question: private int calculateLog2N ( int nmax ) { int log2n ; log2n = ( int ) ( Math . log ( nmax ) / Math . log ( 2.0 ) + ROUNDING_HALF ) ; if ( nmax > 1 << log2n ) { log2n += 1 ; } return log2n ; }
target:  log2n is log2 of max(nx,ny) rounded up to next power of 2