+
    Time (s) vs. N (NxN submatrix, PDL: Double D [1500,1500] matrix)
      +-----------------------------------------------------------+
    2 |-+  +      +      +      +       +      +      +      +  +-|
      |                         C   C                             |
      |                                 C                         |
      |                      C                                    |
      |                      D  D   D   D  C                      |
  1.5 |-+  A             C                                      +-|
      |                  D                 D                      |
      |                                        C                  |
      |               C                        D                  |
      |                                                           |
      |     B         D                           D               |
    1 |-+                                                       +-|
      |           C                                               |
      |                                               C           |
      |           D                                   D           |
      |                                                           |
      |    A                                             D        |
  0.5 |-+      C                                                +-|
      |        D                                                  |
      |                                                           |
      |    B                                                 D    |
      |                                                           |
      |    DC                                                     |
    0 |-+  DD                                                   +-|
      |    +      +      +      +       +      +      +      +    |
      +-----------------------------------------------------------+
           0     200    400    600     800    1000   1200   1400
                         sms_WxH_PDL_naive    A
                      sms_WxH_pdlpp_4loops    B
                      sms_WxH_pdlpp_3loops    C
                          sms_WxH_PDL_lags    D
  +------+-------+-------+-------+-------+
  | N    | A     | B     | C     | D     |
  +------+-------+-------+-------+-------+
  | 2    | 0.038 | 0.009 | 0.009 | 0.047 |
  | 4    | 0.294 | 0.031 | 0.019 | 0.041 |
  | 6    | 0.572 | 0.072 | 0.019 | 0.044 |
  | 10   | 1.531 | 0.250 | 0.031 | 0.031 |
  | 20   |       | 1.150 | 0.072 | 0.022 |
  | 100  |       |       | 0.494 | 0.394 |
  | 200  |       |       | 0.931 | 0.797 |
  | 300  |       |       | 1.263 | 1.153 |
  | 400  |       |       | 1.544 | 1.431 |
  | 500  |       |       | 1.756 | 1.594 |
  | 600  |       |       | 1.869 | 1.653 |
  | 700  |       |       | 1.872 | 1.641 |
  | 800  |       |       | 1.788 | 1.594 |
  | 900  |       |       | 1.597 | 1.481 |
  | 1000 |       |       | 1.362 | 1.288 |
  | 1100 |       |       | 1.144 | 1.081 |
  | 1200 |       |       | 0.841 | 0.809 |
  | 1300 |       |       | 0.575 | 0.572 |
  | 1400 |       |       | 0.291 | 0.272 |
  +------+-------+-------+-------+-------+