What's New: New Features in Version 20.x of Prime95

# NEW FEATURES IN VERSION 20.x of PRIME95.EXE

## New Features in Version 20.6 of Prime95

1. A crash bug was fixed. If you did P-1 factoring followed by trial factoring, then if you found a factor unallocated memory was accessed usually resulting in a crash.

## New Features in Version 20.5 of Prime95

1. A rare error was fixed. When the memory settings changed during the GCD step in P-1 or ECM factoring, then a spurious "ERROR: Factor does not divide N!" error was raised.

## New features in Version 20.4 of Prime95

1. If stage 2 of P-1 was postponed because of insufficient memory, the program did not restart stage 2 when nighttime started. This bug was fixed.
2. By default, PII-300's and faster get first-time LL tests, P-90 and faster get double-checking work, and all slower machines get factoring work.
3. An ECM bug during stage 2 init on huge exponents caused false ILLEGAL SUMOUT errors. This bug was fixed.

## New features in Version 20.3 of Prime95

1. Another fairly uncommon ECM bug was fixed. The bug caused "Factor does not divide N!" errors.
2. A couple of minor bugs in computing the optimal P-1 bounds to use prior to a Lucas-Lehmer test were fixed. The program now does a better job at estimating the memory required in P-1 stage 2. Finally, although P-1 stage 2 working set size is unchanged, the program allocates less memory in stage 2.
3. Prime95 no longer searches for a smaller factor when trial factoring discovers a factor. The reasons are two-fold.

1. Version 19 had a bug where stopping and restarting the program bypassed the search for smaller factors. Thus, my database may already be missing smaller factors.
2. As we factor larger exponents to a deeper depth it may no longer be a quick job to determine if there are smaller factors. Note, that version 20 will still look for smaller factors if you are looking for factors below 2^60 with the FactorOverride option in undoc.txt.

4. The undocumented AMPM feature controls how times are formatted in the Options/CPU dialog box.

## New features in Version 20.2 of Prime95

1. If P-1 stage 1 completed and there was not enough memory to start stage 2 immediately, then an incorrect save file was generated. This bug was introduced in version 20.1. Upon restart of the P-1 factoring job a crash or other unpredictable behavior was possible. This bug was fixed and this version has special code to properly read these incorrect save files.
2. P-1 will restart any time the memory settings change. This is done so that the optimal P-1 bounds can be computed with the new memory settings.
3. A bug in ECM testing was fixed.

## New features in Version 20.1 of Prime95

1. A bug in the new GCD code was fixed.
2. Timings in the P-1 stage are no longer cumulative. There is a new feature in undoc.txt for those that prefer cumulative timings.
3. Messages are now output prior to beginning the lengthy GCD.
4. The FactorOverride undocumented feature (not for use with PrimeNet) now supports factoring to a deeper level than prime95 would ordinarily factor.
5. A bug where the worktodo.ini entry was not removed if P-1 found a factor was fixed.
6. If P-1 finds a factor it now deletes any Lucas-Lehmer intermediate files.
7. A crash bug when continuing from a P-1 stage 2 save files with different available memory parameters was fixed.
8. Resuming an LL test now outputs a line to the screen.
9. The Test/Status display now correctly calculates the estimated completion time for an LL test when P-1 factoring is in progress.
10. Advanced/Factor menu choice was deleted.
11. A bug in computing P-1 stage 2 percentage complete was fixed.

## New features in Version 20.0 of Prime95

1. The program now does some P-1 factoring prior to running first time and double-checking Lucas-Lehmer tests. This will increase overall GIMPS throughput. If you install version 20 in the middle of an LL test the program will run the P-1 step if the LL test is less than 50% complete.
2. The Options/CPU dialog box now asks how much memory the program can use during the P-1 factoring. See the "Setting Available Memory" section in the readme.txt file.
3. Stage 1 of P-1 factoring is now faster.
4. The GCD used in P-1 and ECM factoring is now faster.
5. The Test/Manual Operation menu choice has been deleted.
6. The memory options in P-1 and ECM dialog boxes have been deleted.
7. The "send new completion dates" checkbox was moved from the Test/PrimeNet dialog box to the Advanced/Manual Communication dialog box.
8. A bug in estimating time remaining for a factoring job was fixed.
9. AdvancedFactor now writes a line to the worktodo.ini - just like all the other work types.
10. ECM and P-1 are now consistent with Lucas-Lehmer testing in the use of the "Iterations between screen outputs" setting. An iteration is defined as the time it takes to do a squaring. If you are doing ECM on small exponents you will probably want to increase this setting.