p = NULL;
373 xbt_dynar_foreach(_mc_property_automaton->propositional_symbols, cursor, p){
374 if(strcmp(p->pred, l->u.predicat) == 0)
375 return (int)xbt_dynar_get_as(atomic_propositions_values, cursor, int);
388 /********* DDFS Algorithm *********/
391 void MC_ddfs_init(void){
393 initial_state_liveness->raw_mem_set = (mmalloc_get_current_heap() == raw_heap);
395 XBT_DEBUG("**************************************************");
396 XBT_DEBUG("Double-DFS init");
397 XBT_DEBUG("**************************************************");
399 mc_pair_t initial_pair = NULL;
400 smx_process_t process;
402 MC_wait_for_requests();
406 acceptance_pairs = xbt_dynar_new(sizeof(mc_pair_t), NULL);
407 visited_pairs = xbt_dynar_new(sizeof(mc_pair_t), NULL);
408 successors = xbt_dynar_new(sizeof(mc_pair_t), NULL);
410 initial_state_liveness->snapshot = MC_take_snapshot();
411 initial_state_liveness->prev_pair = 0;
415 unsigned int cursor = 0;
416 xbt_automaton_state_t automaton_state;
418 xbt_dynar_foreach(_mc_property_automaton->states, cursor, automaton_state){
419 if(automaton_state->type == -1){ /* Initial automaton state */
423 initial_pair = MC_pair_new();
424 initial_pair->automaton_state = automaton_state;
425 initial_pair->graph_state = MC_state_new();
426 initial_pair->atomic_propositions = get_atomic_propositions_values();
428 /* Get enabled process and insert it in the interleave set of the graph_state */
429 xbt_swag_foreach(process, simix_global->process_list){
430 if(MC_process_is_enabled(process)){
431 MC_state_interleave_process(initial_pair->graph_state, process);
435 initial_pair->requests = MC_state_interleave_size(initial_pair->graph_state);
436 initial_pair->search_cycle = 0;
438 xbt_fifo_unshift(mc_stack_liveness, initial_pair);
445 MC_restore_snapshot(initial_state_liveness->snapshot);
450 }else if(automaton_state->type == 2){ /* Acceptance automaton state */
454 initial_pair = MC_pair_new();
455 initial_pair->automaton_state = automaton_state;
456 initial_pair->graph_state = MC_state_new();
457 initial_pair->atomic_propositions = get_atomic_propositions_values();
459 /* Get enabled process and insert it in the interleave set of the graph_state */
460 xbt_swag_foreach(process, simix_global->process_list){
461 if(MC_process_is_enabled(process)){
462 MC_state_interleave_process(initial_pair->graph_state, process);
466 initial_pair->requests = MC_state_interleave_size(initial_pair->graph_state);
467 initial_pair->search_cycle = 1;
469 xbt_fifo_unshift(mc_stack_liveness, initial_pair);
473 set_acceptance_pair_reached(initial_pair);
478 MC_restore_snapshot(initial_state_liveness->snapshot);
484 if(initial_state_liveness->raw_mem_set)
495 smx_process_t process;
496 mc_pair_t current_pair = NULL;
498 if(xbt_fifo_size(mc_stack_liveness) == 0)
501 /* Get current pair */
502 current_pair = (mc_pair_t)xbt_fifo_get_item_content(xbt_fifo_get_first_item(mc_stack_liveness));
504 /* Update current state in buchi automaton */
505 _mc_property_automaton->current_state = current_pair->automaton_state;
507 XBT_DEBUG("********************* ( Depth = %d, search_cycle = %d, interleave size %d)", xbt_fifo_size(mc_stack_liveness), current_pair->search_cycle, MC_state_interleave_size(current_pair->graph_state));
509 mc_stats->visited_pairs++;
512 smx_simcall_t req = NULL;
515 xbt_automaton_transition_t transition_succ;
516 unsigned int cursor = 0;
518 int reached_num, visited_num;
520 mc_pair_t next_pair = NULL;
521 xbt_dynar_t prop_values = NULL;
523 if(xbt_fifo_size(mc_stack_liveness) < _sg_mc_max_depth){
525 if(current_pair->requests > 0){
527 if(current_pair->search_cycle){
529 if((current_pair->automaton_state->type == 1) || (current_pair->automaton_state->type == 2)){
531 if((reached_num = is_reached_acceptance_pair(current_pair)) != -1){
533 XBT_INFO("Pair %d already reached (equal to pair %d) !", current_pair->num, reached_num);
536 xbt_fifo_shift(mc_stack_liveness);
537 if(dot_output != NULL)
538 fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", initial_state_liveness->prev_pair, reached_num, initial_state_liveness->prev_req);
541 XBT_INFO("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
542 XBT_INFO("| ACCEPTANCE CYCLE |");
543 XBT_INFO("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
544 XBT_INFO("Counter-example that violates formula :");
545 MC_show_stack_liveness(mc_stack_liveness);
546 MC_dump_stack_liveness(mc_stack_liveness);
547 MC_print_statistics(mc_stats);
554 if((visited_num = is_visited_pair(current_pair)) != -1){
557 if(dot_output != NULL)
558 fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", initial_state_liveness->prev_pair, visited_num, initial_state_liveness->prev_req);
564 while((req = MC_state_get_request(current_pair->graph_state, &value)) != NULL){
567 if(dot_output != NULL){
568 if(initial_state_liveness->prev_pair != 0 && initial_state_liveness->prev_pair != current_pair->num){
569 fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", initial_state_liveness->prev_pair, current_pair->num, initial_state_liveness->prev_req);
570 xbt_free(initial_state_liveness->prev_req);
572 initial_state_liveness->prev_pair = current_pair->num;
576 /* Debug information */
577 if(XBT_LOG_ISENABLED(mc_liveness, xbt_log_priority_debug)){
578 req_str = MC_request_to_string(req, value);
579 XBT_DEBUG("Execute: %s", req_str);
584 if(dot_output != NULL){
585 initial_state_liveness->prev_req = MC_request_get_dot_output(req, value);
586 if(current_pair->search_cycle)
587 fprintf(dot_output, "%d [shape=doublecircle];\n", current_pair->num);
591 MC_state_set_executed_request(current_pair->graph_state, req, value);
592 mc_stats->executed_transitions++;
594 /* Answer the request */
595 SIMIX_simcall_pre(req, value);
597 /* Wait for requests (schedules processes) */
598 MC_wait_for_requests();
601 prop_values = get_atomic_propositions_values();
604 /* Evaluate enabled transition according to atomic propositions values */
606 xbt_dynar_foreach(current_pair->automaton_state->out, cursor, transition_succ){
608 res = MC_automaton_evaluate_label(transition_succ->label, prop_values);
610 if(res == 1){ // enabled transition in automaton
614 next_pair = MC_pair_new();
615 next_pair->graph_state = MC_state_new();
616 next_pair->automaton_state = transition_succ->dst;
617 next_pair->atomic_propositions = get_atomic_propositions_values();
619 /* Get enabled process and insert it in the interleave set of the next graph_state */
620 xbt_swag_foreach(process, simix_global->process_list){
621 if(MC_process_is_enabled(process)){
622 MC_state_interleave_process(next_pair->graph_state, process);
626 next_pair->requests = MC_state_interleave_size(next_pair->graph_state);
628 if(next_pair->automaton_state->type == 1 || next_pair->automaton_state->type == 2 || current_pair->search_cycle)
629 next_pair->search_cycle = 1;
631 xbt_fifo_unshift(mc_stack_liveness, next_pair);
633 if(mc_stats->expanded_pairs%1000000 == 0)
634 XBT_INFO("Expanded pairs : %lu", mc_stats->expanded_pairs);
644 /* Then, evaluate true transitions (always true, whatever atomic propositions values) */
646 xbt_dynar_foreach(current_pair->automaton_state->out, cursor, transition_succ){
648 res = MC_automaton_evaluate_label(transition_succ->label, prop_values);
650 if(res == 2){ // true transition in automaton
654 next_pair = MC_pair_new();
655 next_pair->graph_state = MC_state_new();
656 next_pair->automaton_state = transition_succ->dst;
657 next_pair->atomic_propositions = get_atomic_propositions_values();
659 /* Get enabled process and insert it in the interleave set of the next graph_state */
660 xbt_swag_foreach(process, simix_global->process_list){
661 if(MC_process_is_enabled(process)){
662 MC_state_interleave_process(next_pair->graph_state, process);
666 next_pair->requests = MC_state_interleave_size(next_pair->graph_state);
668 if(next_pair->automaton_state->type == 1 || next_pair->automaton_state->type == 2 || current_pair->search_cycle)
669 next_pair->search_cycle = 1;
671 xbt_fifo_unshift(mc_stack_liveness, next_pair);
673 if(mc_stats->expanded_pairs%1000000 == 0)
674 XBT_INFO("Expanded pairs : %lu", mc_stats->expanded_pairs);
684 if(MC_state_interleave_size(current_pair->graph_state) > 0){
685 XBT_DEBUG("Backtracking to depth %d", xbt_fifo_size(mc_stack_liveness));
686 MC_replay_liveness(mc_stack_liveness, 0);
695 mc_stats->executed_transitions++;
697 XBT_DEBUG("No request to execute in this state, search evolution in Büchi Automaton.");
699 if(current_pair->search_cycle){
701 if((current_pair->automaton_state->type == 1) || (current_pair->automaton_state->type == 2)){
703 if((reached_num = is_reached_acceptance_pair(current_pair)) != -1){
705 XBT_INFO("Pair %d already reached (equal to pair %d) !", current_pair->num, reached_num);
708 xbt_fifo_shift(mc_stack_liveness);
711 XBT_INFO("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
712 XBT_INFO("| ACCEPTANCE CYCLE |");
713 XBT_INFO("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
714 XBT_INFO("Counter-example that violates formula :");
715 MC_show_stack_liveness(mc_stack_liveness);
716 MC_dump_stack_liveness(mc_stack_liveness);
717 MC_print_statistics(mc_stats);
724 if((visited_num = is_visited_pair(current_pair)) != -1){
726 XBT_DEBUG("Pair %d already visited ! (equal to pair %d)", current_pair->num, visited_num);
731 prop_values = get_atomic_propositions_values();
734 /* Evaluate enabled transition according to atomic propositions values */
736 xbt_dynar_foreach(current_pair->automaton_state->out, cursor, transition_succ){
738 res = MC_automaton_evaluate_label(transition_succ->label, prop_values);
740 if(res == 1){ // enabled transition in automaton
744 next_pair = MC_pair_new();
745 next_pair->graph_state = MC_state_new();
746 next_pair->automaton_state = transition_succ->dst;
747 next_pair->atomic_propositions = get_atomic_propositions_values();
748 next_pair->requests = MC_state_interleave_size(next_pair->graph_state);
750 if(next_pair->automaton_state->type == 1 || next_pair->automaton_state->type == 2 || current_pair->search_cycle)
751 next_pair->search_cycle = 1;
753 xbt_fifo_unshift(mc_stack_liveness, next_pair);
755 if(mc_stats->expanded_pairs%1000 == 0)
756 XBT_INFO("Expanded pairs : %lu", mc_stats->expanded_pairs);
758 if(dot_output != NULL)
759 fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", current_pair->num, next_pair->num, "");
769 /* Then, evaluate true transitions (always true, whatever atomic propositions values) */
771 xbt_dynar_foreach(current_pair->automaton_state->out, cursor, transition_succ){
773 res = MC_automaton_evaluate_label(transition_succ->label, prop_values);
775 if(res == 2){ // true transition in automaton
779 next_pair = MC_pair_new();
780 next_pair->graph_state = MC_state_new();
781 next_pair->automaton_state = transition_succ->dst;
782 next_pair->atomic_propositions = get_atomic_propositions_values();
783 next_pair->requests = MC_state_interleave_size(next_pair->graph_state);
785 if(next_pair->automaton_state->type == 1 || next_pair->automaton_state->type == 2 || current_pair->search_cycle)
786 next_pair->search_cycle = 1;
788 xbt_fifo_unshift(mc_stack_liveness, next_pair);
790 if(mc_stats->expanded_pairs%1000 == 0)
791 XBT_INFO("Expanded pairs : %lu", mc_stats->expanded_pairs);
793 if(dot_output != NULL)
794 fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", current_pair->num, next_pair->num, "");
808 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
809 if(MC_state_interleave_size(current_pair->graph_state) > 0){
810 XBT_WARN("/!\\ But, there are still processes to interleave. Model-checker will not be able to ensure the soundness of the verification from now. /!\\ ");
811 if(_sg_mc_max_depth == 1000)
812 XBT_WARN("Notice : the default value of max depth is 1000 but you can change it with cfg=model-check/max_depth:value.");
817 if(xbt_fifo_size(mc_stack_liveness) == _sg_mc_max_depth ){
818 XBT_DEBUG("Pair %d (depth = %d) shifted in stack, maximum depth reached", current_pair->num, xbt_fifo_size(mc_stack_liveness) );
820 XBT_DEBUG("Pair %d (depth = %d) shifted in stack", current_pair->num, xbt_fifo_size(mc_stack_liveness) );
825 xbt_dynar_free(&prop_values);
826 current_pair = xbt_fifo_shift(mc_stack_liveness);
827 current_pair->stack_removed = 1;
828 if(current_pair->search_cycle){
829 remove_acceptance_pair(current_pair);
831 if(_sg_mc_visited == 0)
832 MC_pair_delete(current_pair);
833 else if(current_pair->visited_removed)
834 MC_pair_delete(current_pair);