ðə bˈeɪsɪk aɪdˈiə ɪz tʊ aɪdˈɛntᵻfˌaɪ "dˈɛd ˈɛndz", ˈaɪ.ˈiː., kˌɑːmbᵻnˈeɪʃənz ʌv vˈɛɹɪəbəlz ðæt ɑːɹ nˌɑːt nˈɛsᵻsɚɹi tə dᵻfˈaɪn ɐ ɡlˈoʊbəl mˈɪnɪməm bɪkˈʌz ðɛɹ ɪz ˈɔːlweɪz ɐ wˈeɪ ʌv ɹᵻplˈeɪsɪŋ sˈʌtʃ kˌɑːmbᵻnˈeɪʃən baɪ ɐ bˈɛɾɚ ɔːɹ ɪkwˈɪvələnt wˌʌn.
The basic idea is to identify "dead ends", i.e., combinations of variables that are not necessary to define a global minimum because there is always a way of replacing such combination by a better or equivalent one.