In cases where an array is used to simulate a cylindrical coordinate system, where the left edge of the array must be adjacent to its right edge, a "wraparound variable" is often used, as follows:

jm1 = n; for ( j=0; j<n; j++ ) { b[j] = (a[j] + a[jm1]) / 2; jm1 = j; }

In the first iteration, `jm1`

is `n`

.
In all iterations except for `j=0`

, the value of
`jm1`

is `j-1`

. Thus, `jm1`

is
an induction variable for the loop after the first iteration.

By peeling off the first iteration of the loop, the `jm1`

induction variable can be exploited, as follows:

if (n >= 1) { b[0] = (a[0] + a[n]) / 2; for ( j = 1; j<n; j++ ) { b[j] = (a[j] + a[j-1]) / 2; } }

KAP may peel off several iterations in cases where multiple wraparound variables exist.

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