src/ieee754/part/layout_experiment.py

   1 #!/usr/bin/env python3
   2 # SPDX-License-Identifier: LGPL-3-or-later
   3 # See Notices.txt for copyright information
   4 """
   5 Links:
   6 * https://libre-soc.org/3d_gpu/architecture/dynamic_simd/shape/
   7 * https://bugs.libre-soc.org/show_bug.cgi?id=713#c20
   8 * https://bugs.libre-soc.org/show_bug.cgi?id=713#c30
   9 """
  10
  11 from nmigen import Signal, Module, Elaboratable, Mux, Cat, Shape, Repl
  12 from nmigen.back.pysim import Simulator, Delay, Settle
  13 from nmigen.cli import rtlil
  14
  15 from collections.abc import Mapping
  16 from functools import reduce
  17 import operator
  18 from collections import defaultdict
  19 from pprint import pprint
  20
  21 from ieee754.part_mul_add.partpoints import PartitionPoints
  22
  23
  24 # main fn
  25 def layout(elwid, signed, part_counts, lane_shapes):
  26     # identify if the lane_shapes is a mapping (dict, etc.)
  27     # if not, then assume that it is an integer (width) that
  28     # needs to be requested across all partitions
  29     if not isinstance(lane_shapes, Mapping):
  30         lane_shapes = {i: lane_shapes for i in part_counts}
  31     # compute a set of partition widths
  32     part_wid = -min(-lane_shapes[i] // c for i, c in part_counts.items())
  33     part_count = max(part_counts.values())
  34     # calculate the minumum width required
  35     width = part_wid * part_count
  36     # create the breakpoints dictionary.
  37     # do multi-stage version https://bugs.libre-soc.org/show_bug.cgi?id=713#c34
  38     # https://stackoverflow.com/questions/26367812/
  39     dpoints = defaultdict(list) # if empty key, create a (empty) list
  40     for i, c in part_counts.items():
  41         def add_p(p):
  42             dpoints[p].append(i) # auto-creates list if key non-existent
  43         for start in range(0, part_count, c):
  44             add_p(start * part_wid) # start of lane
  45             add_p(start * part_wid + lane_shapes[i]) # start of padding
  46     # do not need the breakpoints at the very start or the very end
  47     dpoints.pop(0, None)
  48     dpoints.pop(width, None)
  49     # second stage, add (map to) the elwidth==i expressions
  50     points = {}
  51     for p in dpoints.keys():
  52         points[p] = map(lambda i: elwid == i, dpoints[p])
  53         points[p] = reduce(operator.or_, points[p])
  54     # third stage, create the binary values which *if* elwidth is set to i
  55     # *would* result in the mask at that elwidth being set to this value
  56     # these can easily be double-checked through Assertion
  57     plist = list(points.keys())
  58     plist.sort()
  59     bitp = {}
  60     for i in part_counts.keys():
  61         bitp[i] = 0
  62         for p, elwidths in dpoints.items():
  63             if i in elwidths:
  64                bitpos = plist.index(p)
  65                bitp[i] |= 1<< bitpos
  66     return (PartitionPoints(points), bitp, width, lane_shapes,
  67         part_wid, part_count)
  68
  69 if __name__ == '__main__':
  70     part_counts = {
  71         0: 1,
  72         1: 1,
  73         2: 2,
  74         3: 4,
  75     }
  76
  77     for i in range(4):
  78         pprint((i, layout(i, True, part_counts, 3)))
  79
  80     l = {0: 5, 1: 6, 2: 12, 3: 24}
  81     for i in range(4):
  82         pprint((i, layout(i, False, part_counts, l)))
  83
  84     # https://bugs.libre-soc.org/show_bug.cgi?id=713#c30
  85     elwid = Signal(2)
  86     pp,bitp,b,c,d,e = layout(elwid, False, part_counts, l)
  87     pprint ((pp,b,c,d,e))
  88     for k, v in bitp.items():
  89         print ("bitp elwidth=%d" % k, bin(v))
  90
  91     m = Module()
  92     def process():
  93         for i in range(4):
  94             yield elwid.eq(i)
  95             yield Settle()
  96             ppt = []
  97             for pval in list(pp.values()):
  98                 val = yield pval # get nmigen to evaluate pp
  99                 ppt.append(val)
 100             pprint((i, (ppt,b,c,d,e)))
 101             # check the results against bitp static-expected partition points
 102             # https://bugs.libre-soc.org/show_bug.cgi?id=713#c47
 103             # https://stackoverflow.com/a/27165694
 104             ival = int(''.join(map(str, map(int, ppt))), 2)
 105             assert ival == bitp[i]
 106
 107     sim = Simulator(m)
 108     sim.add_process(process)
 109     sim.run()