Class: Util::CompressedRowStorage

Inherits:
Object
  • Object
show all
Defined in:
lib/ruby-cbc/utils/compressed_row_storage.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#col_idx ⇒ Object

Returns the value of attribute col_idx.



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 4

def col_idx
  @col_idx
end

#model ⇒ Object

Returns the value of attribute model.



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 4

def model
  @model
end

#row_ptr ⇒ Object

Returns the value of attribute row_ptr.



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 4

def row_ptr
  @row_ptr
end

#values ⇒ Object

Returns the value of attribute values.



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 4

def values
  @values
end

#variable_index ⇒ Object

Returns the value of attribute variable_index.



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 4

def variable_index
  @variable_index
end

Class Method Details

.from_model(model) ⇒ Object 



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 6

def self.from_model(model)
  new.tap do |crs|
    crs.model = model
    crs.variable_index = {}
    idx = 0
    while idx < model.vars.size do
      v = model.vars[idx]
      crs.variable_index[v] = idx
      idx += 1
    end
    crs.fill_matrix
  end
end

Instance Method Details

#delete_missing_vars ⇒ Object 



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 64

def delete_missing_vars
  at_least_one_missing = false
  here = present_var_indices
  new_idx = Array.new(@variable_index.count, -1)
  idx = 0
  current_index = 0
  while idx < new_idx.size do
    if here[idx]
      new_idx[idx] = current_index
      current_index += 1
    else
      at_least_one_missing = true
    end
    idx += 1
  end

  return unless at_least_one_missing

  new_variable_index = {}
  @variable_index.each do |v, i|
    new_variable_index[v] = new_idx[i] if new_idx[i] != -1
  end
  @variable_index = new_variable_index
  @col_idx.map! { |idx| new_idx[idx] }
  @model.vars = Array.new(@variable_index.size)
  @variable_index.each do |var, idx|
    @model.vars[idx] = var
  end
end

#fill_matrix ⇒ Object 



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 24

def fill_matrix
  nb_values = model.constraints.map { |c| c.terms.count }.inject(:+) || 0
  @row_ptr = Array.new(model.constraints.count)
  @col_idx = Array.new(nb_values)
  @values = Array.new(nb_values)

  nb_cols = 0
  c_idx = 0
  while c_idx < @model.constraints.size do
    constraint = @model.constraints[c_idx]
    @row_ptr[c_idx] = nb_cols
    nb_insert = constraint.terms.count
    @col_idx[nb_cols, nb_insert] = constraint.terms.map { |term| variable_index[term.var] }
    @values[nb_cols, nb_insert] = constraint.terms.map { |term| term.mult }
    nb_cols += nb_insert
    c_idx += 1
  end
  @row_ptr << @col_idx.count
end

#move_block_to_start(array, block_start_idx, nb_values) ⇒ Object 



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 114

def move_block_to_start(array, block_start_idx, nb_values)
  to_move = array[block_start_idx, nb_values]
  array[nb_values, block_start_idx] = array[0, block_start_idx]
  array[0, nb_values] = to_move
end

#move_constraint_to_start(range_idxs) ⇒ Object 



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 94

def move_constraint_to_start(range_idxs)
  # Move in the model
  constraints = model.constraints[range_idxs]
  @model.constraints = @model.constraints.clone
  @model.constraints[constraints.count, range_idxs.max] = model.constraints[0, range_idxs.min]
  @model.constraints[0, constraints.count] = constraints

  # Move in the matrix
  constraint_start_idx = @row_ptr[range_idxs.min]
  nb_vars = @row_ptr[range_idxs.max + 1] - constraint_start_idx
  offset= @row_ptr[range_idxs.min]
  new_begin = @row_ptr[range_idxs].map! { |idx| idx - offset }
  ((range_idxs.count)..(range_idxs.max)).reverse_each do |idx|
    @row_ptr[idx] = @row_ptr[idx - range_idxs.count] + nb_vars
  end
  @row_ptr[0, range_idxs.count] = new_begin
  move_block_to_start(@col_idx, constraint_start_idx, nb_vars)
  move_block_to_start(@values, constraint_start_idx, nb_vars)
end

#nb_constraints ⇒ Object 



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 20

def nb_constraints
  row_ptr.count - 1
end

#present_var_indices ⇒ Object 



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 56

def present_var_indices
  is_present = Array.new(@variable_index.count, false)
  @col_idx.each do |col_idx|
    is_present[col_idx] = true
  end
  is_present
end

#restrict_to_n_constraints(nb_constraints) ⇒ Object 



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# File 'lib/ruby-cbc/utils/compressed_row_storage.rb', line 44

def restrict_to_n_constraints(nb_constraints)
  length_of_values = @row_ptr[nb_constraints]
  CompressedRowStorage.new.tap do |crs|
    crs.model = @model.clone
    crs.variable_index = @variable_index
    crs.row_ptr = @row_ptr[0, nb_constraints + 1]
    crs.col_idx = @col_idx[0, length_of_values]
    crs.values = @values[0, length_of_values]
    crs.delete_missing_vars
  end
end