Abstract: This paper discusses some advanced vectorization techniques related to interchangingDO loops and breaking recurrences.Several rules of loop interchanging on vector computer KJ8920 arepresented for multiply-nested DO loops.For multiple loops satisfying the conditions of interchanging,the exact loop bound expressions after interchanging are given if the bounds of the inner DO loopare invariants or strictly monotone functions of the outer loop index.Based on the relevance analysisapproach,we represent the optimal interval segmentation algorithm,which removes the cycle from thedependence graph by dividing the interval of DO loops.