src/openpower/decoder/isa/fastdctlee.py

   1 #
   2 # Fast discrete cosine transform algorithms (Python)
   3 #
   4 # Copyright (c) 2020 Project Nayuki. (MIT License)
   5 # https://www.nayuki.io/page/fast-discrete-cosine-transform-algorithms
   6 #
   7 # Permission is hereby granted, free of charge, to any person obtaining a copy of
   8 # this software and associated documentation files (the "Software"), to deal in
   9 # the Software without restriction, including without limitation the rights to
  10 # use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
  11 # the Software, and to permit persons to whom the Software is furnished to do so,
  12 # subject to the following conditions:
  13 # - The above copyright notice and this permission notice shall be included in
  14 #   all copies or substantial portions of the Software.
  15 # - The Software is provided "as is", without warranty of any kind, express or
  16 #   implied, including but not limited to the warranties of merchantability,
  17 #   fitness for a particular purpose and noninfringement. In no event shall the
  18 #   authors or copyright holders be liable for any claim, damages or other
  19 #   liability, whether in an action of contract, tort or otherwise, arising from,
  20 #   out of or in connection with the Software or the use or other dealings in the
  21 #   Software.
  22 #
  23
  24 import math
  25 from copy import deepcopy
  26
  27 # bits of the integer 'val'.
  28 def reverse_bits(val, width):
  29     result = 0
  30     for _ in range(width):
  31         result = (result << 1) | (val & 1)
  32         val >>= 1
  33     return result
  34
  35
  36 # DCT type II, unscaled. Algorithm by Byeong Gi Lee, 1984.
  37 # See: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.118.3056&rep=rep1&type=pdf#page=34
  38 def transform(vector, indent=0):
  39     idt = "   " * indent
  40     n = len(vector)
  41     if n == 1:
  42         return list(vector)
  43     elif n == 0 or n % 2 != 0:
  44         raise ValueError()
  45     else:
  46         half = n // 2
  47         alpha = [(vector[i] + vector[-(i + 1)]) for i in range(half)]
  48         beta  = [(vector[i] - vector[-(i + 1)]) /
  49                  (math.cos((i + 0.5) * math.pi / n) * 2.0)
  50                     for i in range(half)]
  51         alpha = transform(alpha)
  52         beta  = transform(beta )
  53         result = []
  54         for i in range(half - 1):
  55             result.append(alpha[i])
  56             result.append(beta[i] + beta[i + 1])
  57         result.append(alpha[-1])
  58         result.append(beta [-1])
  59         return result
  60
  61
  62 def transform(vector, indent=0):
  63     idt = "   " * indent
  64     n = len(vector)
  65     if n == 1:
  66         return list(vector)
  67     elif n == 0 or n % 2 != 0:
  68         raise ValueError()
  69     else:
  70         half = n // 2
  71         alpha = [0] * half
  72         beta = [0] * half
  73         print (idt, "xf", vector)
  74         print (idt, "coeff", n, "->", end=" ")
  75         for i in range(half):
  76             t1, t2 = vector[i], vector[n-i-1]
  77             k = (math.cos((i + 0.5) * math.pi / n) * 2.0)
  78             print (i, n-i-1, "i/n", (i+0.5)/n, ":", k, end= " ")
  79             alpha[i] = t1 + t2
  80             beta[i] = (t1 - t2) * (1/k)
  81         print ()
  82         print (idt, "n", n, "alpha", end=" ")
  83         for i in range(0, n, 2):
  84             print (i, i//2, alpha[i//2], end=" ")
  85         print()
  86         print (idt, "n", n, "beta", end=" ")
  87         for i in range(0, n, 2):
  88             print (i, beta[i//2], end=" ")
  89         print()
  90         alpha = transform(alpha, indent+1)
  91         beta  = transform(beta , indent+1)
  92         result = [0] * n
  93         for i in range(half):
  94             result[i*2] = alpha[i]
  95             result[i*2+1] = beta[i]
  96         print(idt, "merge", result)
  97         for i in range(half - 1):
  98             result[i*2+1] += result[i*2+3]
  99         print(idt, "result", result)
 100         return result
 101
 102
 103 def transform_itersum(vector, indent=0):
 104     idt = "   " * indent
 105     n = len(vector)
 106     if n == 1:
 107         return list(vector)
 108     elif n == 0 or n % 2 != 0:
 109         raise ValueError()
 110     else:
 111         half = n // 2
 112         alpha = [0] * half
 113         beta = [0] * half
 114         for i in range(half):
 115             t1, t2 = vector[i], vector[i+half]
 116             alpha[i] = t1
 117             beta[i] = t2
 118         alpha = transform_itersum(alpha, indent+1)
 119         beta  = transform_itersum(beta , indent+1)
 120         result = [0] * n
 121         for i in range(half):
 122             result[i*2] = alpha[i]
 123             result[i*2+1] = beta[i]
 124         print(idt, "iter-merge", result)
 125         for i in range(half - 1):
 126             result[i*2+1] += result[i*2+3]
 127         print(idt, "iter-result", result)
 128         return result
 129
 130
 131
 132 def transform2(vec, reverse=True):
 133
 134     vec = deepcopy(vec)
 135     # Initialization
 136     n = len(vec)
 137     print ()
 138     print ("transform2", n)
 139     levels = n.bit_length() - 1
 140
 141     # reference (read/write) the in-place data in *reverse-bit-order*
 142     if reverse:
 143         ri = list(range(n))
 144         ri = [ri[reverse_bits(i, levels)] for i in range(n)]
 145
 146     if reverse:
 147         vec = [vec[reverse_bits(i, levels)] for i in range(n)]
 148
 149     if False:
 150         size = n
 151         #v = list(range(n))
 152         v = deepcopy(ri)
 153         while size >= 2:
 154             halfsize = size // 2
 155             tablestep = n // size
 156             ir = list(range(0, n, size))
 157             for i in ir:
 158                 k = 0
 159                 j = list(range(i, i + halfsize))
 160                 jr = list(range(i+halfsize, i + size))
 161                 jr.reverse()
 162                 print ("  xform jr", j, jr)
 163                 vec2 = deepcopy(v)
 164                 for ci, (jl, jh) in enumerate(zip(j, jr)):
 165                     t1, t2 = v[ri[jl]], v[ri[jh]]
 166                     vec2[ri[jl]] = t1
 167                     vec2[ri[jl+halfsize]] = t2
 168                 v = vec2
 169             size //= 2
 170
 171         print ("ri rev", ri)
 172         print ("rh rev", v)
 173
 174         #vec2 = deepcopy(vec)
 175         #for i in range(n):
 176         #    vec[i] = vec2[v[i]]
 177
 178         ri = v
 179
 180     size = n
 181     while size >= 2:
 182         halfsize = size // 2
 183         tablestep = n // size
 184         ir = list(range(0, n, size))
 185         print ("  xform", size, ir)
 186         for i in ir:
 187             k = 0
 188             j = list(range(i, i + halfsize))
 189             jr = list(range(i+halfsize, i + size))
 190             jr.reverse()
 191             print ("  xform jr", j, jr)
 192             vec2 = deepcopy(vec)
 193             for ci, (jl, jh) in enumerate(zip(j, jr)):
 194                 t1, t2 = vec[ri[jl]], vec[ri[jh]]
 195                 coeff = (math.cos((ci + 0.5) * math.pi / size) * 2.0)
 196                 vec2[ri[jl]] = t1 + t2
 197                 vec2[ri[jl+halfsize]] = (t1 - t2) * (1/coeff)
 198                 print ("coeff", size, i, k, "jl", jl, "jh", jh,
 199                        "i/n", (k+0.5)/size, coeff, vec[ri[jl]], vec[ri[jh]])
 200                 k += tablestep
 201             vec = vec2
 202         size //= 2
 203
 204     print("transform2 pre-itersum", vec)
 205
 206     n = len(vec)
 207     size = n // 2
 208     while size >= 2:
 209         halfsize = size // 2
 210         ir = list(range(0, halfsize))
 211         print ("itersum", halfsize, size, ir)
 212         for i in ir:
 213             jr = list(range(i+halfsize, i+n-halfsize, size))
 214             print ("itersum    jr", i+halfsize, i+size, jr)
 215             for jh in jr:
 216                 vec[jh] += vec[jh+size]
 217                 print ("    itersum", size, i, jh, jh+size)
 218         size //= 2
 219
 220     print("transform2 result", vec)
 221
 222     return vec
 223
 224
 225 # DCT type III, unscaled. Algorithm by Byeong Gi Lee, 1984.
 226 # See: https://www.nayuki.io/res/fast-discrete-cosine-transform-algorithms/lee-new-algo-discrete-cosine-transform.pdf
 227 def inverse_transform(vector, root=True, indent=0):
 228     idt = "   " * indent
 229     if root:
 230         vector = list(vector)
 231         vector[0] /= 2
 232     n = len(vector)
 233     if n == 1:
 234         return vector, [0]
 235     elif n == 0 or n % 2 != 0:
 236         raise ValueError()
 237     else:
 238         half = n // 2
 239         alpha = [vector[0]]
 240         beta  = [vector[1]]
 241         for i in range(2, n, 2):
 242             alpha.append(vector[i])
 243             beta.append(vector[i - 1] + vector[i + 1])
 244         print (idt, "n", n, "alpha 0", end=" ")
 245         for i in range(2, n, 2):
 246             print (i, end=" ")
 247         print ("beta 1", end=" ")
 248         for i in range(2, n, 2):
 249             print ("%d+%d" % (i-1, i+1), end=" ")
 250         print()
 251         inverse_transform(alpha, False, indent+1)
 252         inverse_transform(beta , False, indent+1)
 253         for i in range(half):
 254             x = alpha[i]
 255             y = beta[i] / (math.cos((i + 0.5) * math.pi / n) * 2)
 256             vector[i] = x + y
 257             vector[-(i + 1)] = x - y
 258             print (idt, " v[%d] = alpha[%d]+beta[%d]" % (i, i, i))
 259             print (idt, " v[%d] = alpha[%d]-beta[%d]" % (n-i-1, i, i))
 260         return vector
 261
 262
 263 def inverse_transform2(vector, root=True):
 264     n = len(vector)
 265     if root:
 266         vector = list(vector)
 267     if n == 1:
 268         return vector
 269     elif n == 0 or n % 2 != 0:
 270         raise ValueError()
 271     else:
 272         half = n // 2
 273         alpha = [0]
 274         beta  = [1]
 275         for i in range(2, n, 2):
 276             alpha.append(i)
 277             beta.append(("add", i - 1, i + 1))
 278         inverse_transform2(alpha, False)
 279         inverse_transform2(beta , False)
 280         for i in range(half):
 281             x = alpha[i]
 282             y = ("cos", beta[i], i)
 283             vector[i] = ("add", x, y)
 284             vector[-(i + 1)] = ("sub", x, y)
 285         return vector
 286
 287
 288 def failllll_transform2(block):
 289     N = len(block)
 290     cos = [0.0] * (N>>1)
 291
 292     front = deepcopy(block)
 293     back = deepcopy(block)
 294
 295     step = 1
 296     j = N *2
 297     half_N = N
 298     prev_half_N = N
 299
 300     while j > 1: #// Cycle of iterations Input Butterfly
 301         half_N = half_N >> 1
 302         current_PI_half_By_N = (math.pi / 2) / prev_half_N
 303         current_PI_By_N = 0.0
 304         step_Phase = current_PI_half_By_N * 2.0
 305         print ("n", N, "cos", end=" ")
 306         for i in range(half_N):
 307             #Precompute Cosine's coefficients
 308             a = current_PI_By_N + current_PI_half_By_N
 309             print (i, a / (math.pi), math.cos(a) * 2, end=" ")
 310             cos[i] = 0.5 / math.cos(a)
 311             current_PI_By_N += step_Phase
 312         print()
 313         k = 0
 314         for x in range(step):
 315             for i in range(half_N):
 316                 shift = k + prev_half_N - i - 1
 317                 back[k + i]          = front[k + i] + front[shift]
 318                 back[k + half_N + i] = (front[k + i] - front[shift]) * cos[i]
 319                 print ("xf coeff", N, j, i, x, "k/kh", k+i, k+half_N+i)
 320             k += prev_half_N
 321         temp = front
 322         front = back
 323         back = temp
 324         j = j >> 1
 325         step = step << 1
 326         prev_half_N = half_N
 327
 328     half_N = 2
 329     prev_half_N = 2
 330     j = 2
 331
 332     print("xform intermediate", front)
 333
 334     while j < N: # Cycle of Out ButterFly
 335         k = 0
 336         print ("out", j, N, step, half_N)
 337         for x in range(step):
 338             for i in range(half_N - 1):
 339                 back[k + (i << 1)] = front[k + i]
 340                 back[k + (i << 1) + 1] = (front[k + half_N + i] +
 341                                           front[k + half_N + i + 1])
 342                 print ("  out", j, x, i, "k", k,
 343                                 "k+i<<1", k+(i<<1), "hh1", k+half_N+i)
 344             back[k + ((half_N - 1) << 1)] = front[k + half_N - 1]
 345             back[k + (half_N << 1) - 1] = front[k + (half_N << 1) - 1]
 346             k += prev_half_N
 347
 348         temp = front
 349         front = back
 350         back = temp
 351         j = j << 1
 352         step = step >> 1
 353         half_N = prev_half_N
 354         prev_half_N = prev_half_N << 1
 355
 356     for i in range(N):
 357         block[i] = front[i] #// Unload DCT coefficients
 358     dN = 2.0
 359     #block[0] = block[0] / dN #// Compute DC.
 360
 361     print("transform2 result", block)
 362     return block
 363
 364
 365 def itersum_explore(vector, indent=0):
 366     idt = "   " * indent
 367     n = len(vector)
 368     if n == 1:
 369         return list(vector)
 370     elif n == 0 or n % 2 != 0:
 371         raise ValueError()
 372     else:
 373         half = n // 2
 374         alpha = [0] * half
 375         beta = [0] * half
 376         for i in range(half):
 377             t1, t2 = vector[i], vector[i+half]
 378             alpha[i] = t1
 379             beta[i] = t2
 380         alpha = itersum_explore(alpha, indent+1)
 381         beta  = itersum_explore(beta , indent+1)
 382         result = [0] * n
 383         for i in range(half):
 384             result[i*2] = alpha[i]
 385             result[i*2+1] = beta[i]
 386         print(idt, "iter-merge", result)
 387         for i in range(half - 1):
 388             result[i*2+1] = ("add", result[i*2+1], result[i*2+3])
 389         print(idt, "iter-result", result)
 390         return result
 391
 392
 393 def itersum_explore2(vec, indent=0):
 394     n = len(vec)
 395     size = n // 2
 396     while size >= 2:
 397         halfsize = size // 2
 398         ir = list(range(0, halfsize))
 399         #ir.reverse()
 400         print ("itersum", halfsize, size, ir)
 401         for i in ir:
 402             jr = list(range(i+halfsize, i+n-halfsize, size))
 403             print ("itersum    jr", i+halfsize, i+size, jr)
 404             for jh in jr:
 405                 vec[jh] = ("add", vec[jh], vec[jh+size])
 406                 print ("    itersum", size, i, jh, jh+size)
 407         size //= 2
 408
 409     #if reverse:
 410     #    vec = [vec[reverse_bits(i, levels)] for i in range(n)]
 411
 412     return vec
 413
 414 if __name__ == '__main__':
 415     n = 16
 416     vec = list(range(n))
 417     levels = n.bit_length() - 1
 418     vec = [vec[reverse_bits(i, levels)] for i in range(n)]
 419     ops = itersum_explore(vec)
 420     #ops = [ops[reverse_bits(i, levels)] for i in range(n)]
 421     for i, x in enumerate(ops):
 422         print (i, x)
 423
 424     n = 16
 425     vec = list(range(n))
 426     levels = n.bit_length() - 1
 427     #vec = [vec[reverse_bits(i, levels)] for i in range(n)]
 428     ops = itersum_explore2(vec)
 429     for i, x in enumerate(ops):
 430         print (i, x)