I thought I might as well see just how slowly mlucas runs on a last-year's ARM.

The current downloadable tarfile of mlucas (Mlucas_10.09.2011; I appreciate this is old, is there a newer place to look?) doesn't build unless USE_SSE2 is defined, because the section around lines 1441 to 1458 of radix16_ditN_cy_dif1.c (only) uses *bjmodn0 which is incorrect if !USE_SSE2

I did

#if !defined(USE_SSE2)

#define BJSTAR

#else

#define BJSTAR *

#endif

then replaced *bjmodn0 with BJSTAR modn0

but I appreciate that makes the code a bit ugly.

It's really not terribly fast:

Code:

M2614999: using FFT length 128K = 131072 8-byte floats.
this gives an average 19.950859069824219 bits per digit
Using complex FFT radices 8 16 32 16
1000 iterations of M2614999 with FFT length 131072 = 128 K
Res64: 1A184504D2DE2D3C. AvgMaxErr = 0.000000000. MaxErr = 0.000000000. Program: E3.0x
Res mod 2^36 = 20717645116
Res mod 2^35 - 1 = 5934292942
Res mod 2^36 - 1 = 4090378120
Clocks = 00:00:45.939
M42643801: using FFT length 2304K = 2359296 8-byte floats.
this gives an average 18.074799007839626 bits per digit
Using complex FFT radices 9 8 8 8 16 16
10 iterations of M42643801 with FFT length 2359296 = 2304 K
Res64: 9BDB491DF4C00002. AvgMaxErr N/A. MaxErr = 0.000000000. Program: E3.0x
Res mod 2^36 = 59940798466
Res mod 2^35 - 1 = 11033316518
Res mod 2^36 - 1 = 15286304084
Clocks = 00:00:10.410

(for comparison, a 3.4GHz Sandy Bridge machine gave 0.045s/i for 42643801 and 0.0021s/i for 2614999; so about 22 times faster)

I'm trying different compiler options; I tried enabling multi-threading but got a message saying that the sensitivity list for radix44 needed updating. Have you got a newer version of that?