Class: RedShift::RK4DifferentialFlow

Inherits:
Flow show all
Defined in:
lib/redshift/component.rb,
lib/redshift/target/c/flow/rk4.rb

Constant Summary

Constants inherited from Flow

Flow::CT_STRUCT_NAME

Instance Attribute Summary

Attributes inherited from Flow

#fname, #formula, #generator, #inspect_str, #strict, #var

Instance Method Summary collapse

Methods inherited from Flow

#become_generatable, #external_constant?, #generate, #initialize, #inspect, #make_ct_struct, #translate, #translate_link, #wrapper

Constructor Details

This class inherits a constructor from RedShift::Flow

Instance Method Details

#make_generator(cl, state) ⇒ Object 



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# File 'lib/redshift/target/c/flow/rk4.rb', line 2

def make_generator cl, state
  @fname = "flow_#{CGenerator.make_c_name cl.name}_#{var}_#{state}"
  @inspect_str = "#{cl.name}:#{state}: #{var} = #{formula}"

  @generator = proc do
    sl = cl.shadow_library
    ssn = cl.shadow_struct_name
    cont_state_ssn = cl.cont_state_class.shadow_struct_name

    sl.init_library_function.body \
      "s_init_flow(#{fname}, #{fname.inspect}, #{inspect_str.inspect}, NONALGEBRAIC);"

    include_file, source_file = sl.add_file fname
    
    # We need the struct
    source_file.include(cl.shadow_library_include_file)
    
    flow = self
    var_name = @var
    source_file.define(fname).instance_eval do
      arguments "ComponentShadow *comp_shdw"
      scope :extern
      declare :shadow => %{
        struct #{ssn} *shadow;
        struct #{cont_state_ssn} *cont_state;
        ContVar  *var;
        double    ddt_#{var_name};
        double    value_4;
        double    time_step;
      }
      setup :shadow => %{
        shadow = (#{ssn} *)comp_shdw;
        cont_state = (struct #{cont_state_ssn} *)shadow->cont_state;
        var = &cont_state->#{var_name};
        time_step = shadow->world->time_step;
      }
      setup :rk_level => %{
        shadow->world->rk_level--;
      } # has to happen before referenced alg flows are called in other setups
      body %{
        #{flow.translate(self, "ddt_#{var_name}", cl).join("
        ")};

        switch (shadow->world->rk_level) {
        case 0:
          var->value[1] = var->value[0] + ddt_#{var_name} * time_step/2;
          break;

        case 1:
          var->value[2] = var->value[0] + ddt_#{var_name} * time_step/2;
          break;

        case 2:
          var->value[3] = var->value[0] + ddt_#{var_name} * time_step;
          break;

        case 3:
          value_4 = var->value[0] + ddt_#{var_name} * time_step;
          var->value[0] =
            (-3*var->value[0] + 2*var->value[1] + 4*var->value[2] +
              2*var->value[3] + value_4) / 6;
          break;

        default:
          rb_raise(#{declare_class RuntimeError},
            "Bad rk_level, %ld!", shadow->world->rk_level);
        }
        
        shadow->world->rk_level++;
        var->rk_level = shadow->world->rk_level;
      }
    end
  end
end