In addition to the substance in phonology, a number of researchers have argued that computation also matters in phonology. Using the data in Yavapai (Yuman language), I show that other than an OT analysis focusing mainly on substance, a computational analysis is necessary for explaining the complex syllabification processes and the frequencies of optional surface representations due to different syllabifications. I will use computational complexity encoded in subregular hierarchy as the main technical tool in the computational analysis. Our main hypothesis is that when both SRs are well-formed based on the syllable phonotactics, the one less complex to generate is more frequently attested. The paper shows that the syllabification pattern in Yavapai necessarily requires a computational motivation, which in turn shows that computational property is a crucial factor in phonological transformations.