| CSC300: XPerformanceOfArrays *1.5 [10/14] | |
01 |
public void push(double item) { if (N == a.length) resize((int)Math.ceil (N*1.5)); a[N] = item; N += 1; } |
Output
00 00 01 00 01 02 00 01 02 03 04 00 01 02 03 04 05 06 07 00 01 02 03 04 05 06 07 08 09 10 11 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Elapsed count f( 512): 1,922: 2.189 [ 0.000 : NaN] Elapsed count f( 1,024): 3,144: 1.636 [ 0.001 : Infinity] Elapsed count f( 2,048): 6,831: 2.173 [ 0.000 : 0.000] Elapsed count f( 4,096): 14,872: 2.177 [ 0.000 : NaN] Elapsed count f( 8,192): 32,453: 2.182 [ 0.001 : Infinity] Elapsed count f( 16,384): 52,782: 1.626 [ 0.002 : 2.000] Elapsed count f( 32,768): 114,681: 2.173 [ 0.002 : 1.000] Elapsed count f( 65,536): 249,859: 2.179 [ 0.003 : 1.500] Elapsed count f( 131,072): 407,564: 1.631 [ 0.004 : 1.333] Elapsed count f( 262,144): 884,271: 2.170 [ 0.006 : 1.500] Elapsed count f( 524,288): 1,924,095: 2.176 [ 0.012 : 2.000] Elapsed count f( 1,048,576): 3,148,295: 1.636 [ 0.020 : 1.667] Elapsed count f( 2,097,152): 6,821,541: 2.167 [ 0.039 : 1.950] Elapsed count f( 4,194,304): 14,824,201: 2.173 [ 0.042 : 1.077] Elapsed count f( 8,388,608): 32,305,900: 2.179 [ 0.147 : 3.500] Elapsed count f( 16,777,216): 52,653,164: 1.630 [ 0.150 : 1.020] Elapsed count f( 33,554,432): 114,275,340: 2.170 [ 0.508 : 3.387] Elapsed count f( 67,108,864): 248,730,932: 2.177 [ 1.268 : 2.496] Average delta: 2.025
N pushes in linear time
Each time we resize: constant pushes multiply by 1.5
Each push is ammortized constant time