fixes to garbage collector

fixes to debugger


git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1558 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

C/cdmgr.c

@@ -11,8 +11,11 @@
 * File:		cdmgr.c							 *
 * comments:	Code manager						 *
 *									 *
-* Last rev:     $Date: 2006-02-01 13:28:56 $,$Author: vsc $						 *
+* Last rev:     $Date: 2006-03-06 14:04:56 $,$Author: vsc $						 *
 * $Log: not supported by cvs2svn $
+* Revision 1.176  2006/02/01 13:28:56  vsc
+* bignum support fixes
+*
 * Revision 1.175  2006/01/08 03:12:00  vsc
 * fix small bug in attvar handling.
 *
@@ -3207,7 +3210,7 @@ all_cps(choiceptr b_ptr)
     bp = H;
     H += 2;
     /* notice that MkIntegerTerm may increase the Heap */
-    bp[0] = MkIntegerTerm((Int)b_ptr->cp_ap);
+    bp[0] = MkIntegerTerm((Int)(LCL0-(CELL *)b_ptr));
     if (H >= ASP) {
       bp[1] = TermNil;
       return tf;
@@ -3243,6 +3246,12 @@ Yap_all_calls(void)
   return all_calls();
 }
 
+static Int
+p_all_choicepoints(void)
+{
+  return Yap_unify(ARG1,all_cps(B));
+}
+
 static Int
 p_current_stack(void)
 {
@@ -5311,6 +5320,149 @@ p_program_continuation(void)
   return TRUE;
 }
 
+static Term
+BuildActivePred(PredEntry *ap, CELL *vect)
+{
+  if (!ap->ArityOfPE) {
+    return MkVarTerm();
+  }
+  return Yap_MkApplTerm(ap->FunctorOfPred, ap->ArityOfPE, vect);
+}
+
+static Int
+p_choicepoint_info(void)
+{
+  choiceptr cptr = (choiceptr)(LCL0-IntegerOfTerm(Deref(ARG1)));
+  PredEntry *pe;
+  int go_on = TRUE;
+  yamop *ipc = cptr->cp_ap;
+  Term t, tname, tmod;
+  UInt arity;
+
+  while (go_on) {
+    op_numbers opnum = Yap_op_from_opcode(ipc->opc);
+
+    go_on = FALSE;
+    switch (opnum) {
+#ifdef TABLING
+    case _table_load_answer:
+      pe = LOAD_CP(cptr)->cp_pred_entry;
+      t = MkVarTerm();
+      break;
+    case _table_try_answer:
+    case _table_retry_me:
+    case _table_trust_me:
+    case _table_retry:
+    case _table_trust:
+    case _table_completion:
+      pe = GEN_CP(cptr)->cp_pred_entry;
+      t = BuildActivePred(pe, (CELL *)(GEN_CP(B) + 1));
+      break;
+    case _table_answer_resolution:
+      pe = CONS_CP(cptr)->cp_pred_entry;
+      t = MkVarTerm();
+      break;
+    case _trie_retry_null:
+    case _trie_trust_null:
+    case _trie_retry_var:
+    case _trie_trust_var:
+    case _trie_retry_val:
+    case _trie_trust_val:
+    case _trie_retry_atom:
+    case _trie_trust_atom:
+    case _trie_retry_list:
+    case _trie_trust_list:
+    case _trie_retry_struct:
+    case _trie_trust_struct:
+    case _trie_retry_extension:
+    case _trie_trust_extension:
+    case _trie_retry_float:
+    case _trie_trust_float:
+    case _trie_retry_long:
+    case _trie_trust_long:
+      pe = UndefCode;
+      t = MkVarTerm();
+      break;
+#endif /* TABLING */
+    case _or_else:
+      pe = ipc->u.sla.p0;
+      t = Yap_MkNewApplTerm(FunctorOr, 2);
+      break;
+    case _or_last:
+      pe = ipc->u.p.p;
+      t = Yap_MkNewApplTerm(FunctorOr, 2);
+      break;
+    case _retry2:
+    case _retry3:
+    case _retry4:
+    case _trust_logical_pred:
+      ipc = NEXTOP(ipc,l);
+      go_on = TRUE;
+      break;
+    case _jump:
+      ipc = ipc->u.l.l;
+      go_on = TRUE;
+      break;
+    case _retry_c:
+    case _retry_userc:
+      pe = ipc->u.lds.p;
+      t = BuildActivePred(pe, cptr->cp_args);
+      break;
+    case _retry_profiled:
+    case _count_retry:
+      ipc = NEXTOP(ipc,p);
+      go_on = TRUE;
+      break;
+    case _retry_me:
+    case _trust_me:
+    case _count_retry_me:
+    case _count_trust_me:
+    case _profiled_retry_me:
+    case _profiled_trust_me:
+    case _retry_and_mark:
+    case _profiled_retry_and_mark:
+    case _retry:
+    case _trust:
+      pe = ipc->u.ld.p;
+      t = BuildActivePred(pe, cptr->cp_args);
+      break;
+    case _Nstop:
+    case _Ystop:
+    default:
+      pe = NULL;
+      return FALSE;
+    }
+  }
+  arity = pe->ArityOfPE;
+  if (pe->ModuleOfPred != IDB_MODULE) {
+    if (pe->ModuleOfPred == PROLOG_MODULE) {
+      tmod = TermProlog;
+    } else {
+      tmod = pe->ModuleOfPred;
+    }
+    if (pe->ArityOfPE == 0) {
+      tname = MkAtomTerm((Atom)pe->FunctorOfPred);
+    } else {
+      Functor f = pe->FunctorOfPred;
+      tname = MkAtomTerm(NameOfFunctor(f));
+    }
+  } else {
+    tmod = pe->ModuleOfPred;
+    if (pe->PredFlags & NumberDBPredFlag) {
+      tname = MkIntegerTerm(pe->src.IndxId);
+    } else if (pe->PredFlags & AtomDBPredFlag) {
+      tname = MkAtomTerm((Atom)pe->FunctorOfPred);
+    } else {
+      Functor f = pe->FunctorOfPred;
+      tname = MkAtomTerm(NameOfFunctor(f));
+    }
+  }
+  return Yap_unify(ARG2, tmod) &&
+    Yap_unify(ARG3,tname) &&
+    Yap_unify(ARG4,MkIntegerTerm(arity)) &&
+    Yap_unify(ARG5,t);
+}
+
 void 
 Yap_InitCdMgr(void)
 {
@@ -5367,6 +5519,8 @@ Yap_InitCdMgr(void)
   Yap_InitCPred("$static_pred_statistics", 5, p_static_pred_statistics, SyncPredFlag|HiddenPredFlag);
   Yap_InitCPred("$p_nth_clause", 4, p_nth_clause, SyncPredFlag|HiddenPredFlag);
   Yap_InitCPred("$program_continuation", 3, p_program_continuation, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$all_choicepoints", 1, p_all_choicepoints, HiddenPredFlag);
+  Yap_InitCPred("$choicepoint_info", 5, p_choicepoint_info, HiddenPredFlag);
 #ifdef DEBUG
   Yap_InitCPred("predicate_erased_statistics", 5, p_predicate_erased_statistics, SyncPredFlag);
 #endif

C/exec.c

@@ -1796,6 +1796,8 @@ Yap_InitYaamRegs(void)
   AttsMutableList = Yap_NewTimedVar(MkIntTerm(0));
 #endif
   GcGeneration = Yap_NewTimedVar(MkIntTerm(0));
+  GcCurrentPhase = 0L;
+  GcPhase = Yap_NewTimedVar(MkIntTerm(GcCurrentPhase));
 #if defined(YAPOR) || defined(THREADS)
   PP = NULL;
   WPP = NULL;

C/grow.c

@@ -165,6 +165,7 @@ SetHeapRegs(void)
     WokenGoals = AbsAppl(PtoGloAdjust(RepAppl(WokenGoals)));
 #endif
   GcGeneration = AbsAppl(PtoGloAdjust(RepAppl(GcGeneration)));
+  GcPhase = AbsAppl(PtoGloAdjust(RepAppl(GcPhase)));
 }
 
 static void
@@ -218,6 +219,7 @@ SetStackRegs(void)
     WokenGoals = AbsAppl(PtoGloAdjust(RepAppl(WokenGoals)));
 #endif
   GcGeneration = AbsAppl(PtoGloAdjust(RepAppl(GcGeneration)));
+  GcPhase = AbsAppl(PtoGloAdjust(RepAppl(GcPhase)));
 }
 
 static void

C/heapgc.c

@@ -433,6 +433,8 @@ push_registers(Int num_regs, yamop *nextop)
   }
   TrailTerm(TR) = GcGeneration;
   TR++;
+  TrailTerm(TR) = GcPhase;
+  TR++;
 #ifdef COROUTINING
   TrailTerm(TR) = WokenGoals;
   TrailTerm(TR+1) = AttsMutableList;
@@ -495,6 +497,7 @@ pop_registers(Int num_regs, yamop *nextop)
     sal = sal->NextAE;
   }
   GcGeneration = TrailTerm(ptr++);
+  GcPhase = TrailTerm(ptr++);
 #ifdef COROUTINING
 #ifdef MULTI_ASSIGNMENT_VARIABLES
   WokenGoals = TrailTerm(ptr++);
@@ -3495,6 +3498,7 @@ do_gc(Int predarity, CELL *current_env, yamop *nextop)
   CELL *max;
   Int           effectiveness, tot;
   int           gc_trace;
+  UInt		gc_phase;
 
   heap_cells = H-H0;
   gc_verbose = is_gc_verbose();
@@ -3632,19 +3636,10 @@ do_gc(Int predarity, CELL *current_env, yamop *nextop)
 #endif
   /* get the number of active registers */
   HGEN = H0+IntegerOfTerm(Yap_ReadTimedVar(GcGeneration));
+  gc_phase = (UInt)IntegerOfTerm(Yap_ReadTimedVar(GcPhase));
   /* old HGEN are not very reliable, but still may have data to recover */
-  if (HGEN < HB) {
+  if (gc_phase != GcCurrentPhase) {
-    choiceptr b_ptr = B;
+    HGEN = H0;
-    /* cannot trust the data between HGEN and its current choice-point */
-    while (b_ptr) {
-      if (b_ptr->cp_h <= HGEN) {
-	HGEN = b_ptr->cp_h;
-	break;
-      } else {
-	b_ptr = b_ptr->cp_b;
-      }
-    }
-    if (!b_ptr) HGEN = H0;
   }
   /*  fprintf(stderr,"HGEN is %ld, %p, %p/%p\n", IntegerOfTerm(Yap_ReadTimedVar(GcGeneration)), HGEN, H,H0);*/
 #if !GC_TAGS
@@ -3657,7 +3652,10 @@ do_gc(Int predarity, CELL *current_env, yamop *nextop)
     total_marked -= total_oldies;
     tot = total_marked+(HGEN-H0);
   } else {
-    HGEN = H0;
+    if (HGEN != H0) {
+      HGEN = H0;
+      GcCurrentPhase++;
+    }
     tot = total_marked;
   }
   m_time = Yap_cputime();
@@ -3698,6 +3696,7 @@ do_gc(Int predarity, CELL *current_env, yamop *nextop)
 #endif
   /*  fprintf(Yap_stderr,"NEW HGEN %ld (%ld)\n", H-H0, HGEN-H0);*/
   Yap_UpdateTimedVar(GcGeneration, MkIntegerTerm(H-H0));
+  Yap_UpdateTimedVar(GcPhase, MkIntegerTerm(GcCurrentPhase));
   c_time = Yap_cputime();
   if (gc_verbose) {
     fprintf(Yap_stderr, "%%   Compress: took %g sec\n", (double)(c_time-time_start)/1000);

C/save.c

@@ -423,6 +423,8 @@ save_regs(int mode)
     putout(DEPTH);
 #endif
     putout(GcGeneration);
+    putout(GcPhase);
+    putout(GcCurrentPhase);
   }
   /* The operand base */
   putcellptr(CellPtr(XREGS));
@@ -832,6 +834,12 @@ get_regs(int flag)
     GcGeneration = get_cell();
     if (Yap_ErrorMessage)
       return -1;
+    GcPhase = get_cell();
+    if (Yap_ErrorMessage)
+      return -1;
+    GcCurrentPhase = get_cell();
+    if (Yap_ErrorMessage)
+      return -1;
   }
   /* Get the old bases */
   OldXREGS = get_cellptr();

H/Heap.h

@@ -10,7 +10,7 @@
 * File:		Heap.h         						 *
 * mods:									 *
 * comments:	Heap Init Structure					 *
-* version:      $Id: Heap.h,v 1.91 2006-02-24 14:03:42 vsc Exp $	 *
+* version:      $Id: Heap.h,v 1.92 2006-03-06 14:04:56 vsc Exp $	 *
 *************************************************************************/
 
 /* information that can be stored in Code Space */
@@ -98,6 +98,8 @@ typedef struct worker_local_struct {
 #endif
   /* gc_stuff */
   Term     gc_generation;	/* global stack limit at last generation */ 
+  Term     gc_phase;	        /* gc phase to be sure we are on a valid compression */ 
+  UInt     gc_current_phase;    /* gc currrent phase */ 
   unsigned int      gc_calls;	/* number of times GC has been called */ 
   Int      tot_gc_time; /* total time spent in GC */
   YAP_ULONG_LONG      tot_gc_recovered; /* number of heap objects in all garbage collections */
@@ -785,7 +787,10 @@ struct various_codes *Yap_heap_regs;
 #define  WokenGoals               Yap_heap_regs->wl[worker_id].woken_goals
 #define  AttsMutableList          Yap_heap_regs->wl[worker_id].atts_mutable_list
 #endif
+/* support for generations with backtracking */
 #define  GcGeneration             Yap_heap_regs->wl[worker_id].gc_generation
+#define  GcPhase                  Yap_heap_regs->wl[worker_id].gc_phase
+#define  GcCurrentPhase           Yap_heap_regs->wl[worker_id].gc_current_phase
 #define  GcCalls                  Yap_heap_regs->wl[worker_id].gc_calls
 #define  TotGcTime                Yap_heap_regs->wl[worker_id].tot_gc_time
 #define  TotGcRecovered           Yap_heap_regs->wl[worker_id].tot_gc_recovered
@@ -854,6 +859,8 @@ struct various_codes *Yap_heap_regs;
 #define  AttsMutableList          Yap_heap_regs->wl.atts_mutable_list
 #endif
 #define  GcGeneration             Yap_heap_regs->wl.gc_generation
+#define  GcPhase                  Yap_heap_regs->wl.gc_phase
+#define  GcCurrentPhase           Yap_heap_regs->wl.gc_current_phase
 #define  GcCalls                  Yap_heap_regs->wl.gc_calls
 #define  TotGcTime                Yap_heap_regs->wl.tot_gc_time
 #define  TotGcRecovered           Yap_heap_regs->wl.tot_gc_recovered

H/rheap.h

@@ -11,8 +11,11 @@
 * File:		rheap.h							 *
 * comments:	walk through heap code					 *
 *									 *
-* Last rev:     $Date: 2006-02-24 14:03:42 $,$Author: vsc $						 *
+* Last rev:     $Date: 2006-03-06 14:04:56 $,$Author: vsc $						 *
 * $Log: not supported by cvs2svn $
+* Revision 1.62  2006/02/24 14:03:42  vsc
+* fix refs to old LogUpd implementation (pre 5).
+*
 * Revision 1.61  2006/01/02 02:16:18  vsc
 * support new interface between YAP and GMP, so that we don't rely on our own
 * allocation routines.
@@ -493,6 +496,11 @@ restore_codes(void)
     Yap_heap_regs->wl.scratchpad.ptr =
       (char *)AddrAdjust((ADDR)Yap_heap_regs->wl.scratchpad.ptr);
   }
+  Yap_heap_regs->wl.gc_generation = 
+    AbsAppl(PtoGloAdjust(RepAppl(Yap_heap_regs->wl.gc_generation)));
+  Yap_heap_regs->wl.gc_phase = 
+    AbsAppl(PtoGloAdjust(RepAppl(Yap_heap_regs->wl.gc_phase)));
+  /* current phase is an integer */
 #endif
 #ifdef COROUTINING
   if (Yap_heap_regs->wake_up_code != NULL)

changes-5.1.html

@@ -16,41 +16,49 @@
 
 <h2>Yap-5.1.0:</h2>
 <ul>
+<li> NEW: debugger will not backtrack over complete deterministic computations.</li>
+<li> NEW: debugger can show CP stack.</li>
+<li> NEW: internal procedure to show choice-point stack.</li>
+<li> FIXED: Incremental GC could still get confused after backtracking
+  over GEN marker. Associate GEN marker with timestamp and make sure
+  we only use current GEN markers (obs Mark Goadrich).</li>
 <li> FIXED: Yap on OSX should not make CreepFlag a register, as this
   breaks Interrupt Handling. Also, it seems that if I do not reserve
   r13, GCC will use r14 for its own evil purposes.</li>
-<li> FIXED: make Yap files usable again as a script (Ales Kozumplik).</li>
+<li> FIXED: make Yap files usable again as a script (obs Ales Kozumplik).</li>
-<li> FIXED: informational_messages was being ignored (Nicos Angelopoulos).</li>
+<li> FIXED: silent informational_messages was being ignored (obs Nicos Angelopoulos).</li>
 <li> FIXED: initialization should only be performed after all
   consulted files are done.</li>
 <li> FIXED: garbage collector now makes refs to erased LU clauses point
   to LogUpdErasedMarker.</li>
 <li> FIXED: get rid of old code referring to LogUpds from within ImmediateSemantics.</li>
 <li> FIXED: indexing code would get confused about size of inlined
-float/1 (Paulo Moura).</li>
+float/1 (obs Paulo Moura).</li>
 <li> FIXED: broken SIGINT with tkyap (Keri Harris).</li>
 <li> FIXED: indexing of bignums was broken, just disable it for now.</li>
-<li> FIXED: pipe open was returning the same descriptor twice (Christian Thaeter).</li>
+<li> FIXED: pipe open was returning the same descriptor twice (obs Christian Thaeter).</li>
 <li> FIXED: style check should compare with true file name.</li>
 <li> FIXED: ^c should take care about TR and B.</li>
-<li> FIXED: don't pass a pointer to a mpz_t. (Nuno Fonseca)</li>
+<li> FIXED: don't pass a pointer to a mpz_t. (obs Nuno Fonseca)</li>
-<li> FIXED: handle heap overflow from huge atoms in Yap_LookupAtom/scanner (Nuno Fonseca).</li>
+<li> FIXED: handle heap overflow from huge atoms in
-<li> FIXED: bignum was using int where should be long int (Roberto Bagnara).</li>
+  Yap_LookupAtom/scanner (obs Nuno Fonseca).</li>
+<li> FIXED: bignum was using int where should be long int (obs Roberto Bagnara).</li>
 <li> NEW: x86_64 should have registers, right? First cut at using them.</li>
 <li> FIXED: call_n would break under 64 bits, an int problem.</li>
-<li> FIXED: more compilation problems if GMP not there (Remko Troncon).</li>
+<li> FIXED: more compilation problems if GMP not there (obs Remko Troncon).</li>
-<li> FIXED: make syntax error report the line where the bug was (Jude Shavlik).</li>
+<li> FIXED: make syntax error report the line where the bug was (obs Jude Shavlik).</li>
 <li> FIXED: ok, MkBigInt shouldn't free the bigint.</li>
 <li> FIXED: MkBigInt already frees bigint.</li>
-<li> FIXED: don't pass a pointer to a mpz_t. (Nuno Fonseca)</li>
+<li> FIXED: don't pass a pointer to a mpz_t. (obs Nuno Fonseca)</li>
-<li> FIXED: YENV may be an HW register (could break some tabling code)  (Remko Troncon) </li>
+<li> FIXED: YENV may be an HW register (could break some tabling code)
+  (obs Remko Troncon) </li>
 <li> FIXED: All YAAM instructions are now brackedted, so Op introduced an { and EndOp intr
 oduces an }. This is because Ricardo assumes that. </li>
 <li> FIXED: compile attvars when COROUTING is undefined. </li>
 <li> FIXED: compiler warnings due to c-interface changes</li>.
 <li> FIXED: scanner would convert LONG_MIN to bigint, but it can be
-  represent as a LONG; fixed by using mpz_fits_slong_p (Roberto Bagnara). </li>
+  represent as a LONG; fixed by using mpz_fits_slong_p (obs Roberto Bagnara). </li>
-<li> FIXED: indexing cut should stop looking after a cut!!!! (Paulo Moura).
+<li> FIXED: indexing cut should stop looking after a cut!!!! (obs Paulo Moura).
 <li> FIXED: mktime was broken in WIN32. </li>
 <li> FIXED: don't assume a fixed point for WIN32 memory allocation. </li>
 <li> FIXED: don't call goal_expand when looking for handlers of undefined procedures. </li>
@@ -151,7 +159,7 @@ discontiguous. </li>
 <li> FIXED: save/restore FZ regs. </li>
 <li> FIXED: $loop_stream could be defined early in boot process. </li>
 <li> NEW: make rational trees default. </li>
-<li> NEW: make enable-max-memory default. </li>
+v<li> NEW: make enable-max-memory default. </li>
 <li> FIXED: allow people to disable indexing (obs Ricardo Lopes). </li>
 <li> FIXED: make undefined exception more ISO like (obs Paulo Moura). </li>
 <li> FIXED: add missing dependency in chr's Makefile.in. </li>

docs/yap.tex

@@ -10258,9 +10258,10 @@ and it includes four or five fields:
 
 @itemize @bullet
 @item
- The first two characters are used to point out special states of the
+ The first three characters are used to point out special states of the
-debugger. If the first character is a @code{*}, execution is at a
+debugger. If the port is exit and the first character is '?', the
-spy-point. If the second character is a @code{>}, execution has returned
+current call still has alternatives to be tried. If the second character is a @code{*}, execution is at a
+spy-point. If the third character is a @code{>}, execution has returned
 either from a skip, a fail or a redo command.
 @item
  The second field is the activation number, and uniquely identifies the
@@ -10343,6 +10344,8 @@ information about @code{write_depth/2} (@pxref{I/O Control}).
 @item < - full term
 resets to the default of ten the debugger's maximum write depth. For
 more information about @code{write_depth/2} (@pxref{I/O Control}).
+@item A - alternatives
+ show the list of backtrack points in the current execution. 
 @end table
 
 The debugging information, when fast-skip @code{quasi-leap} is used, will

pl/debug.yap

@@ -318,7 +318,8 @@ debugging :-
 % we are skipping, so we can just call the goal,
 % while leaving the minimal structure in place.
 '$loop_spy'(GoalNumber, G, Module, InControl) :-
-    '$system_catch'('$loop_spy2'(GoalNumber, G, Module, InControl),
+	CP is '$last_choice_pt',
+	'$system_catch'('$loop_spy2'(GoalNumber, CP, G, Module, InControl),
 		    Module, Event,
 		    '$loop_spy_event'(Event, GoalNumber, G, Module, InControl)).
 
@@ -357,7 +358,7 @@ debugging :-
 		    '$loop_spy_event'(Event, GoalNumber, G, Module, InControl)).
 
 % if we are in 
-'$loop_spy2'(GoalNumber, G, Module, InControl) :- 
+'$loop_spy2'(GoalNumber, CP, G, Module, InControl) :- 
 /* the following choice point is where the predicate is  called */
 	(
 	/* call port */
@@ -366,10 +367,11 @@ debugging :-
 	/* go execute the predicate	*/
 	    (
 	       '$do_not_creep',
-	       '$show_trace'(exit,G,Module,GoalNumber),	/* output
+	       '$show_trace'(exit,G,Module,GoalNumber),	/* output message at exit	*/
-	       message at exit	*/
 	       /* exit port */
-	       '$continue_debugging'	       
+	       /* get rid of deterministic computations */
+	        ('$debugger_deterministic_goal'(G) ->  '$cut_by'(CP) ; true),
+	       '$continue_debugging'	   
 	     ;
 		/* backtracking from exit				*/
 	        /* we get here when we want to redo a goal		*/
@@ -448,14 +450,15 @@ debugging :-
 	flush_output(user_error),
 	recorded('$debug',on,R0), erase(R0),
 	repeat,
+	        (P = exit, \+ '$debugger_deterministic_goal'(G) -> Det = '?' ; Det = ''),
 		('$pred_being_spied'(G,Module) -> CSPY = '*' ; CSPY = ' '),
 		( SL = L -> SLL = '>' ; SLL = ' '),
 	        ( recorded('$debug',on, R), erase(R), fail ; true),
 		( Module\=prolog,
 		  Module\=user ->
-		    format(user_error,"~a~a (~d) ~q: ~a:",[CSPY,SLL,L,P,Module])
+		    format(user_error,"~a~a~a       (~d)    ~q: ~a:",[Det,CSPY,SLL,L,P,Module])
 		    ;
-		    format(user_error,"~a~a (~d) ~q:",[CSPY,SLL,L,P])
+		    format(user_error,"~a~a~a       (~d)    ~q:",[Det,CSPY,SLL,L,P])
 		),
 		'$debugger_write'(user_error,G),
 	        ( nonvar(R0), recordaifnot('$debug',on,_), fail ; true),
@@ -503,12 +506,16 @@ debugging :-
 	'$skipeol'(0'^),
 	fail.
 '$action'(0'a,_,_,_,_) :- !,			% a		abort
-	'$skipeol'(0'^),
+	'$skipeol'(0'a),
 	abort.
 '$action'(0'b,_,_,_,_) :- !,			% b		break
 	'$skipeol'(0'b),
 	break,
 	fail.
+'$action'(0'A,_,_,_,_) :- !,			% b		break
+	'$skipeol'(0'A),
+	'$show_choicepoint_stack',
+	fail.
 '$action'(0'c,_,_,_,_) :- !,			% c		creep
 	'$set_yap_flags'(10,1),
 	'$skipeol'(0'c).
@@ -618,6 +625,7 @@ debugging :-
 	format(user_error,"<D       depth D     <       full term~n", []),
 	format(user_error,"+        spy this    -       nospy this~n", []),
 	format(user_error,"^        view subg   ^^      view using~n", []),
+	format(user_error,"A        alternatives~n", []),
 	format(user_error,"! g execute goal~n", []).
 	
 '$ilgl'(C) :-
@@ -712,3 +720,52 @@ debugging :-
 '$delete_if_there'([Q|L], T, [Q|LN]) :-
 	'$delete_if_there'(L, T, LN).
 
+'$show_choicepoint_stack' :-
+	'$all_choicepoints'(Cps),
+	length(Cps,Level),
+	'$debug_show_cps'(Cps,Level).
+
+'$debug_show_cps'([],_).
+'$debug_show_cps'([C|Cps],Level) :-
+	'$debug_show_cp'(C, Level),
+	Level1 is Level-1,
+	'$debug_show_cps'(Cps, Level1).
+
+'$debug_show_cp'(C, Level) :-
+	'$choicepoint_info'(C,Module,Name,Arity,Goal),
+	'$continue_debug_show_cp'(Module,Name,Arity,Goal,Level).
+
+'$continue_debug_show_cp'(prolog,'$do_live',0,(_;_),Level) :- !,
+	format(user_error,'      [~d] \'$toplevel\'',[Level]).
+'$continue_debug_show_cp'(prolog,'$do_log_upd_clause',4,'$do_log_upd_clause'(_,_,Goal,_),Level) :- !,
+	format(user_error,'      [~d] ~q~n',[Level,Goal]).
+'$continue_debug_show_cp'(prolog,'$do_static_clause',5,'$do_static_clause'(_,_,Goal,_,_),Level) :- !,
+	format(user_error,'      [~d] ~q~n',[Level,Goal]).
+'$continue_debug_show_cp'(Module,Name,Arity,Goal,_) :-
+	functor(G0, Name, Arity), fail,
+	'$hidden_predicate'(G0,Module),
+	!.
+'$continue_debug_show_cp'(Module,Name,Arity,Goal,Level) :-
+	var(Goal), !,
+	format(user_error,'      [~d] ~q:~q/~d~n',[Level,Module,Name,Arity]).
+'$continue_debug_show_cp'(Module,Name,Arity,(V1;V2),Level) :-
+	var(V1),  var(V2), !,
+	format(user_error,'      [~d] ~q:~q/~d: ;/2~n',[Level,Module,Name,Arity]).
+'$continue_debug_show_cp'(Module,Name,Arity,G,Level) :-
+	format(user_error,'      [~d] ~q~n',[Level,G]).
+	
+'$debugger_deterministic_goal'(G) :-
+	'$all_choicepoints'(CPs),
+	'$debugger_check_traces'(CPs,CPs1),
+	'$debugger_check_loop_spy2'(CPs1,[Catch|_]),
+	'$choicepoint_info'(Catch,prolog,'$catch',3,'$catch'(_,'$loop_spy_event'(_,_,G,_,_),_)).
+
+'$debugger_check_traces'([CP|CPs],CPs1) :-
+	'$choicepoint_info'(CP,prolog,'$trace',4,(_;_)), !,
+	'$debugger_check_traces'(CPs,CPs1).
+'$debugger_check_traces'(CPs,CPs).
+
+'$debugger_check_loop_spy2'([CP|CPs],CPs1) :-
+	'$choicepoint_info'(CP,prolog,'$loop_spy2',5,(_;_)), !,
+	'$debugger_check_loop_spy2'(CPs,CPs1).
+'$debugger_check_loop_spy2'(CPs,CPs).