Ymer 4.3 (Jan 9, 2019)

• Replace support for distributed sampling with support for multi-threaded sampling.
• Provide more statistics on sample path lengths in output.
• Use distinct tokens for non-exponential distributions (@W, @l, @U) so as not to clash with legal identifiers in the PRISM language.
• Fix compilation of properties with labels.
• Ensure optimization does not reorder operations in compiled expressions.
• When path logging is enabled, make sure the last state is always logged.
• Fix build issues with newer versions of clang and gcc.

Ymer 4.2.1 (Apr 30, 2015)

• Fixed bug in computation of required registers for evaluation compiled expressions, which was ignoring pivoted compiled commands.
• Fixed bug in sampling engine when verifying unbounded path properties, which resulted in early termination of sample paths never to trigger properly.

Ymer 4.2 (Apr 21, 2015)

• Support multiple initial states for the hybrid engine.
• New optimized instructions for comparing variable and constant value.
• Added missing optimization of composed guards in compiled model.
• Fixed bug in expression optimization that resulted in incorrect constant folding in some cases.

Ymer 4.1 (Mar 14, 2015)

• Support for formulas and labels.
• Support for eventually (F) path operator.
• Support for Pr=?[...] properties.
• Support for unbounded until with sampling engine using weighted sampling.
• Parser support for init state expressions and system specifications.
• Fixed bug in compilation of updates for variables of type bool.

Ymer 3.2 (Jan 25, 2015)

• Support for DTMC model checking with sampling engine.
• Support for unbounded until properties with mixed engine.
• Support for variables of type bool.
• Support for complex constant expressions.
• New simulator that works directly with a factored event model, so that synchronized events do not have to be resoved up front, which can otherwise result in event explosion.
• Improved model optimization for simulation.
• Fixed bug in synchronization for actions with commands in more than two modules.

Ymer 3.1 (Nov 14, 2014)

• Expression and property compilation, resulting in 5-25% speedup on select benchmarks.
• More efficient representation of non-memoryless trigger times in a simulation state.
• Switched to fixed-width sequential confidence intervals for probability estimation.
• Changed name of single sampling plan algorithm to SSP from SEQUENTIAL.
• Switched to simple heuristic for picking nested error bounds for probabilistic properties.
• Improved support for PRISM expressions, including function calls and conditional expressions.
• Fixed bug in error bounds for conjunction, disjunction, and nested probabilistic properties.
• Code now uses C++11 language features.

Ymer 3.0.5.1 (Nov 10, 2014)

• Back port fix for memory corruption bug in parser.

Ymer 3.0.9 (Jun 2, 2012)

• More efficient representation for variable assignments in a state. Up to 36% speedup on polling benchmarks.

Ymer 3.0.8 (May 4, 2012)

• Fixed memory corruption bug in parser.
• Fixed test breakage when using GCC 4.2.

Ymer 3.0.7 (Apr 14, 2012)

• Fixed bug in parsing of constant overrides introduced in version 3.0.6, where all constant overrides would be given the value 1. The actual speedup over version 3.0.5, with the bug fixed, is 10-15% on benchmarks.
• Fixed long-standing memory leak in hybrid engine.