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Improve alternative selection.

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* new/targets.jam
  (main-target.select-alternative): Rewrite.
  (main-target.generate-really): Issue error in all cases where best
  alternative could not be found.
  (basic-target.match): Renamed from 'match-rank' and changed.

* boost_build_v2.html: Document new algorithm.

* test/alternatives.py: More tests.


[SVN r20331]
This commit is contained in:
Vladimir Prus
2003-10-10 12:14:59 +00:00
parent 914fcb5194
commit 503da68bc4
3 changed files with 156 additions and 71 deletions
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110
src/build/targets.jam
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@@ -366,26 +366,65 @@ class main-target : abstract-target
self.alternatives += $(target) ;
}
# Returns the best viable alternative for this property-set
# See the documentation for selection rules.
local rule select-alternatives ( property-set )
{
local viable ; # alternatives that may be used
local ranks ; # ranks for viable alternatives
for local v in $(self.alternatives)
# The algorithm: we keep the current best viable alternative.
# When we've got new best viable alternative, we compare it
# with the current one.
local best ;
local best-properties ;
if $(self.alternatives[2-])
{
# For now, alternative should be derived from 'basic-target'.
# We'll see if this restriction if reasonable.
assert.equal [ is-a $(v) : basic-target ] : true ;
local m = [ $(v).match-rank $(property-set) ] ;
if $(m)
local bad ;
local worklist = $(self.alternatives) ;
while $(worklist) && ! $(bad)
{
viable += $(v) ;
ranks += $(m) ;
local v = $(worklist[1]) ;
local properties = [ $(v).match $(property-set) ] ;
if $(properties) != no-match
{
if ! $(best)
{
best = $(v) ;
best-properties = $(properties) ;
}
else
{
if $(properties) = $(best-properties)
{
bad = true ;
}
else if $(properties) in $(best-properties)
{
# Do nothing, this alternative is worse
}
else if $(best-properties) in $(properties)
{
best = $(v) ;
best-properties = $(properties) ;
}
else
{
bad = true ;
}
}
}
worklist = $(worklist[2-]) ;
}
if ! $(bad)
{
return $(best) ;
}
}
local best = [ sequence.select-highest-ranked $(viable) : $(ranks) ] ;
return $(best) ;
else
{
return $(self.alternatives) ;
}
}
@@ -486,20 +525,13 @@ class main-target : abstract-target
local best-alternatives = [ select-alternatives $(property-set) ] ;
if ! $(best-alternatives)
{
# TODO: probably, should explain, for each alternative,
# why it can't be build.
print.wrapped-text
"warning: skipped build of" [ full-name ]
errors.error
"skipped build of" [ full-name ]
"with properties" [ $(property-set).raw ]
"because no best-matching alternative could be found"
;
return [ property-set.empty ] ;
}
else if $(best-alternatives[2])
{
# TODO: again, a better error message in in order.
errors.error "Ambiguous alternatives for main target" [ full-name ] ;
}
else
{
local result = [ $(best-alternatives).generate $(property-set) ] ;
@@ -781,32 +813,20 @@ class basic-target : abstract-target
return $(self.default-build) ;
}
# Returns a number which estimates this targets's suitability for
# building with the given 'property-set'. Among several alternatives
# for a main target, the one with greatest match-rank will be used
# to do actual generation. Return of empty value mean this target
# can't be built with the given 'property-set'.
rule match-rank ( property-set )
# Returns the alternative condition for this alternative, if
# the condition is satisfied by 'property-set'.
rule match ( property-set )
{
# First check if our requirements can be satisfied.
local rproperties = [ $(property-set).refine $(self.requirements) ] ;
# Kluge: previously, link-incompatible alternatives were skipped
# completely. Until a better alternative selection algorithm is
# in place, treat such alternatives as having rank of zero.
# As another kluge, add 1 to all other ranks so that zero is worse that
# anything.
if [ $(rproperties).link-incompatible-with $(property-set) ]
local condition = [ $(self.requirements).base ] ;
# Weed out conditional properties.
condition = [ MATCH ^([^:]*)\$ : $(condition) ] ;
if $(condition) in [ $(property-set).raw ]
{
return 0 ;
return $(condition) ;
}
else
{
# Returns the number of properties common to requirements
# and build request.
return [ sequence.length "fake" [ set.intersection
[ $(self.requirements).base ] :
[ $(property-set).raw ] ] ] ;
{
return no-match ;
}
}