From Primitive Performance, Dyalog ’13.
x←?1e6⍴1000 a. ¯1+{≢⍵}⌸(⍳1000),x 1.00 b. ¯1+{≢⍵}⌸(⍳1+⌈/x),x 1.62 max=*x++; for(i=1;i<n;++i){if(max<*x)max=*x; ++x;}
SSE4 (Intel) or AltiVec (IBM), circa 2008