Simex | Rebel

Comparing similarity / originality between the Top-20 engines during the period of one year.

For the purpose we are using SIMEX, a tool that measures move similarities between engines using 8238 selected positions playing on depth=1, meaning that the main search is canceled and we mainly testing the evaluation of engines whether HCE or NNUE.

Situation August 2023

The then current top engines

The sudden high similarity between Rebel 16.3 and CSTAL is the result of equal source code but different NNUE's

Situation August 2024

A wave of new engines stormed the rating lists

We measured the similarity / originality of these engines ALSO with SIMEX.

And suddenly we get :

39. Engine motor-060 and Obsidian-11 show a similarity of 66.37%
43. Engine motor-060 and Obsidian-10 show a similarity of 66.07%
44. Engine motor-050 and Obsidian-11 show a similarity of 66.04%
45. Engine motor-060 and Obsidian-9 show a similarity of 66.04%
46. Engine stormphrax-4.1 and viridithas-12 show a similarity of 65.79%
51. Engine stormphrax-4.0 and viridithas-12 show a similarity of 65.59%
56. Engine stormphrax-4.1 and viridithas-11 show a similarity of 65.47%
58. Engine motor-050 and Obsidian-10 show a similarity of 65.35%
59. Engine motor-050 and Obsidian-9 show a similarity of 65.33%
60. Engine stormphrax-4.0 and viridithas-11 show a similarity of 65.29%
75. Engine stormphrax-4.1 and viridithas-10 show a similarity of 63.01%
77. Engine Obsidian-11 and PlentyChess-1.0.0 show a similarity of 62.86%
79. Engine motor-060 and PlentyChess-2.1.0 show a similarity of 62.83%
81. Engine stormphrax-4.0 and viridithas-10 show a similarity of 62.77%
82. Engine stormphrax-5.0 and viridithas-13 show a similarity of 62.66%
83. Engine Obsidian-11 and PlentyChess-2.1.0 show a similarity of 62.61%
84. Engine Obsidian-12 and PlentyChess-2.1.0 show a similarity of 62.57%
85. Engine Obsidian-10 and PlentyChess-1.0.0 show a similarity of 62.53%
87. Engine Obsidian-9 and PlentyChess-1.0.0 show a similarity of 62.52%
88. Engine stormphrax-5.0 and viridithas-12 show a similarity of 62.39%
90. Engine Obsidian-10 and PlentyChess-2.1.0 show a similarity of 62.32%
91. Engine Obsidian-9 and PlentyChess-2.1.0 show a similarity of 62.32%
93. Engine Obsidian-11 and viridithas-11 show a similarity of 62.24%
94. Engine stormphrax-5.0 and viridithas-11 show a similarity of 62.13%
97. Engine Clarity-6.0 and viridithas-11 show a similarity of 62.01%
98. Engine Clarity-7.2 and motor-060 show a similarity of 61.99%
101. Engine motor-050 and viridithas-11 show a similarity of 61.86%
103. Engine motor-040 and PlentyChess-0.3.0 show a similarity of 61.84%
104. Engine motor-060 and PlentyChess-1.0.0 show a similarity of 61.81%
105. Engine Obsidian-10 and viridithas-11 show a similarity of 61.77%
106. Engine Obsidian-9 and viridithas-11 show a similarity of 61.75%
107. Engine Clarity-7.2 and PlentyChess-2.1.0 show a similarity of 61.73%
111. Engine Obsidian-11 and PlentyChess-0.3.0 show a similarity of 61.65%
112. Engine motor-050 and PlentyChess-0.3.0 show a similarity of 61.44%
113. Engine Obsidian-10 and PlentyChess-0.3.0 show a similarity of 61.41%
114. Engine Obsidian-9 and PlentyChess-0.3.0 show a similarity of 61.38%
117. Engine Clarity-7.2 and Obsidian-11 show a similarity of 61.19%
119. Engine stormphrax-4.1 and viridithas-13 show a similarity of 61.18%
120. Engine stormphrax-4.0 and viridithas-13 show a similarity of 61.15%
121. Engine motor-040 and Obsidian-11 show a similarity of 61.14%
127. Engine Lizard-10.2 and Obsidian-11 show a similarity of 60.93%
129. Engine motor-050 and PlentyChess-2.1.0 show a similarity of 60.84%
130. Engine motor-060 and viridithas-11 show a similarity of 60.81%
131. Engine motor-040 and Obsidian-10 show a similarity of 60.79%
132. Engine motor-040 and Obsidian-9 show a similarity of 60.77%
134. Engine Clarity-7.1 and motor-060 show a similarity of 60.76%
135. Engine Obsidian-13 and PlentyChess-2.1.0 show a similarity of 60.75%
138. Engine Clarity-7.0 and motor-060 show a similarity of 60.65%
139. Engine Clarity-7.2 and Obsidian-9 show a similarity of 60.60%
140. Engine Lizard-10.4 and Obsidian-13 show a similarity of 60.60%
141. Engine Clarity-7.2 and Obsidian-10 show a similarity of 60.59%
143. Engine motor-060 and Obsidian-12 show a similarity of 60.52%
144. Engine Lizard-10.2 and motor-050 show a similarity of 60.51%
145. Engine Clover-7.1 and Obsidian-12 show a similarity of 60.47%
146. Engine Clover-7.0 and Obsidian-12 show a similarity of 60.46%
147. Engine motor-050 and PlentyChess-1.0.0 show a similarity of 60.45%
148. Engine Clarity-7.1 and PlentyChess-2.1.0 show a similarity of 60.42%
149. Engine Lizard-10.2 and Obsidian-10 show a similarity of 60.40%
150. Engine Clarity-7.0 and PlentyChess-2.1.0 show a similarity of 60.39%
151. Engine Lizard-10.2 and Obsidian-9 show a similarity of 60.39%
152. Engine Clarity-7.0 and Obsidian-11 show a similarity of 60.36%
153. Engine Clarity-7.1 and Obsidian-11 show a similarity of 60.36%
154. Engine Clarity-7.2 and Obsidian-12 show a similarity of 60.30%
155. Engine Clarity-7.2 and motor-050 show a similarity of 60.29%
156. Engine Lizard-10.5 and Obsidian-13 show a similarity of 60.22%
158. Engine Clover-7.0 and viridithas-12 show a similarity of 60.19%
160. Engine Clarity-6.0 and viridithas-10 show a similarity of 60.03%
161. Engine Clarity-7.2 and PlentyChess-2.0.0 show a similarity of 60.03%
162. Engine Clover-7.0 and viridithas-11 show a similarity of 60.02%

Meaning there is a 15-20% increase of move similarity and thus a decrease of 15-20% in originality in one year.

We asked for an explanation but satisfying answers did not came.