siddharthrai/avxtest

Testing AVX capabilities with GCC

avxtest

This simple repository is for testing AVX capabilities with GCC. The source code is based on the one provided here: https://thinkingandcomputing.com/2014/02/28/using-avx-instructions-in-matrix-multiplication/ - which has been originally authored by Yifei Teng, namely the code in the file avxtest.cpp.

The code in this repository was further changed to give formatted results with more precision and at the end is shown the differences in the results.

The file avxtest64.cpp was adapted from avxtest.cpp to do double precision operations, instead of doing single precision operations.

Author of these changes: Bruno Santos, namely wyldckat@github.

Compiling

Simply run:

g++ -O3 -mavx avxtest.cpp -o avxtest
g++ -O3 -mavx avxtest64.cpp -o avxtest64

Or use the native settings, which can give you an additional optimization edge:

g++ -O3 -march=native avxtest.cpp -o avxtest
g++ -O3 -march=native avxtest64.cpp -o avxtest64

Or if no AVX is available, build the noavxtest alternatives:

g++ -O3 -march=native noavxtest.cpp -o noavxtest
g++ -O3 -march=native noavxtest64.cpp -o noavxtest64

Example output

These results were obtained with an AMD A10-7850K, while it was running other applications, therefore these are not optimum results. For detailed performance results: https://github.com/wyldckat/avxtest/wiki/A10-7850K-with-DDR3-at-2133-MHz

Notice that since it's a 64-bit processor, it takes roughly the same time to do the operations with standard x86/x86_64 FPU, versus the results achieved with AVX, where it takes roughly twice as long to the operations with AVX and double precision.

avxtest

Time taken (ms): 44478.285156
46.645702362, 54.693763733, 52.523517609, 46.882259369, 47.732662201, 53.505905151, 44.757362366, 53.78931427, 50.922969818, 47.973320007, 50.980171204, 51.735042572, 57.411094666, 50.251522064, 48.735942841, 50.678451538, 54.797599792, 52.394363403, 49.601345062, 48.174781799, 51.200325012, 43.908599854, 49.559474945, 48.012435913, 

Time taken (ms): 6253.0961914
46.645690918, 54.693771362, 52.523513794, 46.882263184, 47.732650757, 53.505893707, 44.757354736, 53.789325714, 50.922950745, 47.973320007, 50.980171204, 51.735046387, 57.41109848, 50.251529694, 48.735939026, 50.678451538, 54.797599792, 52.394359589, 49.601318359, 48.174793243, 51.200325012, 43.908607483, 49.55947876, 48.012435913, 

    Without AVX  |    With AVX      |   Difference
    46.645702362 |     46.645690918 | 1.1444091797e-05
    54.693763733 |     54.693771362 | -7.6293945312e-06
    52.523517609 |     52.523513794 | 3.8146972656e-06
    46.882259369 |     46.882263184 | -3.8146972656e-06
    47.732662201 |     47.732650757 | 1.1444091797e-05
    53.505905151 |     53.505893707 | 1.1444091797e-05
    44.757362366 |     44.757354736 | 7.6293945312e-06
    53.78931427  |     53.789325714 | -1.1444091797e-05
    50.922969818 |     50.922950745 | 1.9073486328e-05
    47.973320007 |     47.973320007 |                0
    50.980171204 |     50.980171204 |                0
    51.735042572 |     51.735046387 | -3.8146972656e-06
    57.411094666 |      57.41109848 | -3.8146972656e-06
    50.251522064 |     50.251529694 | -7.6293945312e-06
    48.735942841 |     48.735939026 | 3.8146972656e-06
    50.678451538 |     50.678451538 |                0
    54.797599792 |     54.797599792 |                0
    52.394363403 |     52.394359589 | 3.8146972656e-06
    49.601345062 |     49.601318359 | 2.6702880859e-05
    48.174781799 |     48.174793243 | -1.1444091797e-05
    51.200325012 |     51.200325012 |                0
    43.908599854 |     43.908607483 | -7.6293945312e-06
    49.559474945 |      49.55947876 | -3.8146972656e-06
    48.012435913 |     48.012435913 |                0

avxtest64

Time taken (ms): 44543.2169999999969
46.6456921874999821, 54.6937718749999746, 52.5235124999999954, 46.8822578125000149, 47.7326531249999988, 53.5058921874999882, 44.7573531250000158, 53.7893234374999736, 50.9229515625000033, 47.9733187499999971, 50.9801671874999798, 51.735049999999994, 57.4110968749999913, 50.2515296874999891, 48.7359359374999883, 50.6784578124999712, 54.7975999999999956, 52.3943593750000289, 49.6013171875000296, 48.174790625, 51.2003234374999892, 43.9086031250000275, 49.5594781250000054, 48.012434374999998, 

Time taken (ms): 13095.6270000000004
46.6456921874999821, 54.6937718749999746, 52.5235124999999954, 46.8822578125000149, 47.7326531249999988, 53.5058921874999882, 44.7573531250000158, 53.7893234374999736, 50.9229515625000033, 47.9733187499999971, 50.9801671874999798, 51.735049999999994, 57.4110968749999913, 50.2515296874999891, 48.7359359374999883, 50.6784578124999712, 54.7975999999999956, 52.3943593750000289, 49.6013171875000296, 48.174790625, 51.2003234374999892, 43.9086031250000275, 49.5594781250000054, 48.012434374999998, 

      Without AVX     |       With AVX         |      Difference
  46.6456921874999821 |    46.6456921875000035 | -2.13162820728030056e-14
  54.6937718749999746 |     54.693771875000003 | -2.84217094304040074e-14
  52.5235124999999954 |    52.5235125000000025 | -7.10542735760100186e-15
  46.8822578125000149 |    46.8822578124999865 | 2.84217094304040074e-14
  47.7326531249999988 |    47.7326531250000059 | -7.10542735760100186e-15
  53.5058921874999882 |    53.5058921875000024 | -1.42108547152020037e-14
  44.7573531250000158 |    44.7573531250000016 | 1.42108547152020037e-14
  53.7893234374999736 |     53.789323437500002 | -2.84217094304040074e-14
  50.9229515625000033 |    50.9229515624999962 | 7.10542735760100186e-15
  47.9733187499999971 |    47.9733187499999971 |                      0
  50.9801671874999798 |    50.9801671875000011 | -2.13162820728030056e-14
   51.735049999999994 |    51.7350500000000011 | -7.10542735760100186e-15
  57.4110968749999913 |    57.4110968749999984 | -7.10542735760100186e-15
  50.2515296874999891 |    50.2515296874999962 | -7.10542735760100186e-15
  48.7359359374999883 |    48.7359359375000025 | -1.42108547152020037e-14
  50.6784578124999712 |    50.6784578124999925 | -2.13162820728030056e-14
  54.7975999999999956 |     54.797600000000017 | -2.13162820728030056e-14
  52.3943593750000289 |    52.3943593749999863 | 4.26325641456060112e-14
  49.6013171875000296 |    49.6013171875000012 | 2.84217094304040074e-14
         48.174790625 |    48.1747906250000071 | -7.10542735760100186e-15
  51.2003234374999892 |    51.2003234375000105 | -2.13162820728030056e-14
  43.9086031250000275 |    43.9086031249999991 | 2.84217094304040074e-14
  49.5594781250000054 |    49.5594781250000125 | -7.10542735760100186e-15
   48.012434374999998 |     48.012434374999998 |                      0