mfaktc: a CUDA program for Mersenne prefactoring

[Prime95]

I installed 64-bit Ubuntu 10.04, Cuda version 5, and mfaktc-0.18.tar.gz. I did a make. Running the built mfaktc fails all the self-tests. Where do I go from here?

BTW, I built CUDALucas 2.0.1 and it works just fine on my GTX 460.

[Dubslow]

Isn't CUDA 5 still in preview? Perhaps there's something CUDA 5 doesn't like about mfaktc. (I assume CUDALucas was built with CUDA 5? I know that it automatically targets arch_1.3, which would force CUDA < 5, so that may be why it avoided issues.)

[Prime95]

A more general question from a Linux and CUDA neophyte.

What is the recommended development environment for GPU programming? Is there a Linux IDE that is integrated with CUDA debugging and profiling tools?

[chalsall]

Originally Posted by Prime95

Is there a Linux IDE that is integrated with CUDA debugging and profiling tools?

http://ydl.net/eclipse_cuda_plugin/

For those who use IDEs, Eclipse is your (Open Source) friend....

[TheJudger]

Originally Posted by Prime95

I installed 64-bit Ubuntu 10.04, Cuda version 5, and mfaktc-0.18.tar.gz. I did a make. Running the built mfaktc fails all the self-tests. Where do I go from here?

BTW, I built CUDALucas 2.0.1 and it works just fine on my GTX 460.

So it builds without much warnings (usually there are some warning in sieve.c about signed/unsigned variable mismatch)?
I guess you're using CUDA 5.0.7 (preview release), right?
Fails all the selftest -> missing factors (no factor found) or wrong factors?
I guess you're using default src/params.c and mfaktc.ini, right?

You can try to enable some debugging code in src/params.h:

• If you enable RAW_GPU_BENCH the effect is basically that you disable the sieve code (ofcouse this slows down the application)
• you can try to enable CHECKS_MODBASECASE and USE_DEVICE_PRINTF, this will enable debug code in the long integer division code, if something is really screwed the USE_DEVICE_PRINTF will cause overflows because of too much printfs in GPU context.

Another option to test: add -malign-double to the CFLAGS in the Makefile (default in mfaktc-0.19...). There are some known issues with CUDA/gcc about alignment of 64bit variables.

Can you provide me some lines of ./mfaktc.exe -v 2 -st? (just start it and stop after a few seconds by pressing <Ctrl>+C) and send me the screen output.

I'll try CUDA 5.0.7 later on my system.

Oliver

P.S. at least it is good to know that the selftest works...

[Prime95]

Originally Posted by TheJudger

So it builds without much warnings (usually there are some warning in sieve.c about signed/unsigned variable mismatch)?
I guess you're using CUDA 5.0.7 (preview release), right?
Fails all the selftest -> missing factors (no factor found) or wrong factors?
I guess you're using default src/params.c and mfaktc.ini, right?

Can you provide me some lines of ./mfaktc.exe -v 2 -st? (just start it and stop after a few seconds by pressing <Ctrl>+C) and send me the screen output.

Correct - a simple install and make without modifying anything. I'll try your debug suggestions later. Here is the output you wanted:

mfaktc v0.18 (64bit built)

Compiletime options
  THREADS_PER_BLOCK         256
  SIEVE_SIZE_LIMIT          32kiB
  SIEVE_SIZE                193154bits
  SIEVE_SPLIT               250
  MORE_CLASSES              enabled

Runtime options
  SievePrimes               25000
  SievePrimesAdjust         1
  NumStreams                3
  CPUStreams                3
  GridSize                  3
  WorkFile                  worktodo.txt
  Checkpoints               enabled
  CheckpointDelay           30s
  Stages                    enabled
  StopAfterFactor           bitlevel
  PrintMode                 full
  AllowSleep                no

CUDA version info
  binary compiled for CUDA  5.0
  CUDA runtime version      5.0
  CUDA driver version       5.0

CUDA device info
  name                      GeForce GTX 460
  compute capability        2.1
  maximum threads per block 1024
  number of multiprocessors 7 (336 shader cores)
  clock rate                1502MHz

Automatic parameters
  threads per grid          917504

########## testcase 1/1557 ##########
Starting trial factoring M50804297 from 2^67 to 2^68
 k_min = 1599999998520
 k_max = 1900000000000
Using GPU kernel "71bit_mul24"
    class | candidates |    time |    ETA | avg. rate | SievePrimes | CPU wait
3387/4620 |     14.68M |  0.213s |   n.a. |  68.92M/s |       25000 |   13.45%
no factor for M50804297 from 2^67 to 2^68 [mfaktc 0.18 71bit_mul24]
ERROR: selftest failed for M50804297
  no factor found
tf(): total time spent:  0.219s

Starting trial factoring M50804297 from 2^67 to 2^68
 k_min = 1599999998520
 k_max = 1900000000000
Using GPU kernel "75bit_mul32"
    class | candidates |    time |    ETA | avg. rate | SievePrimes | CPU wait
3387/4620 |     14.68M |  0.145s |   n.a. | 101.24M/s |       28125 |    0.38%
no factor for M50804297 from 2^67 to 2^68 [mfaktc 0.18 75bit_mul32]
ERROR: selftest failed for M50804297
  no factor found
tf(): total time spent:  0.151s

Starting trial factoring M50804297 from 2^67 to 2^68
 k_min = 1599999998520
 k_max = 1900000000000
Using GPU kernel "95bit_mul32"
    class | candidates |    time |    ETA | avg. rate | SievePrimes | CPU wait
3387/4620 |     14.68M |  0.164s |   n.a. |  89.51M/s |       24609 |    0.34%
no factor for M50804297 from 2^67 to 2^68 [mfaktc 0.18 95bit_mul32]
ERROR: selftest failed for M50804297
  no factor found
tf(): total time spent:  0.170s

Starting trial factoring M50804297 from 2^67 to 2^68
 k_min = 1599999998520
 k_max = 1900000000000
Using GPU kernel "barrett79_mul32"
    class | candidates |    time |    ETA | avg. rate | SievePrimes | CPU wait
3387/4620 |     14.68M |  0.123s |   n.a. | 119.35M/s |       21532 |    0.49%
no factor for M50804297 from 2^67 to 2^68 [mfaktc 0.18 barrett79_mul32]
ERROR: selftest failed for M50804297
  no factor found
tf(): total time spent:  0.128s

[Prime95]

Originally Posted by TheJudger

[*]If you enable RAW_GPU_BENCH the effect is basically that you disable the sieve code (ofcouse this slows down the application)[*]you can try to enable CHECKS_MODBASECASE and USE_DEVICE_PRINTF, this will enable debug code in the long integer division code
Another option to test: add -malign-double to the CFLAGS in the Makefile (default in mfaktc-0.19...).

None of these helped or diagnosed any problems.

[TheJudger]

OK, next step: I'll try CUDA 5.0.7 on my system. I'm not sure if this will happen today.

Oliver

[Prime95]

Originally Posted by TheJudger

OK, next step: I'll try CUDA 5.0.7 on my system. I'm not sure if this will happen today.

Thanks. No rush, I'm primarily playing with gpusieve.

BTW, my bigger problem is NVidia's developer web site is down thanks to hackers.

[TheJudger]

I'm able to reproduce this issue with mfaktc 0.18 + CUDA toolkit 5.0.7-preview on openSUSE 12.1.

CUDA 5.0 driver + CUDA toolkit 4.2 -> OK
CUDA 5.0 driver + CUDA toolkit 5.0.7 -> fail

Oliver

[TheJudger]

first impressions:

• floatingpoint approximation for divisions seems to be OK
• data transfer seems to be OK

I see issue with carrys (using carry flag) in e.g. tf_barrett96.cu: mod_simple_96(). WTF?

So for now I can only say to everyone: Don't use CUDA Toolkit 5.0.7 for mfaktc!

Oliver