The order and relationship of all tested architecture modifications (center), organized by instruction set series (left).

<p>The evolutionary potential of the architecture selected as the basis for further experiments in each series (shown in bold) is displayed (right) for the Logic-9, Logic-77, Match-12, Fibonacci-32, Sort-10, Limited-9, and Navigation environments, respectively. Up arrows (black) indicate increased potential, down arrows (gray) indicate decreased potential, and double ended arrows (white) denote no significant trend. In general, FA (fully-associative) and Split-IO (separated input and output operations) demonstrated broadly beneficial impacts on evolutionary potential. The remaining tested modifications highlight the robustness of digital evolution, exhibiting no systematic effects on evolutionary potential.</p

FLOW Series Architectures Fitness.

<p>Fitness results of the FLOW-series instruction set architectures. Each entry shows the median log population mean fitness in the respective environment, with confidence intervals in parentheses. Bold entries indicate significant (, Wilcoxon rank-sum test) deviations after sequential Bonferroni correction.</p

bf SPLIT-IO Architecture Fitness.

<p>Fitness results of the LABEL-SEQ-DIRECT and SPLIT-IO instruction set architectures. Each entry shows the median log population mean fitness in the respective environment, with confidence intervals in parentheses. Bold entries indicate significant (, Wilcoxon rank-sum test) deviations after sequential Bonferroni correction.</p

SEARCH Series Architectures Task Success.

<p>Task success results of the SEARCH-series instruction set architectures. Each entry shows the median normalized task success in the respective environment, with confidence intervals in parentheses. Bold entries denote significant (, Wilcoxon rank-sum test) deviations.</p

The architecture of the Avida virtual CPU.

<p>Registers (upper right), stacks (lower right), genomic program (left), heads (middle), and environmental channels (lower right). The solid lines depict the default Heads architectural features. The dashed lines show some of the modifications tested.</p

LABEL Series Architectures Fitness.

<p>Fitness results of the LABEL-series instruction set architectures. Each entry shows the median log population mean fitness in the respective environment, with confidence intervals in parentheses. Bold entries indicate significant (, Wilcoxon rank-sum test) deviations after sequential Bonferroni correction.</p

HEADS and HEADS-EX Architectures Fitness.

<p>Fitness results for the base HEADS and the HEADS-EX instruction set architectures. The HEADS-EX architecture includes features from all six tested feature groups, including fully associative arguments, six registers, direct-matched labels, split-I/O, directional search instructions, the ifx instruction, and conditional mov-head instructions. Each entry shows the median log population mean fitness in the respective environment, with confidence intervals in parentheses. Bold entries indicate significant (, Wilcoxon rank-sum test) deviations.</p

Instruction Glossary.

<p>Description of the instructions used across all tested instruction set architectures. A register name (AX, BX, CX, etc.) or head (IP, FLOW, etc.) surrounded by question marks refers to the default argument used when executed, subject to nop modi_cation. Instructions depicted in <b>bold</b> are in the default Heads instruction set.</p

LABEL Series Architectures Task Success.

<p>Task success results of the LABEL-series instruction set architectures. Each entry shows the median normalized task success in the respective environment, with confidence intervals in parentheses. Bold entries denote significant (, Wilcoxon rank-sum test) deviations.</p

LABEL Instruction Sets Tested.

<p>Marks in each column indicating that the set contains the relevant instruction.</p