OMNEST 6.4 (May 2026)

This release brings major improvements to the simulation kernel's numerical stability, a redesigned WATCH mechanism with full STL container inspection, a pluggable RNG manager, and significant NED editor enhancements including figure rendering, rename refactoring, and new display string features. The Qtenv inspector and the IDE also received substantial usability improvements.

Simulation kernel:

  • Redesigned the WATCH mechanism. WATCH() is now universal: it works for any type, including STL containers (std::vector, std::map, etc.), with full recursive inspection of elements. Specialized macros (WATCH_OBJ, WATCH_PTR, WATCH_VECTOR, WATCH_MAP, and others) are now simple aliases for WATCH(). Another improvement is that map and set containers now show their keys as array indices instead of confusing [0], [1], etc.
  • Improved numerical stability: cStdDev, cHistogram, and all result filters/recorders now use Neumaier (Kahan-Babuska-Neumaier) compensated summation for accumulated sums. Additionally, standard deviation and variance computation was improved using std::fma(). This may cause minor differences in recorded statistics compared to previous versions.
  • Fixed time-weighted result filters (timeavg, sumPerDuration, mean in time-weighted mode) ignoring the last interval (from the last emit to simulation end). They now yield the same result as the corresponding recorders.
  • Added RateAverageFilter and RateAverageRecorder ("rateavg" signal statistic) for backward-sample-hold time-weighted averaging, useful for computing average throughput, bitrate, or packet rate.
  • Added pluggable RNG manager mechanism: new cIRngManager interface and cRngManager default implementation. The RNG manager is accessible via cSimulation::getRngManager(). cComponent::getNumRNGs() was also added.
  • cPar: Added unparse() method. Unlike str(), unparse() produces a faithful, parseable representation of the parameter value. str() may now format quantities in the best measurement unit for display purposes.
  • opp_component_ptr: Added resolveFromPar(), resolveFromParOptional(), resolveFromGate(), resolveFromGateOptional() methods for resolving module references from string parameters or by following the connection path.
  • cException, cTerminationException, cRuntimeError: Added experimental support for C++20 std::format-style formatting via the _fmt literal suffix. Example: cRuntimeError("value is {}, name is {}"_fmt, 42, name). Note: OMNeT++ itself does not yet require C++20.
  • cException: prependMessage() changed to take a printf-style format string (was plain text), and no longer automatically inserts ": ". Added appendMessage().
  • Enter_Method() now logs the call with TRACE loglevel.
  • Changed the default precision of result files from 14 to 17 significant digits, which allows a subsequent read operation to recover the value without any precision loss (fix #1464).
  • cChannel::str() no longer includes built-in parameters with default values.
  • UnitConversion: Units may now contain underscores (#1480), e.g. J_K for J/K and m2 for square meter. As a side effect, concatenated units like 1s200ms must now be written as 1s 200ms.
  • Stack trace is now printed on simulation errors when debug-on-errors is enabled but no debugger is present and attaching a debugger is disabled.

NED:

  • Added pyeval() and pycode() NED functions for evaluating Python expressions and executing Python code from NED.
  • Expression evaluation: The / (division) operator now returns integer when both operands are integers and the division is exact.
  • DatarateChannel statistics renamed for clarity: throughput -> averageThroughput, utilization -> averageUtilization.

Display Strings:

  • Implemented support for L-shaped connections via the enhanced m=<srcDir>,<destDir> display string tag, where each endpoint can independently specify horizontal or vertical routing direction.
  • Added support for icon transformations via the new it display string tag. Module icons can now be rotated, flipped, and scaled.
  • Added support for the cring (centered ring) submodule arrangement, where the coordinates specify the center of the ring instead of the bounding rectangle's top-left corner.
  • The row and column arrangements now support optional wrapping.

Cmdenv:

  • Memory Usage Display: The periodic status updates in Express mode now include the memory usage of the process. The displayed value is RSS (Resident Set Size), which represents the portion of memory held in RAM.

Qtenv:

  • Generic Object Inspector: Major redesign for improved usability. Each object now automatically appears in its preferred display mode (Children or Details), eliminating the need for frequent toolbar mode-switching. A small overlay icon on hovered tree rows allows toggling between modes. Added a "Sort by Name" toolbar button for finding specific fields in large objects.
  • Object Tree: Improved synchronization with the graphical module view. Entering a module highlights it in the tree; clicking a submodule highlights it. Added "Show in Graphical View" context menu item. Fixed the tree losing selection and collapsing expanded nodes after each refresh.
  • Added "Distribute Connection Arrows" feature (Ctrl+T toggle). Parallel connections between module pairs are now shifted so they are not drawn on top of each other. The connection line drawing algorithm was also reworked.
  • Added "Reset Zoom" context menu item to the graphical module view.
  • Added "Go to Module" action (Ctrl+G) for quickly navigating to any module.
  • Refined connection tooltips with a compact one-line format and verbose mode showing all hops. Added "Go to Connection Path Start/End" context menu action. Improved mouse picking of bidirectional connections.
  • Run Selection Dialog: Runs are now filterable by typing in the combo box.
  • Log Inspector: Added "Show Messages/Packets Between These Modules" action to the Module Inspector context menu. The module filter is now remembered per module type.
  • Log Inspector: Ctrl+A "Select All" now works in the embedded log view.
  • Preferences: Made the log prefix format an editable combobox with predefined format options. Removed two obsolete checkboxes that had no effect.
  • Similarly to Cmdenv, Qtenv now displays the memory usage (RSS) of the process in the status bar at the bottom.
  • Fix: Ensured the Stop dialog is modal on macOS.
  • Fixed Log Inspector column width corruption when switching between Log and Messages modes.

Command-line Tools:

  • opp_fingerprinttest: Major overhaul. New options: -f/-F (filter/exclude by fingerprint ingredient type), --show-passed, --show-runtime, -c/--calculator, -q/--disable_outfile, -s/--release, -n/-i (test case splitting), -l/--logfile. Added fingerprint group support, colored output, tags field in CSV parsing, and improved error handling.
  • opp_scavetool: Fixed unnecessary stddev recomputation (#1465).
  • opp_test: Added %round-numbers directive.

NED Editor:

  • Added canvas @figure rendering and editing support in the graphical NED editor. Figures defined as @figure properties in NED are now displayed and can be interacted with visually. Supported figure types include rectangle, oval, ring, arc, pieslice, path, polygon, polyline, label, text, icon, image, and pixmap. Figures can be moved, resized, copied and pasted (including figure hierarchies), and their properties can be edited via the Properties view.
  • Added rename refactoring with preview and undo/redo support for NED types, submodules, gates, and parameters. Renames are propagated across NED, INI, and C++ files.
  • Added support for editing icon transformation (it display string tag), centered ring arrangement (cring), L-shaped connection routing, and layout group (g tag) in the graphical editor and Properties dialog.
  • Hover tooltips now show "inherited from ..." for inherited submodules, connections, and figures. A new "Go to Definition" context menu action navigates to the base type.
  • Added validation that modules and channels fulfill their declared interface contracts (matching parameters and gates with correct types and attributes).
  • Added missing property types (@figure, @omittedTypename, @reconnect, @defaultname, @mutable, @class, @loose, @directIn) to autocomplete suggestions.
  • Added quick type hierarchy popup (Ctrl+T) in the textual NED editor.
  • Added "Spread Connection Arrows" context menu option.
  • Several bug fixes including crashes from stale async messages, snap-to-grid initialization, and fixes for inherited @figure properties.

Other IDE Components:

  • Project Installer: Numerous improvements to the Install Simulation Models dialog. The installer now automatically sets up build configurations, environment variables, project references, and can apply file substitutions. Project dependencies are validated before installation.
  • NED Documentation Generator: Removed mobile view. Fixed layout glitch at certain zoom levels. The navigation panel width now persists between page reloads.
  • Fixed spurious deadlock detection dialogs in the IDE caused by cumulative blocking time tracking.
  • Ini File Editor: Fixed a deadlock between the analyzer and the Eclipse job manager.
  • MSG Editor: Added Ctrl+Tab shortcut to switch to the generated header file.
  • Updated the bundled Eclipse platform to 2026-03, PyDev to 13.1.0, and JDK to version 25 LTS.

Python library:

  • omnetpp.scave: Improved compatibility with Pandas 3.0 and NumPy 2.0.

Build:

  • Added NixOS support: install.sh now works on NixOS, setenv can be sourced on NixOS. Added .opp_shell/flake.nix for Nix development shell support.
  • Fixed incorrect clang toolchain name on macOS with newer (22.0+) clang versions.
  • Various build fixes for macOS and Windows.

See ChangeLogs in individual folders for details.

Bugs fixed: https://github.com/omnetpp/omnetpp/issues?q=is%3Aissue+is%3Aclosed+milestone%3A6.4


What's New in OMNEST 6.3.0