[Core Utils] Added unpack innermost dim from hex string function

src/finn/core/utils.py

+import os
 import random
 import string
 import subprocess
-import os
 
 import numpy as np
 import onnx
@@ -111,6 +111,37 @@ def pack_innermost_dim_as_hex_string(ndarray, dtype, pad_to_nbits):
     return np.apply_along_axis(fun, ndarray.ndim - 1, ndarray)
 
 
+def unpack_innermost_dim_from_hex_string(data, shape, packedBits, targetBits):
+    # function expects flattens array and returns an array in the desired shape
+    outer_dim_elems = 1
+    for dim in range(len(shape) - 1):
+        outer_dim_elems = outer_dim_elems * shape[dim]
+    inner_dim_elems = shape[-1]
+
+    array = []
+    for outer_elem in range(outer_dim_elems):
+        ar_list = []
+        ar_elem = data[0]
+        data.pop(0)
+        ar_elem = ar_elem.split("x")
+        ar_elem_bin = bin(int(ar_elem[1], 16))[2:].zfill(packedBits)
+        ar_elem_bin = [int(x) for x in ar_elem_bin]
+
+        ar_elem_bin.reverse()
+        for i in range(inner_dim_elems):
+            upper_limit = (i + 1) * targetBits
+            lower_limit = i * targetBits
+            elem = ar_elem_bin[lower_limit:upper_limit]
+            elem.reverse()
+            elem_str = "".join(map(str, elem))
+            ar_list.append(int(elem_str, 2))
+        ar_list.reverse()
+        array.append(ar_list)
+
+    array = np.asarray(array, dtype=np.float32).reshape(shape)
+    return array
+
+
 def interleave_matrix_outer_dim_from_partitions(matrix, n_partitions):
     if type(matrix) != np.ndarray or matrix.dtype != np.float32:
         # try to convert to a float numpy array (container dtype is float)
@@ -202,7 +233,7 @@ def calculate_signed_dot_prod_range(dt_a, dt_b, len):
     types dt_a and dt_b of len elements can take."""
     assert dt_a.signed() and dt_b.signed()
     min_prod = 2 ** 30
-    max_prod = -2 ** 30
+    max_prod = -(2 ** 30)
     for a_val in [dt_a.min(), dt_a.max()]:
         for b_val in [dt_b.min(), dt_b.max()]:
             prod = a_val * b_val * len
@@ -250,12 +281,13 @@ class CppBuilder:
         process_compile = subprocess.Popen(bash_command, stdout=subprocess.PIPE)
         process_compile.communicate()
 
+
 class IPGenBuilder:
     def __init__(self):
         self.tcl_script = ""
         self.ipgen_path = ""
         self.code_gen_dir = ""
-        self.ipgen_script=""
+        self.ipgen_script = ""
 
     def append_tcl(self, tcl_script):
         self.tcl_script = tcl_script
@@ -276,4 +308,3 @@ class IPGenBuilder:
         bash_command = ["bash", self.ipgen_script]
         process_compile = subprocess.Popen(bash_command, stdout=subprocess.PIPE)
         process_compile.communicate()
-