code: function(options, cb) {
  
        // if no sassDir or files are not identify, error.
        if (!options.sassDir) {
          grunt.log.error('compass-multiple needs sassDir for searching scss files.');
          cb(false);
        }
  
        // search scss files.(Additional Implementation)
        if (options.sassFiles) {
  
          var pathes = options.sassFiles;
          var pathesCount = pathes.length;
          var currentCount = 0;
          var files = [];
          for (var i = 0; i < pathes.length; i++) {
            glob(pathes[i], function(error, tmpFiles) {
              if (error) {
                console.log('error: ', error);
                cb(false);
              }
  
              files = files.concat(tmpFiles);
              currentCount++;
              if (pathesCount === currentCount) {
                // compass compile.
                grunt.log.writeln('pathes: ', files);
                compileFiles(options, files, cb);
              }
            });
          }
  
  
  
  
        } else {  // use sassDir
  
  
          var searchPath = options.sassDir + '/**/*.scss';
          glob(searchPath, function(error, files) {
            if (error) {
              console.log('error: ', error);
              cb(false);
            }
  
            // compass compile.
            compileFiles(options, files, cb);
          });
  
  
  
  
        }
      }
docs: compass task works at multi threads.