v4.3.2 (February 6, 2020)
• Up to 64 parallel tasks (instead of 48).

v4.3.1 (April 28, 2019)
Assembler code improvements (Primo should be slightly faster with big numbers).

v4.3.0 (February 21, 2018)
• Maximal size of candidates increased up to 132,928 bits (~ 40,000 decimal digits).
• Modified the phase 1 strategy. There are now three possible passes (due to this modification, the binary format of the .t files was modified making impossible to resume a certification started with a previous version of Primo). The goal was to produce smaller certificates that are slightly faster to check.
• Modified the phase 2 strategy. The tests are now sorted in order to improve the parallelization.
• Modified the Setup dialog box.
• Modified the primo.ini file structure.
• Modified the primo.html help file.
• Added data in order to speed a little up polynomial factorizations.
• Suppressed the certification report generation (i.e., no more .cr files).
• Suppressed the cumbersome and useless extended factorization stuff.
• Fixed a bug that could raise the internal error 4.0.2.1. Thanks to Tom Wu who reported it.
• Fixed bugs that could raise the internal errors 4.21.7.2, 4.19.112.1 and 4.12.15.2. Thanks to Ed Hall who reported them.

v4.2.1 (May 9, 2016)
• Added a CPU Info group box to the Setup dialog box. It indicates the processor name, the number of core(s) and the number of thread(s) per core.
• Fixed a bug that was activated with the discriminant -6173652. Thanks to David Metcalf who reported it.

v4.2.0 (March 3, 2016)
• NEW CERTIFICATE FORMAT.
Since the certificate signature scheme was modified (the previous stuff was too old and not at all adapted to 64-bit processors), things that should have been changed since long were also modified.
• Added a check box to the Verification page. Its associated option allows to update certificates from the old format 3 to the new format 4 (when signing or checking signatures).
• NEW TUNING FOR THE PHASE #1.
The produced certificates contain less tests (on average) and, consequently, their checking is slightly f aster.
• Added a Setup... item to the main menu.
• Modified the Elapsed time chrono for certifications and verifications. It now indicates the whole certification/verification running time. Up to now, it was not the case when aborting/resuming.
• Added new discriminants.
• Added Girstmair polynomial factorization. It speeds a little up the factorization of polynomials having a small degree and a cyclic Galois group.
• Almost all the assembler code parts were rewritten.
• Fixed a bug that could raise the internal error 4.0.2.1. Thanks to Richard Dickerson who reported it.

v4.1.1 (January 4, 2015)
• Maximal size of candidates increased up to 116224 bits (35000 decimal digits).
• Number of possible concurrent tasks increased up to 48.
• Added new discriminants.
• Modified the factorization of polynomials. It now requires a little less memory.
• Added double-eta quotient invariants in order to compute class polynomials with smaller coefficients. (It is almost sure now that the patent WO/2005/004383 will not be granted, at least the claims 1, 2, 3, and 6.)

v4.1.0 (January 4, 2014)
• Fixed a bug concerning the verifier code. The new Primo versions can produce tests of type 3 or 4 with a S value equal to 1 but the verifier code was not updated accordingly. Thanks to Dana Jacobsen who reported it.
• Fixed a cosmetic bug.
• Modified the input file format and the expression parser. See Input file in the Primo help file.
• Modified the backtrack rules.
• Added new discriminants.
• Added an extended sieve stuff.
• Replaced the tkcs, tkc1, tkc2 and tkcv executable files with ptk0, ptk1, ptk2 and ptk3.

v4.0.5 (November 7, 2013)
• Fixed a bug that could raise the internal error 1.17.102.1 during the phase 1.

v4.0.4 (September 15, 2013)
• Fixed a bug that could raise internal errors (1.13.9.7 or 1.17.4.1) during the phase 2. Thanks to Richard Dickerson who reported it.
• More discriminants.
• Sieve Parameters setting modified.
• Sieve code modified (the sieving part should be slightly faster with very big numbers)

v4.0.3 (April 18, 2013)
• Modified the Sieve Parameters setting.
• Updated the help file (Sieve parameters topic).

v4.0.2 (April 2, 2013)
• New discriminant tables.
• New [Running Times] sections: wall-clock time + process time.
• Compiled with a more recent version of the Free Pascal compiler.

v4.0.1 (October 28, 2012)
• Number of possible concurrent tasks increased up to 32.

v4.0.0 - alpha 16 (July 24, 2012)
• Sieve lower bound set to 2²² instead of 2²⁰.
• Slightly faster multiplication (about 10%) with very big numbers.

v4.0.0 - alpha 15 (May 10, 2012)
• Sieve upper bound increased up to 2³².
• Fixed a bug concerning the new class invariants added to v. alpha 13. Thanks to Ed Hall who reported it.
• Minor cosmetic changes.

v4.0.0 - alpha 14 (March 16, 2012)
• Fixed a bug concerning the new class invariants added to v. alpha 13. Due to this bug, a certification could be aborted by Primo (internal error 4.0.2.1) during the so-called Phase 2. Thanks to Frank Schickel who reported it.

v4.0.0 - alpha 13 (February 13, 2012)
• Sieve upper bound increased up to 2³¹.
• Added new class invariants.
• New data files.
• Modified the backtrack strategy.

v4.0.0 - alpha 12 (November 8, 2011)
• New data files.

v4.0.0 - alpha 11 (October 10, 2011)
• Fixed two bugs regarding the backtracking stuff.
• New data files.
• Added [Setup, resume:n] sections to .cr files.

v4.0.0 - alpha 10 (August 22, 2011)
• Fixed a bug regarding the verification stuff. Thanks to Tom Wu who reported it.
• Minor cosmetic changes.

v4.0.0 - alpha 9 (August 14, 2011)
• Very first 64-bit version.
• No more Confirm to abort button (clicking on the Abort button immediately terminates the certifications/verifications).
• The .t<n> and .s<n> binary files are not compatible with the 32-bit versions (it is impossible to resume a certification started with a 32-bit version).
• New help file.

v4.0.0 - alpha 8 (July 9, 2011)
• New data files.
• Modified the numbering of the backtracked tests (.cr files).

v4.0.0 - alpha 7 (June 8, 2011)
• Fixed a bug that was sleeping since 10 years: some very particular numbers could be rejected (with the message The candidate is presumably a square) whereas they might be prime. Thanks to David Harrison who reported it.
• Fixed a bug regarding the backtracking indicator. Thanks to Tom Wu who reported it.
• Number of possible concurrent tasks increased up to 16.
• Miscellaneous cosmetic and naming changes.

v4.0.0 - alpha 6 (May 25, 2011)
• Range of the Sieve upper bound increased from (2²¹..2²⁸) to (2²⁰..2³⁰).
• N±1 and EC tests fully parallelized.

v4.0.0 - alpha 5 (May 9, 2011)
• Fixed a bug regarding the primo.xd15 data file. Thanks to Tom Wu who reported it.

v4.0.0 - alpha 4 (May 9, 2011)
• Better parallelization of the so-called Phase 1.
• New data files.
• Added a Certification reports option.

v4.0.0 - alpha 3 (April 24, 2011)
• Fixed cosmetic bugs.
• Slightly better tuning (hopefully).

v4.0.0 - alpha 2 (April 14, 2011)
• First Linux release.

v3.0.9.1
• Fixed a bug concerning the signatures of very small prime (less than 2⁴⁸) certificates. Thanks to Kevin Trinder who reported it.

v3.0.6
• An incoherence reported by Norman Luhn has been fixed (when verifying a certificate, if there was an expression in the [Candidate] section, Primo did not check whether this expression was equal to the candidate value).

v2.3.1
• Fixed a bug that could lead to the internal error 2.15.2. Thanks to Wolfgang Ehrhardt who reported it.

v2.3.0
• Use of new class invariants. Thanks to Michael Scott who kindly computed the needed modular functions.

v2.1.2
• Installation problem fixed. Thanks to Sergey Lopatin who reported it.