From ba8ad1949c9e55def7da14ef30ffb2bcb7ffe19d Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Wed, 13 Oct 2021 16:09:11 +0100
Subject: [PATCH] add FP "exponent" example, not quite matching expected
 results needs analysis

---
 src/ieee754/part/layout_experiment.py | 51 ++++++++++++++++++++++++---
 1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/src/ieee754/part/layout_experiment.py b/src/ieee754/part/layout_experiment.py
index ccfd2517..f7b3586e 100644
--- a/src/ieee754/part/layout_experiment.py
+++ b/src/ieee754/part/layout_experiment.py
@@ -144,19 +144,24 @@ def layout(elwid, vec_el_counts, lane_shapes=None, fixed_width=None):
     # https://stackoverflow.com/questions/26367812/
     dpoints = defaultdict(list)  # if empty key, create a (empty) list
     for i, c in vec_el_counts.items():
+        print ("dpoints", i, "count", c)
         # calculate part_wid based on overall width divided by number
         # of elements.
         part_wid = width // c
-        def add_p(p):
+        def add_p(msg, start, p):
+            print ("    adding dpoint", msg, start, part_wid, i, c, p)
             dpoints[p].append(i)  # auto-creates list if key non-existent
         # for each elwidth, create the required number of vector elements
         for start in range(c):
-            add_p(start * part_wid)  # start of lane
-            add_p(start * part_wid + lane_shapes[i])  # start of padding
+            add_p("start", start, start * part_wid) # start of lane
+            add_p("end  ", start, start * part_wid + lane_shapes[i]) # end lane
 
     # do not need the breakpoints at the very start or the very end
     dpoints.pop(0, None)
-    dpoints.pop(width, None)
+    if fixed_width is not None:
+        dpoints.pop(fixed_width, None)
+    else:
+        dpoints.pop(width, None)
     plist = list(dpoints.keys())
     plist.sort()
     print("dpoints")
@@ -327,3 +332,41 @@ if __name__ == '__main__':
     for i in range(4):
         pprint((i, layout(i, vec_el_counts, fixed_width=32)))
 
+    # example "exponent"
+    #  https://libre-soc.org/3d_gpu/architecture/dynamic_simd/shape/
+    # 1xFP64: 11 bits, one exponent
+    # 2xFP32: 8 bits, two exponents
+    # 4xFP16: 5 bits, four exponents
+    # 4xBF16: 8 bits, four exponents
+    vec_el_counts = {
+        0: 1,  # QTY 1x FP64
+        1: 2,  # QTY 2x FP32
+        2: 4,  # QTY 4x FP16
+        3: 4,  # QTY 4x BF16
+    }
+    widths_at_elwidth = {
+        0: 11, # FP64 ew=0b00
+        1: 8,  # FP32 ew=0b01
+        2: 5,  # FP16 ew=0b10
+        3: 8   # BF16 ew=0b11
+    }
+
+    # expected results:
+    #
+    #        |31|  |  |24|     16|15  |  |   8|7     0 |
+    #        |31|28|26|24| |20|16|  12|  |10|8|5|4   0 |
+    #  32bit | x| x| x|  |      x|   x| x|10 ....    0 |
+    #  16bit | x| x|26    ... 16 |   x| x|10 ....    0 |
+    #  8bit  | x|28 .. 24|  20.16|   x|11 .. 8|x|4.. 0 |
+    #  unused  x                     x
+
+    print ("11,8,5,8 elements (FP64/32/16/BF exponents)", widths_at_elwidth)
+    for i in range(4):
+        pp, bitp, bm, b, c, d = \
+                    layout(i, vec_el_counts, widths_at_elwidth,
+                           fixed_width=32)
+        pprint((i, (pp, bitp, bm, b, c, d)))
+    # now check that the expected partition points occur
+    print("11,8,5,8 pp keys", pp.keys())
+    #assert list(pp.keys()) == [5,6,12,18]
+
-- 
2.30.2