[Exec] enable optional scale/shift args for multithresholding

src/finn/core/multithreshold.py

@@ -8,7 +8,7 @@ def compare(x, y):
         return 0.0
 
 
-def execute(v, thresholds):
+def execute(v, thresholds, out_scale=1.0, out_bias=0.0):
 
     # the inputs are expected to be in the shape (N,C,H,W)
     # N : Batch size
@@ -21,6 +21,8 @@ def execute(v, thresholds):
     #     if all channels use the same threshold value)
     # B : Desired activation steps => i.e. for 4-bit activation, B=7 (2^(n)-1 and n=4)
 
+    # the output tensor will be scaled by out_scale and biased by out_bias
+
     # assert threshold shape
     is_global_threshold = thresholds.shape[0] == 1
     assert (v.shape[1] == thresholds.shape[0]) or is_global_threshold
@@ -55,4 +57,4 @@ def execute(v, thresholds):
                     # apply successive thresholding to every element of one channel
                     ret[b][t][elem] += compare(vr[b][t][elem], channel_thresh[a])
 
-    return ret.reshape(v.shape)
+    return out_scale * ret.reshape(v.shape) + out_bias