Files
mercury/browser/declarative_analyser.m
Julien Fischer 459847a064 Move the univ, maybe, pair and unit types from std_util into their own
Estimated hours taken: 18
Branches: main

Move the univ, maybe, pair and unit types from std_util into their own
modules.  std_util still contains the general purpose higher-order programming
constructs.

library/std_util.m:
	Move univ, maybe, pair and unit (plus any other related types
	and procedures) into their own modules.

library/maybe.m:
	New module.  This contains the maybe and maybe_error types and
	the associated procedures.

library/pair.m:
	New module.  This contains the pair type and associated procedures.

library/unit.m:
	New module. This contains the types unit/0 and unit/1.

library/univ.m:
	New module. This contains the univ type and associated procedures.

library/library.m:
	Add the new modules.

library/private_builtin.m:
	Update the declaration of the type_ctor_info struct for univ.

runtime/mercury.h:
	Update the declaration for the type_ctor_info struct for univ.

runtime/mercury_mcpp.h:
runtime/mercury_hlc_types.h:
	Update the definition of MR_Univ.

runtime/mercury_init.h:
	Fix a comment: ML_type_name is now exported from type_desc.m.

compiler/mlds_to_il.m:
	Update the the name of the module that defines univs (which are
	handled specially by the il code generator.)

library/*.m:
compiler/*.m:
browser/*.m:
mdbcomp/*.m:
profiler/*.m:
deep_profiler/*.m:
	Conform to the above changes.  Import the new modules where they
	are needed; don't import std_util where it isn't needed.

	Fix formatting in lots of modules.  Delete duplicate module
	imports.

tests/*:
	Update the test suite to confrom to the above changes.
2006-03-29 08:09:58 +00:00

1363 lines
54 KiB
Mathematica

%-----------------------------------------------------------------------------%
% vim: ft=mercury ts=4 sw=4 et
%-----------------------------------------------------------------------------%
% Copyright (C) 1999-2006 The University of Melbourne.
% This file may only be copied under the terms of the GNU Library General
% Public License - see the file COPYING.LIB in the Mercury distribution.
%-----------------------------------------------------------------------------%
%
% File: declarative_analyser.m
% Authors: Mark Brown, Ian MacLarty
%
% This module implements some analysis algorithms that search for bugs in
% Evaluation Dependency Trees (EDTs). The search algorithms use information
% provided by the search_space data type which acts as a layer on top of the
% EDT, storing information relevant to the bug search. Throughout this module
% the type variables T and S refer to the types of nodes in the EDT and the
% store of EDT nodes respectively.
%-----------------------------------------------------------------------------%
:- module mdb.declarative_analyser.
:- interface.
:- import_module mdb.declarative_debugger.
:- import_module mdb.declarative_edt.
:- import_module mdb.declarative_oracle.
:- import_module mdb.declarative_user.
:- import_module io.
:- import_module maybe.
%-----------------------------------------------------------------------------%
:- type analyser_response(T)
---> no_suspects
% There are no suspects left, and no incorrect
% nodes have been found.
; bug_found(decl_bug, decl_evidence(T))
% A suspect who is guilty, along with the evidence
% against the suspect.
; oracle_question(decl_question(T))
% The analyser desires an answer to the question.
; require_explicit_subtree(T)
% The analyser requires the given implicit sub-tree
% to be made explicit.
; require_explicit_supertree(T)
% The analyser requires an explicit tree above the
% root of an existing explicit tree.
; revise(decl_question(T)).
% The analyser would like the oracle to re-ask the user
% this question and then for analysis to continue.
:- func reason_to_string(reason_for_question) = string.
:- type analyser_state(T).
:- type search_mode.
:- func divide_and_query_search_mode = search_mode.
:- func suspicion_divide_and_query_search_mode = search_mode.
:- func top_down_search_mode = search_mode.
:- pred analyser_state_init(analyser_state(T)::out) is det.
% Resets the state of the analyser.
%
:- pred reset_analyser(analyser_state(T)::in, analyser_state(T)::out) is det.
% Make the given search mode the fallback search mode
% and the current search mode for the analyser.
%
:- pred set_fallback_search_mode(S::in, search_mode::in,
analyser_state(T)::in, analyser_state(T)::out)
is det <= mercury_edt(S, T).
:- type analysis_type(T)
---> new_tree(T)
% Use the given tree to do analysis. The tree will be
% a new explicitly generated portion of the annotated
% trace. start_or_resume_analysis should be called
% with this type of analysis when a new declarative
% debugging session has been started or a requested
% subtree or supertree has been generated.
; resume_previous.
% Continue the previous analysis. This will happen
% when the user suspends a declarative debugging
% session with a `pd' or `abort' command and now wants
% to continue the suspended session.
% Perform analysis on the given EDT, which may be a new tree
% to diagnose, or a sub-tree that was required to be made explicit.
%
:- pred start_or_resume_analysis(S::in, oracle_state::in, analysis_type(T)::in,
analyser_response(T)::out, analyser_state(T)::in,
analyser_state(T)::out) is det <= mercury_edt(S, T).
% Return a response which will cause the last question to be re-asked.
%
:- pred reask_last_question(S::in, analyser_state(T)::in,
analyser_response(T)::out) is semidet <= mercury_edt(S, T).
% Continue analysis after the oracle has responded with an answer.
%
:- pred continue_analysis(S::in, oracle_state::in, decl_answer(T)::in,
analyser_response(T)::out, analyser_state(T)::in,
analyser_state(T)::out) is det <= mercury_edt(S, T).
% Change the current search mode of the analyser and return the
% next question using the new search mode.
%
:- pred change_search_mode(S::in, oracle_state::in, user_search_mode::in,
analyser_state(T)::in, analyser_state(T)::out,
analyser_response(T)::out) is det <= mercury_edt(S, T).
% Display information about the current question and the state
% of the search to the supplied output stream.
%
:- pred show_info(S::in, io.output_stream::in, analyser_state(T)::in,
io::di, io::uo) is det <= mercury_edt(S, T).
% Revise the current analysis. This is done when a bug determined
% by the analyser has been overruled by the oracle.
%
:- pred revise_analysis(S::in, analyser_response(T)::out,
analyser_state(T)::in, analyser_state(T)::out) is det <= mercury_edt(S, T).
% Return information within the analyser state that is intended for
% debugging the declarative debugger itself.
%
:- pred debug_analyser_state(analyser_state(T)::in,
maybe(subterm_origin(T))::out) is det.
%-----------------------------------------------------------------------------%
%-----------------------------------------------------------------------------%
:- implementation.
:- import_module mdb.browser_info.
:- import_module mdb.declarative_edt.
:- import_module mdb.declarative_execution.
:- import_module mdbcomp.prim_data.
:- import_module mdbcomp.program_representation.
:- import_module mdbcomp.rtti_access.
:- import_module array.
:- import_module bool.
:- import_module counter.
:- import_module exception.
:- import_module float.
:- import_module int.
:- import_module list.
:- import_module map.
:- import_module math.
:- import_module pair.
:- import_module string.
:- import_module unit.
%-----------------------------------------------------------------------------%
% Describes what search strategy is being used by the analyser and the
% state of the search.
%
:- type search_mode
---> top_down
% Look for the first unknown suspect in a top-down
% fashion, starting at the root. If no unknown
% suspects are found then choose a skipped suspect
% to requery.
; follow_subterm_end(
% Follow the subterm all the way to where it's bound or
% until it can't be followed any further (for example
% when there is a call to a module with no tracing),
% and ask a question about the nearest unknown suspect
% on the subterm dependency chain. Then proceed to do
% a binary search between this node and the root of the
% search space (the binary search will only come into
% effect if the oracle asserts the suspect is correct
% or inadmissible).
suspect_id,
arg_pos,
term_path,
% The above 3 args give the position the sub-term tracking
% algorithm has got up to if it needs to stop to wait for
% an explicit sub/super-tree to be generated.
maybe(suspect_id),
% The last suspect on the dependency chain
% whose status was unknown. Initially this is
% no, but as the sub-term is tracked to where
% it was initially bound (which could be above
% or below the node where it was marked
% incorrect), the most recent node through
% which the sub-term was tracked that has a
% status of `unknown' is stored in this field.
% This is then used as the next question if the
% node that bound the sub-term is trusted or in
% an excluded part of the search tree.
how_track_subterm
% This field specifies the algorithm to use
% when tracking the subterm.
)
; binary(
% Perform a binary search on a path in the search space
% between a suspect and an ancestor of the suspect.
% The path is represented as an array (the 1st
% argument) with the deeper suspect at the end of the
% array and its ancestor at the beginning.
% The range field gives the inclusive subrange of the
% array to search. last_tested is the index into the
% array of the last suspect about which a question was
% asked.
suspects :: array(suspect_id),
range :: pair(int, int),
last_tested :: int
)
; divide_and_query(weighting_heuristic).
% Divide and query using the given weighting
% heuristic.
divide_and_query_search_mode = divide_and_query(number_of_events).
suspicion_divide_and_query_search_mode = divide_and_query(suspicion).
top_down_search_mode = top_down.
% Each search algorithm should respond with either a question
% or a request for an explicit subtree to be generated for a suspect
% which is the root of an implicit subtree.
%
:- type search_response
---> question(suspect_id, reason_for_question)
; require_explicit_subtree(suspect_id)
; require_explicit_supertree
; no_suspects
; found_bug(suspect_id, list(suspect_id), list(suspect_id)).
% The reason the declarative debugger asked a question.
%
:- type reason_for_question
---> start
% The first question.
; top_down
; binding_node(
binding_prim_op :: primitive_op_type,
binding_filename :: string,
binding_line_no :: int,
maybe_atom_path :: maybe(term_path),
% The path of the subterm in the
% binding node, if it appears in the
% binding node's atom.
binding_proc :: proc_label,
binding_node_eliminated :: bool
)
; subterm_no_proc_rep
% No proc rep when tracking subterm.
; binding_node_eliminated
; binary(
binary_reason_bottom :: int,
binary_reason_top :: int,
binary_reason_split :: int
)
; divide_and_query(
dq_weighting :: weighting_heuristic,
dq_old_weight :: int,
% The weight of the search space before
% the question was asked.
dq_chosen_subtree_weight :: int
% The weight the searchspace will be
% if the user answers `no' to the
% current question.
)
; skipped
; revise.
% The analyser state records all of the information that needs
% to be remembered across multiple invocations of the analyser.
%
:- type analyser_state(T)
---> analyser(
% Information about the EDT nodes relevent to
% the bug search.
search_space :: search_space(T),
% This is set to yes when an explicit tree needs to be
% generated. The maybe argument says what type of explicit
% tree needs to be generated.
require_explicit :: maybe(explicit_tree_type),
% The method currently being employed to search
% the search space for questions for the
% oracle.
search_mode :: search_mode,
% The search mode to use by default.
% Only non-parametrized search modes should
% be used as the fallback search mode.
fallback_search_mode :: search_mode,
% Everytime a search finds a suspect to ask the oracle
% about it is put in this field before asking the oracle,
% so the analyser knows how to modify the search space when
% it gets an answer.
last_search_question :: maybe(suspect_and_reason),
% This field is present only to make it easier
% to debug the dependency tracking algorithm;
% if bound to yes, it records the result of
% the invocation of that algorithm on the last
% analysis step.
debug_origin :: maybe(subterm_origin(T))
).
:- type suspect_and_reason
---> suspect_and_reason(suspect_id, reason_for_question).
:- type explicit_tree_type
---> explicit_subtree(suspect_id)
% Generate an explicit subtree for the implicit root
% referenced by the suspect_id.
; explicit_supertree.
% Generate a new explicit tree above the current
% explicit tree.
analyser_state_init(Analyser) :-
Analyser = analyser(empty_search_space, no, top_down, top_down, no, no).
reset_analyser(!Analyser) :-
FallBack = !.Analyser ^ fallback_search_mode,
!:Analyser = analyser(empty_search_space, no, FallBack, FallBack, no, no).
set_fallback_search_mode(Store, FallBackSearchMode, !Analyser) :-
!:Analyser = !.Analyser ^ fallback_search_mode := FallBackSearchMode,
!:Analyser = !.Analyser ^ search_mode := FallBackSearchMode,
!:Analyser = !.Analyser ^ last_search_question := no,
( FallBackSearchMode = divide_and_query(Weighting) ->
SearchSpace0 = !.Analyser ^ search_space,
update_weighting_heuristic(Store, Weighting, SearchSpace0,
SearchSpace),
!:Analyser = !.Analyser ^ search_space := SearchSpace
;
true
).
debug_analyser_state(Analyser, Analyser ^ debug_origin).
start_or_resume_analysis(Store, Oracle, AnalysisType, Response, !Analyser) :-
(
AnalysisType = new_tree(Node),
MaybeRequireExplicit = !.Analyser ^ require_explicit,
(
MaybeRequireExplicit = yes(TreeType),
SearchSpace0 = !.Analyser ^ search_space,
(
TreeType = explicit_supertree,
incorporate_explicit_supertree(Store, Oracle, Node,
SearchSpace0, SearchSpace)
;
TreeType = explicit_subtree(SuspectId),
incorporate_explicit_subtree(SuspectId, Node,
SearchSpace0, SearchSpace)
),
!:Analyser = !.Analyser ^ search_space := SearchSpace,
!:Analyser = !.Analyser ^ require_explicit := no,
decide_analyser_response(Store, Oracle, Response, !Analyser)
;
MaybeRequireExplicit = no,
%
% An explicit subtree was not requested, so this is the
% start of a new declarative debugging session.
%
reset_analyser(!Analyser),
MaybeWeighting = get_maybe_weighting_from_search_mode(
!.Analyser ^ search_mode),
initialise_search_space(Store, MaybeWeighting, Node, SearchSpace),
!:Analyser = !.Analyser ^ search_space := SearchSpace,
topmost_det(SearchSpace, TopMostId),
!:Analyser = !.Analyser ^ last_search_question :=
yes(suspect_and_reason(TopMostId, start)),
edt_question(Store, Node, Question),
Response = revise(Question)
)
;
AnalysisType = resume_previous,
( reask_last_question(Store, !.Analyser, Response0) ->
Response = Response0
;
decide_analyser_response(Store, Oracle, Response, !Analyser)
)
).
:- func get_maybe_weighting_from_search_mode(search_mode) =
maybe(weighting_heuristic).
get_maybe_weighting_from_search_mode(divide_and_query(Weighting)) =
yes(Weighting).
get_maybe_weighting_from_search_mode(top_down) = no.
get_maybe_weighting_from_search_mode(binary(_, _, _)) = no.
get_maybe_weighting_from_search_mode(follow_subterm_end(_, _, _, _, _)) = no.
reask_last_question(Store, Analyser, Response) :-
MaybeLastQuestion = Analyser ^ last_search_question,
MaybeLastQuestion = yes(suspect_and_reason(SuspectId, _)),
SearchSpace = Analyser ^ search_space,
Node = get_edt_node(SearchSpace, SuspectId),
edt_question(Store, Node, OracleQuestion),
Response = oracle_question(OracleQuestion).
continue_analysis(Store, Oracle, Answer, Response, !Analyser) :-
(
!.Analyser ^ last_search_question = yes(
suspect_and_reason(SuspectId, _)),
process_answer(Store, Answer, SuspectId, !Analyser)
;
!.Analyser ^ last_search_question = no,
throw(internal_error("continue_analysis",
"received answer to unasked question"))
),
decide_analyser_response(Store, Oracle, Response, !Analyser).
change_search_mode(Store, Oracle, UserMode, !Analyser, Response) :-
(
UserMode = top_down,
set_fallback_search_mode(Store, top_down, !Analyser)
;
UserMode = divide_and_query,
set_fallback_search_mode(Store,
divide_and_query(number_of_events), !Analyser)
;
UserMode = suspicion_divide_and_query,
set_fallback_search_mode(Store, divide_and_query(suspicion), !Analyser)
;
UserMode = binary,
(
!.Analyser ^ last_search_question =
yes(suspect_and_reason(SuspectId, _)),
setup_binary_search(!.Analyser ^ search_space, SuspectId,
SearchMode),
!:Analyser = !.Analyser ^ search_mode := SearchMode
;
!.Analyser ^ last_search_question = no,
throw(internal_error("change_search_mode",
"binary mode requested, but no last question"))
)
),
decide_analyser_response(Store, Oracle, Response, !Analyser).
:- pred process_answer(S::in, decl_answer(T)::in, suspect_id::in,
analyser_state(T)::in, analyser_state(T)::out) is det <= mercury_edt(S, T).
process_answer(_, skip(_), SuspectId, !Analyser) :-
skip_suspect(SuspectId, !.Analyser ^ search_space, SearchSpace),
!:Analyser = !.Analyser ^ search_space := SearchSpace.
process_answer(Store, ignore(_), SuspectId, !Analyser) :-
ignore_suspect(Store, SuspectId, !.Analyser ^ search_space, SearchSpace),
!:Analyser = !.Analyser ^ search_space := SearchSpace.
process_answer(_, truth_value(_, correct), SuspectId, !Analyser) :-
assert_suspect_is_correct(SuspectId, !.Analyser ^ search_space,
SearchSpace),
!:Analyser = !.Analyser ^ search_space := SearchSpace.
process_answer(_, truth_value(_, inadmissible), SuspectId, !Analyser) :-
assert_suspect_is_inadmissible(SuspectId, !.Analyser ^ search_space,
SearchSpace),
!:Analyser = !.Analyser ^ search_space := SearchSpace.
process_answer(_, truth_value(_, erroneous), SuspectId, !Analyser) :-
assert_suspect_is_erroneous(SuspectId, !.Analyser ^ search_space,
SearchSpace),
!:Analyser = !.Analyser ^ search_space := SearchSpace.
process_answer(Store, suspicious_subterm(Node, ArgPos, TermPath, HowTrack,
ShouldAssertInvalid), SuspectId, !Analyser) :-
%
% XXX The following 2 lines just done so that debugging info can be
% printed for tests run when declarative_analyser.m not compiled with
% tracing (so can't use dd_dd command in mdb). Should be removed when
% edt_dependency becomes stable enough.
%
edt_dependency(Store, Node, ArgPos, TermPath, _, DebugOrigin),
!:Analyser = !.Analyser ^ debug_origin := yes(DebugOrigin),
(
ShouldAssertInvalid = assert_invalid,
edt_subterm_mode(Store, Node, ArgPos, TermPath, Mode),
(
Mode = subterm_in,
assert_suspect_is_inadmissible(SuspectId,
!.Analyser ^ search_space, SearchSpace)
;
Mode = subterm_out,
assert_suspect_is_erroneous(SuspectId,
!.Analyser ^ search_space, SearchSpace)
),
!:Analyser = !.Analyser ^ search_space := SearchSpace
;
ShouldAssertInvalid = no_assert_invalid
),
!:Analyser = !.Analyser ^ search_mode := follow_subterm_end(SuspectId,
ArgPos, TermPath, no, HowTrack).
revise_analysis(Store, Response, !Analyser) :-
SearchSpace = !.Analyser ^ search_space,
( root(SearchSpace, RootId) ->
Node = get_edt_node(!.Analyser ^ search_space, RootId),
edt_question(Store, Node, Question),
Response = revise(Question),
revise_root(Store, SearchSpace, SearchSpace1),
!:Analyser = !.Analyser ^ search_space := SearchSpace1,
!:Analyser = !.Analyser ^ last_search_question :=
yes(suspect_and_reason(RootId, revise)),
!:Analyser = !.Analyser ^ search_mode :=
!.Analyser ^ fallback_search_mode
;
% There must be a root, since a bug was found (and is now
% being revised).
throw(internal_error("revise_analysis", "no root"))
).
:- pred decide_analyser_response(S::in, oracle_state::in,
analyser_response(T)::out, analyser_state(T)::in,
analyser_state(T)::out) is det <= mercury_edt(S, T).
decide_analyser_response(Store, Oracle, Response, !Analyser) :-
maybe_check_search_space_consistency(Store, !.Analyser ^ search_space,
"Start of decide_analyser_response"),
some [!SearchSpace] (
!:SearchSpace = !.Analyser ^ search_space,
search(Store, Oracle, !SearchSpace, !.Analyser ^ search_mode,
!.Analyser ^ fallback_search_mode, NewMode, SearchResponse),
!:Analyser = !.Analyser ^ search_space := !.SearchSpace,
!:Analyser = !.Analyser ^ search_mode := NewMode,
handle_search_response(Store, SearchResponse, !Analyser, Response)
),
maybe_check_search_space_consistency(Store, !.Analyser ^ search_space,
"End of decide_analyser_response").
:- pred handle_search_response(S::in, search_response::in,
analyser_state(T)::in, analyser_state(T)::out,
analyser_response(T)::out) is det <= mercury_edt(S, T).
handle_search_response(Store, question(SuspectId, Reason), !Analyser,
Response) :-
SearchSpace = !.Analyser ^ search_space,
Node = get_edt_node(SearchSpace, SuspectId),
edt_question(Store, Node, OracleQuestion),
(
(
suspect_unknown(SearchSpace, SuspectId)
;
suspect_skipped(SearchSpace, SuspectId)
)
->
Response = oracle_question(OracleQuestion)
;
suspect_ignored(SearchSpace, SuspectId)
->
% Searches should not respond with questions about suspects we
% already know to be trusted.
throw(internal_error("handle_search_response",
"search responded with query about ignored suspect"))
;
% We already known something about this suspect, but the search
% wants the oracle to be requeried. This may happen if the
% search thinks the user might have answered the question
% incorrectly before.
Response = revise(OracleQuestion)
),
!:Analyser = !.Analyser ^ last_search_question :=
yes(suspect_and_reason(SuspectId, Reason)).
handle_search_response(_, require_explicit_subtree(SuspectId), !Analyser,
Response) :-
!:Analyser = !.Analyser ^ require_explicit := yes(explicit_subtree(
SuspectId)),
Node = get_edt_node(!.Analyser ^ search_space, SuspectId),
Response = require_explicit_subtree(Node).
handle_search_response(_, require_explicit_supertree, !Analyser, Response) :-
!:Analyser = !.Analyser ^ require_explicit := yes(explicit_supertree),
SearchSpace = !.Analyser ^ search_space,
topmost_det(SearchSpace, TopMostId),
TopMost = get_edt_node(SearchSpace, TopMostId),
Response = require_explicit_supertree(TopMost).
handle_search_response(_, no_suspects, !Analyser, no_suspects).
handle_search_response(Store, found_bug(BugId, CorrectDescendents,
InadmissibleChildren), !Analyser, Response) :-
bug_response(Store, !.Analyser ^ search_space, BugId,
[BugId | CorrectDescendents], InadmissibleChildren, Response).
% bug_response(Store, SearchSpace, BugId, Evidence,
% InadmissibleChildren, Response)
% Create a bug analyser-response using the given Evidence. If
% InadmissibleChildren isn't empty then an i_bug will be created,
% otherwise an e_bug will be created.
%
:- pred bug_response(S::in, search_space(T)::in,
suspect_id::in, list(suspect_id)::in, list(suspect_id)::in,
analyser_response(T)::out) is det <= mercury_edt(S, T).
bug_response(Store, SearchSpace, BugId, Evidence, InadmissibleChildren,
Response) :-
BugNode = get_edt_node(SearchSpace, BugId),
(
InadmissibleChildren = [InadmissibleChild | _],
edt_get_i_bug(Store, BugNode,
get_edt_node(SearchSpace, InadmissibleChild), IBug),
Bug = i_bug(IBug)
;
InadmissibleChildren = [],
edt_get_e_bug(Store, BugNode, EBug),
Bug = e_bug(EBug)
),
EDTNodes = list.map(get_edt_node(SearchSpace), Evidence),
list.map(edt_question(Store), EDTNodes,
EvidenceAsQuestions),
Response = bug_found(Bug, EvidenceAsQuestions).
%-----------------------------------------------------------------------------%
% Search the search space for a question for the oracle. The search
% should respond with a question about a suspect, or a request for an
% explicit subree to be generated. A new search mode is returned so
% that the search algorithm being used can remember its current state
% next time round.
%
:- pred search(S::in, oracle_state::in,
search_space(T)::in, search_space(T)::out,
search_mode::in, search_mode::in,
search_mode::out, search_response::out) is det <= mercury_edt(S, T).
search(Store, Oracle, !SearchSpace, top_down, FallBackSearchMode,
NewMode, Response) :-
top_down_search(Store, Oracle, !SearchSpace, Response),
% We always go back to the fallback search mode after a top-down
% search, because some fallback searches (such as divide and query)
% use top-down as a fail safe and we want the fallback search to
% resume after the top-down search.
NewMode = FallBackSearchMode.
search(Store, Oracle, !SearchSpace, SearchMode, FallBackSearchMode,
NewMode, Response) :-
SearchMode = follow_subterm_end(SuspectId, ArgPos, TermPath,
LastUnknown, HowTrack),
follow_subterm_end_search(Store, Oracle, !SearchSpace, HowTrack,
LastUnknown, SuspectId, ArgPos, TermPath, FallBackSearchMode,
NewMode, Response).
search(Store, Oracle, !SearchSpace, SearchMode, FallBackSearchMode, NewMode,
Response) :-
SearchMode = binary(PathArray, Top - Bottom, LastTested),
binary_search(Store, Oracle, PathArray, Top, Bottom, LastTested,
!SearchSpace, FallBackSearchMode, NewMode, Response).
search(Store, Oracle, !SearchSpace, divide_and_query(Weighting), _, NewMode,
Response) :-
divide_and_query_search(Store, Oracle, Weighting, !SearchSpace,
Response, NewMode).
:- pred top_down_search(S::in, oracle_state::in,
search_space(T)::in, search_space(T)::out,
search_response::out) is det <= mercury_edt(S, T).
top_down_search(Store, Oracle, !SearchSpace, Response) :-
%
% If there's no root yet (because the oracle hasn't asserted any nodes
% are erroneous yet) then use the topmost suspect as a starting point.
%
( root(!.SearchSpace, RootId) ->
Start = RootId
;
topmost_det(!.SearchSpace, Start)
),
first_unknown_descendent(Store, Oracle, Start, !SearchSpace,
MaybeUnknownDescendent),
(
MaybeUnknownDescendent = found(Unknown),
Response = question(Unknown, top_down)
;
MaybeUnknownDescendent = not_found,
(
choose_skipped_suspect(!.SearchSpace, SkippedSuspect)
->
Response = question(SkippedSuspect, skipped)
;
% Since the are no skipped suspects and no unknown
% suspects in the search space, if there is a root
% (i.e. an erroneous suspect), then it must be a bug.
% Note that only top down search actually checks if a
% bug was found. This is okay, since all the other
% search algorithms call top down search if they can't
% find an unknown suspect.
root(!.SearchSpace, BugId)
->
(
children(Store, Oracle, BugId, !SearchSpace, BugChildren),
non_ignored_descendents(Store, Oracle, BugChildren,
!SearchSpace, NonIgnoredDescendents),
list.filter(suspect_correct_or_inadmissible(!.SearchSpace),
NonIgnoredDescendents, CorrectDescendents, [])
->
list.filter(suspect_inadmissible(!.SearchSpace), BugChildren,
InadmissibleChildren),
Response = found_bug(BugId, CorrectDescendents,
InadmissibleChildren)
;
throw(internal_error("top_down_search",
"bug has unexplored or unknown children"))
)
;
% Try to extend the search space upwards. If this fails
% and we're not at the topmost traced node, then request that
% an explicit supertree be generated.
(
extend_search_space_upwards(Store, Oracle, !.SearchSpace,
ExtendedSearchSpace)
->
top_down_search(Store, Oracle, ExtendedSearchSpace,
!:SearchSpace, Response)
;
topmost_det(!.SearchSpace, TopMostId),
TopMostNode = get_edt_node(!.SearchSpace, TopMostId),
( edt_topmost_node(Store, TopMostNode) ->
% We can't look any higher.
Response = no_suspects
;
Response = require_explicit_supertree
)
)
)
;
MaybeUnknownDescendent = require_explicit_subtree(RequireExplicitId),
Response = require_explicit_subtree(RequireExplicitId)
).
:- pred follow_subterm_end_search(S::in, oracle_state::in,
search_space(T)::in, search_space(T)::out, how_track_subterm::in,
maybe(suspect_id)::in, suspect_id::in,
arg_pos::in, term_path::in, search_mode::in, search_mode::out,
search_response::out) is det <= mercury_edt(S, T).
follow_subterm_end_search(Store, Oracle, !SearchSpace, HowTrack,
LastUnknown, SuspectId, ArgPos, TermPath, FallBackSearchMode,
NewMode, SearchResponse) :-
follow_subterm_end_search_2(Store, Oracle, !SearchSpace, HowTrack,
map.init, _, LastUnknown, SuspectId, ArgPos, TermPath,
FallBackSearchMode, NewMode, SearchResponse).
:- pred follow_subterm_end_search_2(S::in, oracle_state::in,
search_space(T)::in, search_space(T)::out, how_track_subterm::in,
map(proc_layout, unit)::in, map(proc_layout, unit)::out,
maybe(suspect_id)::in, suspect_id::in,
arg_pos::in, term_path::in, search_mode::in, search_mode::out,
search_response::out) is det <= mercury_edt(S, T).
follow_subterm_end_search_2(Store, Oracle, !SearchSpace, HowTrack,
!TriedShortcutProcs, LastUnknown, SuspectId, ArgPos, TermPath,
FallBackSearchMode, NewMode, SearchResponse) :-
find_subterm_origin(Store, Oracle, SuspectId, ArgPos, TermPath, HowTrack,
!TriedShortcutProcs, !SearchSpace, FindOriginResponse),
(
FindOriginResponse = primitive_op(BindingSuspectId, FileName,
LineNo, PrimOpType, Output),
ProcLabel = get_proc_label_for_suspect(Store, !.SearchSpace,
BindingSuspectId),
(
Output = yes,
% BindingSuspectId = SuspectId since the
% subterm is an output of SuspectId.
BindingNode = get_edt_node(!.SearchSpace, SuspectId),
ArgNum = edt_arg_pos_to_user_arg_num(Store, BindingNode, ArgPos),
MaybePath = yes([ArgNum | TermPath])
;
Output = no,
% Since the subterm is not an output of the
% binding node, it will not appear in any of the
% arguments of the binding node (it can't be an
% input, because then it would have been bound outside
% the node).
MaybePath = no
),
(
% We ask about the binding node even if it was
% previously skipped, since this behaviour is
% more predictable from the user's perspective.
%
( suspect_unknown(!.SearchSpace, BindingSuspectId)
; suspect_skipped(!.SearchSpace, BindingSuspectId)
)
->
SearchResponse = question(BindingSuspectId,
binding_node(PrimOpType, FileName, LineNo,
MaybePath, ProcLabel, no)),
NewMode = FallBackSearchMode
;
(
LastUnknown = yes(Unknown),
suspect_still_unknown(!.SearchSpace, Unknown)
->
Reason = binding_node(PrimOpType, FileName, LineNo, MaybePath,
ProcLabel, yes),
SearchResponse = question(Unknown, Reason),
NewMode = FallBackSearchMode
;
search(Store, Oracle, !SearchSpace, FallBackSearchMode,
FallBackSearchMode, NewMode, SearchResponse)
)
)
;
FindOriginResponse = not_found,
(
LastUnknown = yes(Unknown),
suspect_still_unknown(!.SearchSpace, Unknown)
->
SearchResponse = question(Unknown, subterm_no_proc_rep),
NewMode = FallBackSearchMode
;
search(Store, Oracle, !SearchSpace,
FallBackSearchMode, FallBackSearchMode,
NewMode, SearchResponse)
)
;
FindOriginResponse = require_explicit_subtree,
SearchResponse = require_explicit_subtree(SuspectId),
%
% Record the current position of the search so
% we can continue where we left off once the explicit
% subtree has been generated.
%
NewMode = follow_subterm_end(SuspectId, ArgPos, TermPath,
LastUnknown, HowTrack)
;
FindOriginResponse = require_explicit_supertree,
SearchResponse = require_explicit_supertree,
NewMode = follow_subterm_end(SuspectId, ArgPos, TermPath,
LastUnknown, HowTrack)
;
FindOriginResponse = origin(OriginId, OriginArgPos,
OriginTermPath, SubtermMode),
(
suspect_unknown(!.SearchSpace, OriginId)
->
NewLastUnknown = yes(OriginId)
;
NewLastUnknown = LastUnknown
),
(
%
% Check if it's worth continuing tracking the sub-term.
% We want to stop if we enter a portion of the search
% space known not to contain the bug from which we
% can't return (for example if we come across an
% erroneous node where the sub-term is an input).
%
give_up_subterm_tracking(!.SearchSpace, OriginId, SubtermMode)
->
(
LastUnknown = yes(Unknown),
suspect_still_unknown(!.SearchSpace, Unknown)
->
SearchResponse = question(Unknown, binding_node_eliminated),
NewMode = FallBackSearchMode
;
search(Store, Oracle, !SearchSpace,
FallBackSearchMode, FallBackSearchMode,
NewMode, SearchResponse)
)
;
%
% This recursive call will not lead to an infinite loop
% because eventually either the sub-term will be bound
% (and find_subterm_origin will respond with
% primitive_op/3) or there will be insufficient tracing
% information to continue (and find_subterm_origin will
% respond with not_found).
%
follow_subterm_end_search_2(Store, Oracle, !SearchSpace, HowTrack,
!TriedShortcutProcs, NewLastUnknown, OriginId,
OriginArgPos, OriginTermPath,
FallBackSearchMode, NewMode, SearchResponse)
)
).
% setup_binary_search(SearchSpace, SuspectId, SearchMode).
% Sets up the search mode to do a binary search between SuspectId
% and either the root of the search space if a suspect has
% previously been marked erroneous, or the topmost node if no suspect
% has yet been marked erroneous.
%
:- pred setup_binary_search(search_space(T)::in, suspect_id::in,
search_mode::out) is det.
setup_binary_search(SearchSpace, SuspectId, SearchMode) :-
( root(SearchSpace, RootId) ->
TopId = RootId,
BottomId = SuspectId
;
topmost_det(SearchSpace, TopId),
BottomId = SuspectId
),
( get_path(SearchSpace, BottomId, TopId, Path) ->
PathArray = array.from_list(Path),
array.bounds(PathArray, Top, Bottom),
SearchMode = binary(PathArray, Top - Bottom, Bottom)
;
throw(internal_error("setup_binary_search",
"TopId not an ancestor of BottomId"))
).
:- pred binary_search(S::in, oracle_state::in,
array(suspect_id)::in, int::in, int::in, int::in,
search_space(T)::in, search_space(T)::out, search_mode::in,
search_mode::out, search_response::out) is det <= mercury_edt(S, T).
binary_search(Store, Oracle, PathArray, Top, Bottom, LastTested,
!SearchSpace, FallBackSearchMode, NewMode, Response) :-
SuspectId = PathArray ^ elem(LastTested),
%
% Check what the result of the query about LastTested was and adjust
% the range appropriately.
%
(
% The oracle answered `erroneous'.
suspect_in_excluded_complement(!.SearchSpace, SuspectId)
->
NewTop = LastTested + 1,
NewBottom = Bottom
;
% The oracle answered `correct' or `inadmissible'
suspect_in_excluded_subtree(!.SearchSpace, SuspectId)
->
NewTop = Top,
NewBottom = LastTested - 1
;
% The suspect is trusted(ignored) or was skipped.
NewTop = Top,
NewBottom = Bottom
),
(
NewTop > NewBottom
->
% Revert to the fallback search mode when binary search is
% over.
search(Store, Oracle, !SearchSpace,
FallBackSearchMode, FallBackSearchMode, NewMode, Response)
;
(
find_unknown_closest_to_middle(!.SearchSpace, PathArray,
NewTop, NewBottom, UnknownClosestToMiddle)
->
NewMode = binary(PathArray, NewTop - NewBottom,
UnknownClosestToMiddle),
Response = question(PathArray ^ elem(UnknownClosestToMiddle),
binary(NewBottom, NewTop, UnknownClosestToMiddle))
;
% No unknown suspects on the path, so revert to
% the fallback search mode.
search(Store, Oracle, !SearchSpace,
FallBackSearchMode, FallBackSearchMode, NewMode, Response)
)
).
% find_unknown_closest_to_middle(SearchSpace, PathArray, Top, Bottom,
% Unknown):
%
% Unknown is the position in PathArray of the suspect which has status
% unknown and is closest to halfway between From and To which are
% also indexes into PathArray. Fails if there are no unknown suspects
% between From and To (inclusive).
%
:- pred find_unknown_closest_to_middle(search_space(T)::in,
array(suspect_id)::in, int::in, int::in, int::out) is semidet.
find_unknown_closest_to_middle(SearchSpace, PathArray, Top, Bottom, Unknown) :-
Middle = Top + ((Bottom - Top) // 2),
find_unknown_closest_to_range(SearchSpace, PathArray, Top, Bottom,
Middle, Middle, Unknown).
% find_unknown_closest_to_range(SearchSpace, PathArray, OuterTop,
% OuterBottom, InnerTop, InnerBottom, Unknown):
%
% Unknown is a position in PathArray between OuterTop and OuterBottom
% (inclusive) where the status of the suspect is unknown. The preferred
% position to return is as close as possible to InnerTop and
% InnerBottom, with the proviso that elements between InnerTop and
% InnerBottom (exclusive) aren't tested, since the caller has already
% found they were not unknown.
%
:- pred find_unknown_closest_to_range(search_space(T)::in,
array(suspect_id)::in, int::in, int::in, int::in, int::in, int::out)
is semidet.
find_unknown_closest_to_range(SearchSpace, PathArray, OuterTop, OuterBottom,
InnerTop, InnerBottom, Unknown) :-
InnerTop =< InnerBottom,
( OuterTop =< InnerTop ; InnerBottom =< OuterBottom ),
(
OuterTop =< InnerTop,
suspect_unknown(SearchSpace, PathArray ^ elem(InnerTop))
->
Unknown = InnerTop
;
InnerBottom =< OuterBottom,
suspect_unknown(SearchSpace, PathArray ^ elem(InnerBottom))
->
Unknown = InnerBottom
;
find_unknown_closest_to_range(SearchSpace, PathArray,
OuterTop, OuterBottom, InnerTop - 1, InnerBottom + 1, Unknown)
).
:- pred divide_and_query_search(S::in, oracle_state::in,
weighting_heuristic::in,
search_space(T)::in, search_space(T)::out, search_response::out,
search_mode::out) is det <= mercury_edt(S, T).
divide_and_query_search(Store, Oracle, Weighting, !SearchSpace,
Response, divide_and_query(Weighting)) :-
% If there's no root yet (because the oracle hasn't asserted any nodes
% are erroneous yet), then use top-down search.
( root(!.SearchSpace, RootId) ->
( children(Store, Oracle, RootId, !SearchSpace, Children) ->
find_middle_weight(Store, Oracle, Weighting, Children,
RootId, no, !SearchSpace, Response)
;
Response = require_explicit_subtree(RootId)
)
;
top_down_search(Store, Oracle, !SearchSpace, Response)
).
% Call find_middle_weight if we are able to find the children of the
% given suspect id, otherwise return a require_explicit_subtree
% search response in the last argument.
%
:- pred find_middle_weight_if_children(S::in,
oracle_state::in, weighting_heuristic::in, suspect_id::in,
suspect_id::in, maybe(suspect_id)::in,
search_space(T)::in, search_space(T)::out, search_response::out)
is det <= mercury_edt(S, T).
find_middle_weight_if_children(Store, Oracle, Weighting, SuspectId, TopId,
MaybeLastUnknown, !SearchSpace, Response) :-
( children(Store, Oracle, SuspectId, !SearchSpace, Children) ->
find_middle_weight(Store, Oracle, Weighting, Children, TopId,
MaybeLastUnknown, !SearchSpace, Response)
;
Response = require_explicit_subtree(SuspectId)
).
% find_middle_weight(Store, Oracle, Weighting, SuspectIds,
% TopId, MaybeLastUnknown, !SearchSpace, Response).
% Find the unknown suspect whose weight is closest to half the weight
% of TopId, considering only the heaviest suspect in SuspectIds, the
% heaviest child of the heaviest suspect in SuspectIds and so on.
% MaybeLastUnknown is the last node that was unknown in the search (if
% any).
%
:- pred find_middle_weight(S::in, oracle_state::in,
weighting_heuristic::in, list(suspect_id)::in, suspect_id::in,
maybe(suspect_id)::in,
search_space(T)::in, search_space(T)::out, search_response::out)
is det <= mercury_edt(S, T).
find_middle_weight(Store, Oracle, Weighting, [], TopId,
MaybeLastUnknown, !SearchSpace, Response) :-
(
MaybeLastUnknown = yes(LastUnknown),
suspect_still_unknown(!.SearchSpace, LastUnknown)
->
Response = question(LastUnknown, divide_and_query(Weighting,
get_weight(!.SearchSpace, TopId),
get_weight(!.SearchSpace, LastUnknown)))
;
% This could happen when there were no unknown suspects
% encountered during the search, in which case we revert
% to top-down search.
top_down_search(Store, Oracle, !SearchSpace, Response)
).
find_middle_weight(Store, Oracle, Weighting, [SuspectId | SuspectIds], TopId,
MaybeLastUnknown, !SearchSpace, Response) :-
TopWeight = get_weight(!.SearchSpace, TopId),
Target = TopWeight // 2,
%
% Find the heaviest suspect:
%
Weight = get_weight(!.SearchSpace, SuspectId),
list.foldl2(max_weight(!.SearchSpace), SuspectIds,
Weight, MaxWeight, SuspectId, Heaviest),
( MaxWeight > Target ->
( suspect_unknown(!.SearchSpace, Heaviest) ->
NewMaybeLastUnknown = yes(Heaviest)
;
NewMaybeLastUnknown = MaybeLastUnknown
),
find_middle_weight_if_children(Store, Oracle, Weighting, Heaviest,
TopId, NewMaybeLastUnknown, !SearchSpace, Response)
;
( suspect_unknown(!.SearchSpace, Heaviest) ->
(
MaybeLastUnknown = yes(LastUnknown),
suspect_still_unknown(!.SearchSpace, LastUnknown)
->
LastUnknownWeight = get_weight(!.SearchSpace, LastUnknown),
%
% If the last unknown suspect was closer to
% the target weight then ask about it.
%
( LastUnknownWeight - Target < Target - MaxWeight ->
Response = question(LastUnknown,
divide_and_query(Weighting, TopWeight,
LastUnknownWeight))
;
Response = question(Heaviest,
divide_and_query(Weighting, TopWeight, MaxWeight))
)
;
Response = question(Heaviest,
divide_and_query(Weighting, TopWeight, MaxWeight))
)
;
(
MaybeLastUnknown = yes(LastUnknown),
suspect_still_unknown(!.SearchSpace, LastUnknown)
->
LastUnknownWeight = get_weight(!.SearchSpace, LastUnknown),
Response = question(LastUnknown,
divide_and_query(Weighting, TopWeight, LastUnknownWeight))
;
% Look deeper until we find an unknown:
find_middle_weight_if_children(Store, Oracle, Weighting,
Heaviest, TopId, no, !SearchSpace, Response)
)
)
).
:- pred max_weight(search_space(T)::in, suspect_id::in,
int::in, int::out, suspect_id::in, suspect_id::out) is det.
max_weight(SearchSpace, SuspectId, PrevMax, NewMax,
PrevSuspectId, NewSuspectId) :-
Weight = get_weight(SearchSpace, SuspectId),
( Weight > PrevMax ->
NewMax = Weight,
NewSuspectId = SuspectId
;
NewMax = PrevMax,
NewSuspectId = PrevSuspectId
).
%-----------------------------------------------------------------------------%
% Check that a suspect is still unknown. This is called by the search
% algorithms to make double sure that a suspect is still unknown (it
% might not be unknown if, for example, an erroneous suspect was added
% to the search space during the search).
%
:- pred suspect_still_unknown(search_space(T)::in, suspect_id::in) is semidet.
suspect_still_unknown(SearchSpace, SuspectId) :-
suspect_unknown(SearchSpace, SuspectId).
%-----------------------------------------------------------------------------%
reason_to_string(start) = "this is the node where the `dd' command "
++ "was issued.".
reason_to_string(binding_node(PrimOpType, FileName, LineNo,
MaybePath, ProcLabel, Eliminated)) = Str :-
PrimOpStr = primitive_op_type_to_string(PrimOpType),
LineNoStr = int_to_string(LineNo),
get_pred_attributes(ProcLabel, SymModule, Name, Arity, PredOrFunc),
(
PredOrFunc = function,
PredOrFuncStr = "function"
;
PredOrFunc = predicate,
PredOrFuncStr = "predicate"
),
Module = sym_name_to_string(SymModule),
ArityStr = int_to_string(Arity),
(
Eliminated = yes,
EliminatedSent = " That node was, however, previously "
++ "eliminated from the bug search."
;
Eliminated = no,
EliminatedSent = ""
),
(
MaybePath = yes(Path),
PathStrings = list.map(int_to_string, Path),
PathStr = string.join_list("/", PathStrings),
PathSent = "The path to the subterm in the atom is " ++ PathStr ++ "."
;
MaybePath = no,
PathSent = ""
),
Str = "the marked subterm was bound by the " ++
PrimOpStr ++ " inside the " ++ PredOrFuncStr ++
" " ++ Module ++ "." ++ Name ++ "/" ++ ArityStr ++
" (" ++ FileName ++ ":" ++ LineNoStr ++ "). " ++
PathSent ++ EliminatedSent.
reason_to_string(top_down) =
"this is the next node in the top-down search.".
reason_to_string(subterm_no_proc_rep) =
"tracking of the marked subterm had to be aborted here, because of "
++ "missing tracing information.".
reason_to_string(binding_node_eliminated) =
"tracking of the marked subterm was stopped here, because the binding "
++ "node lies in a portion of the tree which has been eliminated.".
reason_to_string(binary(Bottom, Top, Split)) = Str :-
PathLengthStr = int_to_string_thousands(Bottom - Top + 1),
SubPath1LengthStr = int_to_string_thousands(Bottom - Split),
SubPath2LengthStr = int_to_string_thousands(Split - Top + 1),
Str = "this node divides a path of length " ++ PathLengthStr
++ " into two paths of length " ++
SubPath1LengthStr ++ " and " ++ SubPath2LengthStr ++ ".".
reason_to_string(divide_and_query(Weighting, OldWeight, SubtreeWeight)) =
weighting_to_reason_string(Weighting, OldWeight - SubtreeWeight,
SubtreeWeight).
reason_to_string(skipped) =
"there are no more non-skipped questions left.".
reason_to_string(revise) = "this question is being revisited, because of "
++ "an unsuccessful previous bug search.".
:- func weighting_to_reason_string(weighting_heuristic, int, int) = string.
weighting_to_reason_string(number_of_events, Weight1, Weight2) = Str :-
Weight1Str = int_to_string_thousands(Weight1),
Weight2Str = int_to_string_thousands(Weight2),
Str = "this node divides the suspect area into two regions of "
++ Weight1Str ++ " and " ++ Weight2Str ++ " events each.".
weighting_to_reason_string(suspicion, Weight1, Weight2) = Str :-
Weight1Str = int_to_string_thousands(Weight1),
Weight2Str = int_to_string_thousands(Weight2),
Str = "this node divides the suspect area into " ++
"two regions of suspicion " ++ Weight1Str ++ " and
" ++ Weight2Str ++ ".".
show_info(Store, OutStream, Analyser, !IO) :-
SearchSpace = Analyser ^ search_space,
some [!FieldNames, !Data] (
!:FieldNames = [],
!:Data = [],
%
% Get the context of the current question.
%
(
Analyser ^ last_search_question =
yes(suspect_and_reason(LastId, Reason)),
(
edt_context(Store, get_edt_node(SearchSpace,
LastId), FileName - LineNo, MaybeReturnContext)
->
(
MaybeReturnContext = yes(ReturnFileName - ReturnLineNo),
ContextStr = FileName ++ ":" ++ int_to_string(LineNo)
++ " (" ++ ReturnFileName ++ ":"
++ int_to_string(ReturnLineNo) ++ ")"
;
MaybeReturnContext = no,
ContextStr = FileName ++ ":" ++ int_to_string(LineNo)
),
list.append(!.FieldNames, ["Context of current question"],
!:FieldNames),
list.append(!.Data, [ContextStr], !:Data)
;
true
)
;
Analyser ^ last_search_question = no,
throw(internal_error("show_info", "no last question"))
),
list.append(!.FieldNames, ["Search mode"],
!:FieldNames),
list.append(!.Data, [search_mode_to_string(
Analyser ^ search_mode)], !:Data),
MaybeWeighting = get_current_maybe_weighting(SearchSpace),
( MaybeWeighting = yes(number_of_events) ->
( root(SearchSpace, RootId) ->
StartId = RootId
;
topmost_det(SearchSpace, StartId)
),
Weight = get_weight(SearchSpace, StartId),
( Analyser ^ search_mode = divide_and_query(number_of_events) ->
list.append(!.FieldNames, ["Estimated questions remaining"],
!:FieldNames),
EstimatedQuestions = float.ceiling_to_int(
math.log2(float(Weight))),
list.append(!.Data, [int_to_string(EstimatedQuestions)],
!:Data)
;
true
),
list.append(!.FieldNames, ["Number of suspect events"],
!:FieldNames),
list.append(!.Data, [int_to_string_thousands(Weight)], !:Data)
;
true
),
InfoMessage = string.format_table([left(!.FieldNames), left(!.Data)],
" : ")
),
ReasonStr = reason_to_string(Reason),
ReasonSent = "The current question was chosen because " ++ ReasonStr,
WrappedReason = string.word_wrap(ReasonSent, 72),
io.format(OutStream, "%s\n%s\n", [s(InfoMessage), s(WrappedReason)], !IO).
:- func search_mode_to_string(search_mode) = string.
search_mode_to_string(top_down) = "top down".
search_mode_to_string(follow_subterm_end(_, _, _, _, track_accurate)) =
"tracking marked sub-term (using accurate algorithm)".
search_mode_to_string(follow_subterm_end(_, _, _, _, track_fast)) =
"tracking marked sub-term (using fast algorithm)".
search_mode_to_string(binary(_, _, _)) = "binary search on path".
search_mode_to_string(divide_and_query(number_of_events)) =
"divide and query".
search_mode_to_string(divide_and_query(suspicion)) =
"suspicion divide and query".