Class: BudMeta

Inherits:
Object
  • Object
show all
Defined in:
lib/bud/bud_meta.rb

Overview

:nodoc: all

Defined Under Namespace

Classes: Edge, Node

Instance Method Summary collapse

Constructor Details

#initialize(bud_i) ⇒ BudMeta

Returns a new instance of BudMeta.



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# File 'lib/bud/bud_meta.rb', line 4

def initialize(bud_i)
  @bud_instance = bud_i
  @declarations = bud_i.methods.select {|m| m =~ /^__bloom__.+$/}.map {|m| m.to_s}
  @rule_idx = 0

  # The results of bud_meta are analyzed further using a helper Bloom
  # instance. See depanalysis().
  @dependency_analysis = nil
end

Instance Method Details

#analyze_dependencies(nodes) ⇒ Object

nodes = name => node



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# File 'lib/bud/bud_meta.rb', line 259

def analyze_dependencies(nodes)  # nodes = {node name => node}
  preds_in_lhs = nodes.select {|_, node| node.in_lhs}.map {|name, _| name}.to_set
  preds_in_body = nodes.select {|_, node| node.in_body}.map {|name, _| name}.to_set

  bud = @bud_instance
  out = bud.options[:stdout]
  out ||= $stdout
  bud.t_provides.each do |p|
    pred, input = p.interface, p.input
    if input
      unless preds_in_body.include? pred
        # input interface is underspecified if not used in any rule body
        bud.t_underspecified << [pred, true] # true indicates input mode
        out.puts "Warning: input interface #{pred} not used"
      end
    else
      unless preds_in_lhs.include? pred
        # output interface underspecified if not in any rule's lhs
        bud.t_underspecified << [pred, false]  # false indicates output mode
        out.puts "Warning: output interface #{pred} not used"
      end
    end
  end
end

#calc_stratum(node, neg, temporal, path) ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 241

def calc_stratum(node, neg, temporal, path)
  if node.status == :in_process
    if neg and not temporal and not node.already_neg
      raise Bud::CompileError, "unstratifiable program: #{path.uniq.join(',')}"
    end
  elsif node.status == :init
    node.status = :in_process
    node.edges.each do |edge|
      next unless edge.op == "<="
      node.already_neg = neg
      body_stratum = calc_stratum(edge.to, (neg or edge.neg), (edge.temporal or temporal), path + [edge.to.name])
      node.stratum = [node.stratum, body_stratum + (edge.neg ? 1 : 0)].max
    end
    node.status = :done
  end
  node.stratum
end

#check_rule_ast(pt) ⇒ Object

Perform some basic sanity checks on the AST of a rule block. We expect a rule block to consist of a :defn whose body consists of a sequence of statements. Each statement is a :call node. Returns nil (no error found), a Sexp (containing an error), or a pair of [Sexp, error message].



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# File 'lib/bud/bud_meta.rb', line 157

def check_rule_ast(pt)
  # :defn format: node tag, block name, args, body_0, ..., body_n
  tag, name, args, *body = pt
  return pt if tag != :defn

  body.each_with_index do |n,i|
    next if i == 0 and n == s(:nil) # a block got rewritten to an empty block

    # Check for a common case
    if n.sexp_type == :lasgn
      return [n, "illegal operator: '='"]
    end
    return pt unless n.sexp_type == :call and n.length == 4

    # Rule format: call tag, lhs, op, rhs
    _, lhs, op, rhs = n

    # Check that LHS references a named collection
    lhs_name = get_qual_name(lhs)
    return [n, "unexpected lhs format: #{lhs}"] if lhs_name.nil?
    unless @bud_instance.tables.has_key? lhs_name.to_sym or
           @bud_instance.lattices.has_key? lhs_name.to_sym
      return [n, "Collection does not exist: '#{lhs_name}'"]
    end

    return [n, "illegal operator: '#{op}'"] unless [:<, :<=].include? op

    # Check superator invocation. A superator that begins with "<" is parsed
    # as a call to the binary :< operator. The right operand to :< is a :call
    # node; the LHS of the :call is the actual rule body, the :call's oper is
    # the rest of the superator (unary ~, -, +), and the RHS is empty.  Note
    # that ParseTree encodes unary "-" and "+" as :-@ and :-+, respectively.
    # XXX: We don't check for illegal superators (e.g., "<--"). That would be
    # tricky, because they are encoded as a nested unary op in the rule body.
    if op == :<
      return n unless rhs.sexp_type == :call
      op_tail = rhs[2]
      return n unless [:~, :-@, :+@].include? op_tail
      rhs_args = rhs[3..-1]
      return n unless rhs_args.empty?
    end
  end

  return nil # No errors found
end

#compute_node_graph ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 208

def compute_node_graph
  nodes = {}
  @bud_instance.toplevel.t_depends.each do |d|
    # t_depends [:bud_instance, :rule_id, :lhs, :op, :body] => [:nm, :in_body]
    lhs = (nodes[d.lhs] ||= Node.new(d.lhs, :init, 0, [], true, false))
    lhs.in_lhs = true
    body = (nodes[d.body] ||= Node.new(d.body, :init, 0, [], false, true))
    body.in_body = true
    temporal = (d.op != "<=")
    lhs.edges << Edge.new(body, d.op, d.nm, temporal)
  end

  return nodes
end

#depanalysis ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 284

def depanalysis
  if @dependency_analysis.nil?
    require 'bud/depanalysis'
    da = ::DepAnalysis.new
    da.providing <+ @bud_instance.tables[:t_provides].to_a
    da.depends <+ @bud_instance.t_depends.map{|d| [d.lhs, d.op, d.body, d.nm]}
    da.tick_internal
    @dependency_analysis = da
  end
  @dependency_analysis
end

#dump_rewrite(strata) ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 296

def dump_rewrite(strata)
  fout = File.new("#{@bud_instance.class}_rewritten.txt", "w")
  fout.puts "Declarations:"

  strata.each_with_index do |rules, i|
    fout.puts "================================="
    fout.puts "Stratum #{i}"
    rules.each do |r|
      fout.puts "#{r.bud_obj.class}##{r.bud_obj.object_id} #{r.rule_id}"
      fout.puts "\tsrc:      #{r.src}"
      fout.puts "\torig src: #{r.orig_src}"
    end
  end
  fout.close
end

#find_body_rels(rule) ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 69

def find_body_rels(rule)
  @bud_instance.t_depends.map do |d|
    [d.body, d.nm] if d.rule_id == rule.rule_id and d.bud_obj == rule.bud_obj
  end.compact
end

#get_qual_name(pt) ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 136

def get_qual_name(pt)
  # expect to see a parse tree corresponding to a dotted name
  #    a.b.c == s(:call, s1,  :c)
  # where s1 == s(:call, s2,  :b)
  # where s2 == s(:call, nil, :a)
  tag, recv, name, *args = pt
  return nil unless tag == :call and args.empty?

  if recv
    qn = get_qual_name(recv)
    return nil if qn.nil? or qn.size == 0
    return "#{qn}.#{name}"
  else
    return name.to_s
  end
end

#meta_rewrite ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 14

def meta_rewrite
  shred_rules # capture dependencies, rewrite rules

  stratified_rules = []
  if @bud_instance.toplevel == @bud_instance
    nodes = compute_node_graph
    analyze_dependencies(nodes)

    stratum_map = stratify_preds(nodes)
    top_stratum = stratum_map.values.max
    top_stratum ||= -1

    # stratum_map = {fully qualified pred => stratum}. Copy stratum_map data
    # into t_stratum format.
    raise unless @bud_instance.t_stratum.to_a.empty?
    @bud_instance.t_stratum.merge(stratum_map.to_a)

    stratified_rules = Array.new(top_stratum + 2) { [] }  # stratum -> [ rules ]
    @bud_instance.t_rules.each do |rule|
      if rule.op == '<='
        # Deductive rules are assigned to strata based on the basic Datalog
        # stratification algorithm. Note that we don't place all the rules
        # with a given lhs relation in the same strata; rather, we place a
        # rule in the lowest strata we can, as determined by the rule's rhs
        # relations (and whether the rel is used in a non-monotonic context).
        body_rels = find_body_rels(rule)
        body_strata = body_rels.map {|r,is_nm| stratum_map[r] + (is_nm ? 1 : 0) || 0}
        belongs_in = body_strata.max

        # If the rule body doesn't reference any collections, it won't be
        # assigned a stratum, so just place it in stratum zero
        belongs_in ||= 0
        stratified_rules[belongs_in] << rule
      else
        # All temporal rules are placed in the last stratum
        stratified_rules[top_stratum + 1] << rule
      end
    end

    # stratified_rules[0] may be empty if none of the nodes at stratum 0 are
    # on the lhs stratified_rules[top_stratum+1] will be empty if there are no
    # temporal rules.
    stratified_rules.reject! {|r| r.empty?}

    stratified_rules.each_with_index do |strat,strat_num|
      strat.each do |rule|
        @bud_instance.t_rule_stratum << [rule.bud_obj, rule.rule_id, strat_num]
      end
    end

    dump_rewrite(stratified_rules) if @bud_instance.options[:dump_rewrite]
  end
  return stratified_rules
end

#rewrite_rule_block(klass, block_name) ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 95

def rewrite_rule_block(klass, block_name)
  return unless klass.respond_to? :__bloom_asts__

  pt = klass.__bloom_asts__[block_name]
  return if pt.nil?

  pt = Marshal.load(Marshal.dump(pt)) # deep copy because RuleRewriter mucks up pt
  if @bud_instance.options[:dump_ast]
    require 'pp'
    pp pt
  end
  tmp_expander = TempExpander.new
  pt = tmp_expander.process(pt)
  tmp_expander.tmp_tables.each do |t|
    @bud_instance.temp(t.to_sym)
  end

  rv = check_rule_ast(pt)
  unless rv.nil?
    if rv.class <= Sexp
      error_pt = rv
      error_msg = "parse error"
    else
      error_pt, error_msg = rv
    end

    # try to dump the source code associated with the problematic block, so as
    # to produce a more meaningful error message.
    begin
      code = Ruby2Ruby.new.process(Marshal.load(Marshal.dump(error_pt)))
      src_msg = "\nCode: #{code}"
    rescue Exception
      src_msg = ""
    end
    raise Bud::CompileError, "#{error_msg} in rule block \"#{block_name}\"#{src_msg}"
  end
  rewriter = RuleRewriter.new(@bud_instance, @rule_idx)
  rewriter.process(pt)
  return rewriter
end

#shred_rules ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 75

def shred_rules
  # After making this pass, we no longer care about the names of methods.  We
  # are shredding down to the granularity of rule heads.
  rulebag = {}
  @bud_instance.class.ancestors.reverse.each do |anc|
    @declarations.each do |meth_name|
      rw = rewrite_rule_block(anc, meth_name)
      if rw
        rulebag[meth_name] = rw
        @rule_idx = rw.rule_idx
      end
    end
  end

  rulebag.each_value do |v|
    v.rules.each {|r| @bud_instance.t_rules << r}
    v.depends.each {|d| @bud_instance.t_depends << d}
  end
end

#stratify_preds(nodes) ⇒ Object 



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# File 'lib/bud/bud_meta.rb', line 223

def stratify_preds(nodes)
  nodes.each_value {|n| calc_stratum(n, false, false, [n.name])}

  # Normalize stratum numbers because they may not be 0-based or consecutive
  remap = {}
  # if the nodes stratum numbers are [2, 3, 2, 4], remap = {2 => 0, 3 => 1, 4 => 2}
  nodes.values.map {|n| n.stratum}.uniq.sort.each_with_index do |num, i|
    remap[num] = i
  end

  stratum_map = {}
  nodes.each_pair do |name, n|
    n.stratum = remap[n.stratum]
    stratum_map[n.name] = n.stratum
  end
  return stratum_map
end