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### 2 Changes between GAP 4.8 and GAP 4.9

This chapter contains an overview of the most important changes introduced in GAP 4.9.1 release (the 1st public release of GAP 4.9). Later it will also contain information about subsequent update releases for GAP 4.9.

These changes are also listed on the Wiki page https://github.com/gap-system/GAP/wiki/gap-4.9-release-notes.

#### 2.1 GAP 4.9.1 (May 2018)

##### 2.1-1 Changes in the core GAP system introduced in GAP 4.9

Major changes:

• Merged HPC-GAP into GAP. For details, please refer to Subsection 2.1-2 at the end of these release notes.

• GAP has a new build system, which resolves many quirks and issues with the old system, and will be easier to maintain. For regular users, the usual ./configure && make should work fine as before. If you are interested in technical details on the new build system, take a look at README.buildsys.md.

• The guidelines for developing GAP packages were revised and moved from the Example package to Reference: Using and Developing GAP Packages (#484).

• In addition to supporting single argument lambda functions like a -> a+1, GAP now supports lambdas with fewer or more than one argument, or even a variable number. E.g. {a,b} -> a+b is a shorthand for function(a,b) return a+b; end. For details on how to use this, see Reference: Function. For technical details, e.g. why we did not choose the syntax (a,b) -> a+b, see #490.

• Function calls, list accesses and records accesses now can be nested. For example, you can now write y := f().x; (essentially equivalent to y := f();; y := y.x;), which previously would have resulted in an error; see #457 and #462).

• The libraries of small, primitive and transitive groups which previously were an integral part of GAP were split into three separate packages PrimgGrp, SmallGrp and TransGrp. For backwards compatibility, these are required packages in GAP 4.9 (i.e., GAP will not start without them). We plan to change this for GAP 4.10 (see #2434), once all packages which currently implicitly rely on these new packages had time to add explicit dependencies on them (#1650, #1714).

• The performance of GAP's sorting functions (such as Sort (Reference: Sort), SortParallel (Reference: SortParallel), etc.) has been substantially improved, in some examples by more than a factor of four: as a trivial example, compare the timing for Sort([1..100000000] * 0). As a side effect, the result of sorting lists with equal entries may produce different answers compared to previous GAP versions. If you would like to make your code independant of the exact employed sorting algorithm, you can use the newly added StableSort (Reference: StableSort), StableSortBy (Reference: StableSortBy) and StableSortParallel (Reference: StableSortParallel). (For some technical details, see #609).

• We removed our old home-grown big integer code, and instead always use the GMP based big integer code. This means that the GMP library now is a required dependency, not just an optional one. Note that GAP has been using GMP big integer arithmetic for a long time by default, and we also have been bundling GMP with GAP. So this change mostly removed code that was never in use for most users.

• A number of improvements have been made to Random (Reference: Random). These may lead to different sequences of numbers being created. On the up side, many more methods for Random (Reference: Random) (and other RandomXYZ operations) now optionally take an explicit RandomSource (Reference: RandomSource) as first argument (but not yet all: help with issue #1098 is welcome). Some relevant pull requests:

• Allow creating random permutations using a random source (#1165)

• Let more Random (Reference: Random) methods use an alternative source (#1168)

• Help Random (Reference: Random) methods to use RandomSource (Reference: RandomSource) (#810)

• Remove uses of old random generator (#808)

• Fix Random (Reference: Random) on long (>2^28) lists (#781)

• Fix RandomUnimodularMat (Reference: RandomUnimodularMat) (#1511)

• Use RandomSource (Reference: RandomSource) in a few more places (#1599)

• The output and behaviour of the profiling system has been substantially improved:

• Make profiling correctly handle the same file being opened multiple times (#1069)

• Do not profile the return statements (Reference: return) inserted into the end of functions (#1073)

• Ensure we reset OutputtedFilenameList in profiling when a workspace is restored (#1164)

• Better tracking of amounts of memory allocated and time spent in the garbage collector (#1806)

• Allow profiling of memory usage (#1808)

• Remove profiling limit on files with <= 2^16 lines (#1913)

• In many cases GAP now outputs the filename and location of functions in helpful places, e.g. in error messages or when displaying compiled functions. We also try to always use the format FILENAME:LINE, which various utilities already know how to parse (e.g. in iTerm2, cmd-clicking on such a string can be configured to open an editor for the file at the indicated line). For some technical details, see #469, #755, #1058.

• GAP now supports constant variables, whose value cannot change anymore during runtime; code using such constants can then be slightly optimized by GAP. E.g. if foo is turned into a constant variable bound to the value false, then GAP can optimize if foo then ... fi; blocks completely away. For details, see MakeConstantGlobal (Reference: MakeConstantGlobal) in Reference: More About Global Variables. (#1682, #1770)

Other changes:

• Enhance StructureDescription (Reference: StructureDescription) with a major rewrite, enhancing DirectFactorsOfGroup" and adding SemidirectDecompositions; the core algorithm now also works for infinite abelian groups. Further, it became faster by quickly finding abelian direct factors and recognizing several cases where the group is direct indecomposable. (#379, #763, #985)

• Mark FittingSubgroup (Reference: FittingSubgroup) and FrattiniSubgroup (Reference: FrattiniSubgroup) as nilpotent (#400)

• Add method for Socle (Reference: Socle) for finite nilpotent groups (#402)

• Change ViewString (Reference: ViewString) and String (Reference: String) methods for various inverse semigroups and monoids (#438, #880, #882)

• Enhance some nilpotent and p-group attributes (#442)

• Improve Union (Reference: Union) for a list with many ranges (#444)

• Add UserHomeExpand (Reference: UserHomeExpand), a function to expand ~ in filenames. (#447)

• Extra hint in "No Method Found" error message if one of the arguments is fail (#460)

• Tell Sylow subgroups of natural A_n or S_n their size when we make them (#529)

• Some small enhancements on Sylow and Hall subgroup computations, mostly for nilpotent groups. (#535)

• Remove .zoo archive related tools (#540)

• Add new FrattiniSubgroup (Reference: FrattiniSubgroup), MaximalNormalSubgroups (Reference: MaximalNormalSubgroups), MinimalNormalSubgroups (Reference: MinimalNormalSubgroups) and Socle (Reference: Socle) methods for abelian and/or solvable groups, even infinite ones. The new methods are only triggered if the group already knows that it is abelian and/or solvable. (#552, #583, #606)

• New attribute NormalHallSubgroups, returning a list of all normal Hall subgroups of a group. (#561)

• Add ComplementClassesRepresentatives (Reference: ComplementClassesRepresentatives) fallback method for arbitrary groups (#563)

• (#612) Add parsing of hex literals in strings, e.g. "\0x61" is turned into "a" (#612)

• Collection of enhancements (#683)

• Various speed improvements to polynomial factorisation and the GAP MeatAxe (#720, #1027)

• The code and documentation for transformations is improved and corrected in many instances (#727, #732)

• Change RootFFE to optionally takes a field or field size as first argument, from which the roots will be taken (#761)

• Change Permanent (Reference: Permanent) from a global function to an attribute (#777)

• Add CallFuncListWrap (Reference: CallFuncListWrap) to wrap return value to allow distinguishing between functions which return and functions which don't (#824)

• Allow repeated use of same DeclareSynonym (Reference: DeclareSynonym) call (#835)

• New implementation of modified Todd-Coxeter (the old one had bugs, see #302), #843)

• New functionality: Cannon/Holt automorphisms and others (#878)

• Add IsPowerfulPGroup (Reference: IsPowerfulPGroup) property, and a FrattiniSubgroup (Reference: FrattiniSubgroup) method for powerful p-groups (#894)

• Improve performance for group isomorphism/automorphisms (#896, #968)

• Make ListX (Reference: ListX), SetX (Reference: SetX), SumX (Reference: SumX) and ProductX (Reference: ProductX) support lists which are not collections (#903)

• Some improvements for LatticeByCyclicExtension (Reference: LatticeByCyclicExtension) (#905)

• Add helpers to retrieve information about operations and filters: CategoryByName (Reference: CategoryByName), TypeOfOperation (Reference: TypeOfOperation), FilterByName (Reference: FilterByName), FiltersObj (Reference: FiltersObj), FiltersType (Reference: FiltersType), IdOfFilter, IdOfFilterByName, IsAttribute (Reference: IsAttribute), IsCategory (Reference: IsCategory), IsProperty (Reference: IsProperty), IsRepresentation (Reference: IsRepresentation) (#925, #1593)

• Give better error message if a help file is missing (#939)

• Add LowercaseChar (Reference: LowercaseChar) and UppercaseChar (Reference: UppercaseChar) (#952)

• Add PositionMaximum (Reference: PositionMaximum) and PositionMinimum (Reference: PositionMinimum) (#956)

• Switching default command history length from infinity to 1000 (#960)

• Allow conversion of -infinity to float via NewFloat (Reference: NewFloat) and MakeFloat (Reference: MakeFloat) (#961)

• Add option NoPrecomputedData to avoid use of data libraries in certain computations (useful if one wants to verify the content of these data libraries) (#986)

• Remove one-argument version of AsPartialPerm (Reference: AsPartialPerm for a permutation and a set of positive integers) for a transformation (#1036)

• Partial perms now have a MultiplicativeZero (Reference: MultiplicativeZero) rather than a Zero (Reference: Zero), since they are multiplicative rather than additive elements (#1040)

• Various enhancements: (#1046)

• A bugfix in NaturalHomomorphismByIdeal (Reference: NaturalHomomorphismByIdeal) for polynomial rings

• Improvements in handling solvable permutation groups

• The trivial group now is a member of the perfect groups library

• Improvements in using tabulated data for maximal subgroups

• New tests for group constructors and some fixes (e.g. GO(1,4,5) used to trigger an error) (#1053)

• Make HasSolvableFactorGroup slightly more efficient (#1062)

• Enhance HasXXFactorGroup (#1066)

• Remove GAP4stones from tests (#1072)

• AsMonoid (Reference: AsMonoid) and AsSemigroup (Reference: AsSemigroup) are now operations, and various bugs were resolved related to isomorphisms of semigroups and monoids (#1112)

• Mark isomorphisms between trivial groups as bijective (#1116)

• Speed up RootMod (Reference: RootMod) and RootsMod (Reference: RootsMod) for moduli with large prime factors; also add IS_PROBAB_PRIME_INT kernel function (#1141)

• The search for the documentation of system setters and testers now returns corresponding attributes and properties (#1144)

• Remove command line options -c, -U, -i and -X, add --quitonbreak (#1192, #1265, #1421, #1448)

• Remove Itanium support (#1163)

• Adding two strings now shows a more helpful error message (#1314)

• Suppress Unbound global variable warning in IsBound (Reference: IsBound for a global variable) (#1334)

• Increase warning level for Conway polynomial (#1363)

• Performance improvements to maximal and intermediate subgroups, fix of RepresentativeAction (Reference: RepresentativeAction) (#1390)

• Revise Chapter 52 of the reference manual (fp semigroups and monoids) (#1441)

• Improve the performance of the Info (Reference: Info) statement (#1464, #1770)

• When printing function bodies, avoid some redundant spaces (#1498)

• Add kernel functions for directly accessing entries of GF2/8bit compressed matrices (#1585)

• Add String (Reference: String) method for functions (#1591)

• Check modules were compiled with the same version of GAP when loading them (#1600)

• When printing function, reproduce TryNextMethod() correctly (#1613)

• New "Bitfields" feature (Reference: Bitfields) providing efficient support for packing multiple data items into a single word for cache and memory efficiency (#1616)

• Improved bin/BuildPackages.sh, in particular added option to abort upon failure (#2022)

• Rewrote integer code (GMP) for better performance of certain large integer operations, and added kernel implementations of various functions, including these:

• Add kernel implementations of AbsInt (Reference: AbsInt), SignInt (Reference: SignInt); add new kernel functions ABS_RAT, SIGN_RAT; and speed up Reference: mod, RemInt (Reference: RemInt), QuoInt (Reference: QuoInt) for divisors which are small powers of 2 (#1045)

• Add kernel implementations of Jacobi (Reference: Jacobi), PowerModInt (Reference: PowerModInt), Valuation (Reference: Valuation) (for integers), PValuation (Reference: PValuation) (for integers) (#1075)

• Add kernel implementation of Factorial (Reference: Factorial) (#1969)

• Add kernel implementation of Binomial (Reference: Binomial) (#1921)

• Add kernel implementation of LcmInt (Reference: LcmInt) (#2019)

• Check version of kernel for package versions (#1600)

• Add new AlgebraicExtensionNC (Reference: AlgebraicExtensionNC) operation (#1665)

• Add NumberColumns and NumberRows to MatrixObj interface (#1657)

• MinimalGeneratingSet (Reference: MinimalGeneratingSet) returns an answer for non-cyclic groups that already have a generating set of size 2 (which hence is minimal) (#1755)

• Add GetWithDefault (Reference: GetWithDefault) which returns the n-th element of the list if it is bound, and the default value otherwise (#1762)

• Fast method for ElmsBlist when positions are a range with increment 1 (#1773)

• Make permutations remember their inverses (#1831)

• Add invariant forms for GU(1,q) and SU(1,q) (#1874)

• Implement StandardAssociate (Reference: StandardAssociate) and StandardAssociateUnit (Reference: StandardAssociateUnit) for ZmodnZ (Reference: ZmodnZ), clarify documentation for IsEuclideanRing (Reference: IsEuclideanRing) (#1990)

• Improve documentation and interface for floats (#2016)

• Add PositionsProperty (Reference: PositionsProperty) method for non-dense lists (#2021)

• Add TrivialGroup(IsFpGroup) (#2037)

• Change ObjectifyWithAttributes (Reference: ObjectifyWithAttributes) to return the new objects (#2098)

• Removed a never released undocumented HPC-GAP syntax extension which allowed to use a backtick/backquote as alias for MakeImmutable (Reference: MakeImmutable). (#2202).

• Various changes (#2253):

• Improve performance and memory usage of ImageKernelBlocksHomomorphism"

• Document LowIndexSubgroups (Reference: LowIndexSubgroups)

• Correct ClassesSolvableGroup (Reference: ClassesSolvableGroup) documentation to clarify that it requires, but does not test membership

• fix IsNaturalGL (Reference: IsNaturalGL) for trivial matrix groups with empty generating set

• Make it possible to interrupt repeat continue; until false; and similar tight loops with "Ctrl-C" (#2259).

• Improved GAP testing infrastructure, extended GAP test suite, and increased code coverage

• Countless other tweaks, improvements, fixes were applied to the GAP library, kernel and manual

Fixed bugs:

• Fix bugs in NormalSubgroups (Reference: NormalSubgroups) and PrintCSV (Reference: PrintCSV) (#433)

• Fix nice monomorphism dispatch for HallSubgroup (Reference: HallSubgroup) (e.g. fixes HallSubgroup(GL(3,4), [2,3])) (#559)

• Check for permutations whose degree would exceed the internal limit, and document that limit (#581)

• Fix segfault after quitting from the break loop in certain cases (#709 which fixes #397)

• Fix rankings for Socle (Reference: Socle) and MinimalNormalSubgroups (Reference: MinimalNormalSubgroups) (#711)

• Make key and attribute values immutable (#714)

• Make OnTuples([-1], (1,2)) return an error (#718)

• Fix bug in NewmanInfinityCriterion (Reference: NewmanInfinityCriterion) which could corrupt the PCentralSeries (Reference: PCentralSeries) attribute (#719)

• The length of the list returned by OnSetsPerm is now properly set (#731)

• Fix Remove (Reference: Remove) misbehaving when last member of list with gaps in it is removed (#766)

• Fix bugs in various methods for Rees (0-)matrix semigroups: IsFinite (Reference: IsFinite), IsOne (Reference: IsOne), Enumerator (Reference: Enumerator), IsReesMatrixSemigroup (Reference: IsReesMatrixSemigroup) and IsReesZeroMatrixSemigroup (Reference: IsReesZeroMatrixSemigroup) (#768, #1676)

• Fix IsFullTransformationSemigroup (Reference: IsFullTransformationSemigroup) to work correctly for the full transformation semigroup of degree 0 (#769)

• Fix printing very large (> 2^28 points) permutations (#782)

• Fix Intersection([]) (#854)

• Fix crash in IsKernelFunction for some inputs (#876)

• Fix bug in ShortestVectors (Reference: ShortestVectors) which could cause OrthogonalEmbeddings (Reference: OrthogonalEmbeddings) to enter a break loop (#941)

• Fix crash in some methods involving partial perms (#948)

• FreeMonoid(0) no longer satisfies IsGroup (Reference: IsGroup) (#950)

• Fix crash when invoking weak pointer functions on invalid arguments (#1009)

• Fix a bug parsing character constants (#1015)

• Fix several bugs and crashes in Z(p,d) for invalid arguments, e.g. Z(4,5), Z(6,3) (#1029, #1059, #1383, #1573)

• Fix starting GAP on systems with large inodes (#1033)

• Fix NrFixedPoints (Reference: NrFixedPoints for a partial perm) and FixedPointsOfPartialPerm (Reference: FixedPointsOfPartialPerm for a partial perm) for a partial perm and a partial perm semigroup (they used to return the moved points rather than the fixed points) (#1034)

• Fix MeetOfPartialPerms (Reference: MeetOfPartialPerms) when given a collection of 1 or 0 partial perms (#1035)

• The behaviour of AsPartialPerm (Reference: AsPartialPerm for a transformation and a set of positive integer) for a transformation and a list is corrected (#1036)

• IsomorphismReesZeroMatrixSemigroup (Reference: IsomorphismReesZeroMatrixSemigroup) for a 0-simple semigroup is now defined on the zero of the source and range semigroups (#1038)

• Fix isomorphisms from finitely-presented monoids to finitely-presented semigroups, and allow isomorphisms from semigroups to fp-monoids (#1039)

• Fix One (Reference: One) for a partial permutation semigroup without generators (#1040)

• Fix MemoryUsage (Reference: MemoryUsage) for positional and component objects (#1044)

• Fix PlainString causing immutable strings to become mutable (#1096)

• Restore support for sparc64 (#1124)

• Fix a problem with < for transformations, which could give incorrect results (#1130)

• Fix crash when comparing recursive data structures such as [~] = [~] (#1151)

• Ensure output of TrivialGroup(IsPermGroup) has zero generators (#1247)

• Fix for applying the InverseGeneralMapping (Reference: InverseGeneralMapping) of an IsomorphismFpSemigroup (Reference: IsomorphismFpSemigroup) (#1259)

• Collection of improvements and fixes: (#1294)

• A fix for quotient rings of rings by structure constants

• Generic routine for transformation matrix to rational canonical form

• Speed improvements to block homomorphisms

• New routines for conjugates or subgroups with desired containment

• Performance improvement for conjugacy classes in groups with a huge number of classes, giving significant improvements to IntermediateSubgroups (Reference: IntermediateSubgroups) (e.g. 7-Sylow subgroup in PSL(7,2)), ascending chain and thus in turn double coset calculations and further routines that rely on it

• Fix EqFloat (Reference: EqFloat) to return correct results, instead of always returning false (#1370)

• Various changes, including fixes for CallFuncList (Reference: CallFuncList) (#1417)

• Better define the result of MappingPermListList (Reference: MappingPermListList) (#1432)

• Check the arguments to IsInjectiveListTrans (Reference: IsInjectiveListTrans) to prevent crashes (#1435)

• Change BlownUpMat (Reference: BlownUpMat) to return fail for certain invalid inputs (#1488)

• Fixes for creating Green's classes of semigroups (#1492, #1771)

• Fix DoImmutableMatrix for finite fields (#1504)

• Make structural copy handle boolean lists properly (#1514)

• Minimal fix for algebraic extensions over finite fields of order > 256 (#1569)

• Fix for computing quotients of certain algebra modules (#1669)

• Fix an error in the default method for PositionNot (Reference: PositionNot) (#1672)

• Improvements to Rees matrix semigroups code and new tests (#1676)

• Fix CodePcGroup (Reference: CodePcGroup) for the trivial polycyclic group (#1679)

• Fix FroidurePinExtendedAlg for partial permutation monoids (#1697)

• Fix computing the radical of a zero dimensional associative algebra (#1701)

• Fix a bug in RadicalOfAlgebra (Reference: RadicalOfAlgebra) which could cause a break loop for some associative algebras (#1716)

• Fix a recursion depth trap error when repeatedly calling Test (Reference: Test) (#1753)

• Fix bugs in PrimePGroup (Reference: PrimePGroup) for direct products of p-groups (#1754)

• Fix UpEnv (Reference: UpEnv) (available in break loops) when at the bottom of the backtrace (#1780)

• Fix IsomorphismPartialPermSemigroup (Reference: IsomorphismPartialPermSemigroup) and IsomorphismPartialPermMonoid (Reference: IsomorphismPartialPermMonoid) for permutation groups with 0 generators (#1784)

• Fix DisplaySemigroup (Reference: DisplaySemigroup) for transformation semigroups (#1785)

• Fix "no method found" errors in MagmaWithOne (Reference: MagmaWithOne) and MagmaWithInverses (Reference: MagmaWithInverses) (#1798)

• Fix an error computing kernel of group homomorphism from fp group into permutation group (#1809)

• Fix an error in MTC losing components when copying a new augmented coset table (#1809)

• Fix output of Where (Reference: Where) in a break loop, which pointed at the wrong code line in some cases (#1814)

• Fix the interaction of signals in GAP and the IO package (#1851)

• Make line editing resilient to LineEditKeyHandler failure (in particular, don't crash) (#1856)

• Omit non-characters from PermChars (Reference: PermChars) results (#1867)

• Fix ExteriorPower (Reference: ExteriorPowerOfAlgebraModule) when exterior power is 0-dimensional (used to return a 1-dimensional result) (#1872)

• Fix recursion depth trap and other improvements for quotients of fp groups (#1884)

• Fix a bug in the computation of a permutation group isomorphic to a group of automorphisms (#1907)

• Fix bug in InstallFlushableValueFromFunction (Reference: InstallFlushableValueFromFunction) (#1920)

• Fix ONanScottType (Reference: ONanScottType) and introduce RestrictedInverseGeneralMapping (Reference: RestrictedInverseGeneralMapping) (#1937)

• Fix QuotientMod (Reference: QuotientMod) documentation, and the integer implementation. This partially reverts changes made in version 4.7.8 in 2013. The documentation is now correct (resp. consistent again), and several corner cases, e.g. QuotientMod(0,0,m) now work correctly (#1991)

• Fix PositionProperty (Reference: PositionProperty) with from < 1 (#2056)

• Fix inefficiency when dealing with certain algebra modules (#2058)

• Restrict capacity of plain lists to 2^28 in 32-bit and 2^60 in 64-bit builds (#2064)

• Fix crashes with very large heaps (> 2 GB) on 32 bit systems, and work around a bug in memmove in 32-bit glibc versions which could corrupt memory (affects most current Linux distributions) (#2166).

• Fix name of the reversed option in documentation of LoadAllPackages (Reference: LoadAllPackages) (#2167).

• Fix TriangulizedMat([]) (see TriangulizedMat (Reference: TriangulizedMat) to return an empty list instead of producing an error (#2260).

• Fix several potential (albeit rare) crashes related to garbage collection (#2321, #2313, #2320).

Removed or obsolete functionality:

• Make SetUserPreferences obsolete (use SetUserPreference (Reference: SetUserPreference) instead) (#512)

• Remove undocumented NameIsomorphismClass (#597)

• Remove unused code for rational classes of permutation groups (#886)

• Remove unused and undocumented Randomizer and CheapRandomizer (#1113)

• Remove install-tools.sh script and documentation mentioning it (#1305)

• Withdraw CallWithTimeout and CallWithTimeoutList (#1324)

• Make RecFields obsolete (use RecNames (Reference: RecNames) instead) (#1331)

• Remove undocumented SuPeRfail and READ_COMMAND (#1374)

• Remove unused oldmatint.gi (old methods for functions that compute Hermite and Smith normal forms of integer matrices) (#1765)

• Make TRANSDEGREES obsolete (#1852)

##### 2.1-2 HPC-GAP

GAP includes experimental code to support multithreaded programming in GAP, dubbed HPC-GAP (where HPC stands for "high performance computing"). GAP and HPC-GAP codebases diverged during the project, and we are currently working on unifying the codebases and incorporating the HPC-GAP code back into the mainstream GAP versions.

This is work in progress, and HPC-GAP as it is included with GAP right now still suffers from various limitations and problems, which we are actively working on to resolve. However, including it with GAP (disabled by default) considerably simplifies development of HPC-GAP. It also means that you can very easily get a (rough!) sneak peak of HPC-GAP. It comes together with the new manual book called "HPC-GAP Reference Manual" and located in the doc/hpc directory.

Users interested in experimenting with shared memory parallel programming in GAP can build HPC-GAP by following the instructions from https://github.com/gap-system/gap/wiki/Building-HPC-GAP. While it is possible to build HPC-GAP from a release version of GAP you downloaded from the GAP website, due to the ongoing development of HPC-GAP, we recommend that you instead build HPC-GAP from the latest development version available in the GAP repository at GitHub, i.e. https://github.com/gap-system/gap.

##### 2.1-3 New and updated packages since GAP 4.8.10

There were 132 packages redistributed together with GAP 4.8.10. The GAP 4.9.1 distribution includes 134 packages, including numerous updates of previously redistributed packages, and some major changes outlined below.

The libraries of small, primitive and transitive groups which previously were an integral part of GAP were split into three separate packages PrimgGrp, SmallGrp and TransGrp:

• The PrimGrp package by Alexander Hulpke, Colva M. Roney-Dougal and Christopher Russell provides the library of primitive permutation groups which includes, up to permutation isomorphism (i.e., up to conjugacy in the corresponding symmetric group), all primitive permutation groups of degree < 4096.

• The SmallGrp package by Bettina Eick, Hans Ulrich Besche and Eamonn O’Brien provides the library of groups of certain "small" orders. The groups are sorted by their orders and they are listed up to isomorphism; that is, for each of the available orders a complete and irredundant list of isomorphism type representatives of groups is given.

• The TransGrp package by Alexander Hulpke provides the library of transitive groups, with an optional download of the library of transitive groups of degree 32.

For backwards compatibility, these are required packages in GAP 4.9 (i.e., GAP will not start without them). We plan to change this for GAP 4.10 (see #2434), once all packages which currently implicitly rely on these new packages had time to add explicit dependencies on them (#1650, #1714).

The new ZeroMQInterface package by Markus Pfeiffer and Reimer Behrends has been added for the redistribution. It provides both low-level bindings as well as some higher level interfaces for the ZeroMQ message passing library for GAP and HPC-GAP enabling lightweight distributed computation.

The HAPprime package by Paul Smith is no longer redistributed with GAP. Part of the code has been incorporated into the HAP package. Its source code repository, containing the code of the last distributed version, can still be found at https://github.com/gap-packages/happrime.

Also, the ParGAP package by Gene Cooperman is no longer redistributed with GAP because it no longer can be compiled with GAP 4.9 (see this announcement). Its source code repository, containing the code of the last distributed version, plus some first fixes needed for compatibility for GAP 4.9, can still be found at https://github.com/gap-packages/pargap. If somebody is interested in repairing this package and taking over its maintenance, so that it can be distributed again, please contact the GAP team.

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