simple_v_extension/shape_table_format.mdwn

   1 Shape is 32-bits When SHAPE is set entirely to zeros, remapping is
   2 disabled: the register's elements are a linear (1D) vector.
   3
   4 | 31..30   | 29..24 | 23..21  | 20..18  | 17..12  | 11..6   | 5..0    |
   5 | -------- | ------ | ------- | ------- | ------- | -------- | ------- |
   6 | applydim |modulo | invxyz | permute | zdimsz  | ydimsz  | xdimsz  |
   7
   8 applydim will set to zero the dimensions less than this. applydim=0 applies all three. applydim=1 applies y and z. applydim=2 applys only z. applydim=3 is reserved.
   9
  10 invxyz will invert the start index of each of x, y or z. If invxyz[0] is zero then x-dimensional counting begins from 0 and increments, otherwise it begins from xdimsz-1 and iterates down to zero. Likewise for y and z.
  11
  12 modulo will cause the output to wrap and remain within the range 0 to modulo. The value zero disables modulus application. Note that modulo arithmetic is applied after all other remapping calculations.
  13
  14 xdimsz, ydimsz and zdimsz are offset by 1, such that a value of 0 indicates
  15 that the array dimensionality for that dimension is 1.  A value of xdimsz=2
  16 would indicate that in the first dimension there are 3 elements in the
  17 array.  The format of the array is therefore as follows:
  18
  19     array[xdim+1][ydim+1][zdim+1]
  20
  21 However whilst illustrative of the dimensionality, that does not take the
  22 "permute" setting into account.  "permute" may be any one of six values
  23 (0-5, with values of 6 and 7 being reserved, and not legal).  The table
  24 below shows how the permutation dimensionality order works:
  25
  26 | permute | order | array format             |
  27 | ------- | ----- | ------------------------ |
  28 | 000     | 0,1,2 | (xdim+1)(ydim+1)(zdim+1) |
  29 | 001     | 0,2,1 | (xdim+1)(zdim+1)(ydim+1) |
  30 | 010     | 1,0,2 | (ydim+1)(xdim+1)(zdim+1) |
  31 | 011     | 1,2,0 | (ydim+1)(zdim+1)(xdim+1) |
  32 | 100     | 2,0,1 | (zdim+1)(xdim+1)(ydim+1) |
  33 | 101     | 2,1,0 | (zdim+1)(ydim+1)(xdim+1) |
  34
  35 In other words, the "permute" option changes the order in which
  36 nested for-loops over the array would be done.
  37