Editer un script bash pendant qu'il est en cours d'execution

On est en 2016 et bash n'est toujours pas capable de gérer correctement la situation où on édite un script alors qu'il est en cours d'exécution (gérer correctement, càd ignorer les changements et continuer à executer le script initial, et pas tenter d'executer un bout semi-aléatoire de la nouvelle version du script pour finalement se planter comme une merde)

Performance of the Raspberry pi 3

I just got a raspberry pi 3. I used to assume that its cpu (Cortex A53) should be quite bad, even when related to a good old cortex A9 (for example this document says that the performance is expected to be equivalent for both, while this one says the A53 is slightly slower than the A9). As I now have a cortex A9 (rk3188t) on a cheap device running picuntu, and a cortex A53 on the raspberry Pi, I can compare them. The default speed of the rk3188t is 1.4GHz but I have lowered it to the frequency of the raspberry pi for an easier comparison (using cpufreq-set). So both cpus are running at 1.2GHz. For the performance comparison, I have built and run the pffft benchmark on both:

time gcc-4.8 -O3 -DHAVE_FFTW -march=armv7-a -mtune=cortex-a9 -mfloat-abi=hard -mfpu=neon -ffast-math test_pffft.c pffft.c -o test_pffft_arm fftpack.c -lm -lfftw3f

(the raspbian distribution of the rpi3 is 32-bit so what I'm comparing here , since the A53 is 64-bit capable, is a A9 with a A53 running in 32-bit)

On the rk3188t@1.2Ghz, the compilation took 34 sec , while it took 24.9 on the pi, which is here 36% faster.

The execution took 109 sec on the rk3188t vs 66 sec on the pi, so for floating point stuff the pi is 65% faster.

If I look at the floatting point performance for pffft itself (so it is a measure of the neon simd floating point, not of the scalar floating point performance), the rk3188 reports a max value of 1164 MFlops for FFTs of length 1024 , while on the raspberry pi it achieves 2162 MFlops . So for neon stuff, the pi is 85% faster !

Here are the pffft results for the pi 3 on raspbian (when built with gcc-4.9 , which itself improves the pffft performance of 20% on both the rk3188 and the pi3 with respect to gcc-4.8, and with -mtune=cortex-a53 instead of cortex-a9, which brings another 7% of improvement):

| input len |real FFTPack|  real FFTW | real PFFFT | |cplx FFTPack|  cplx FFTW | cplx PFFFT |
|       64  |      521   |      672   |     1303   | |      534   |      887   |     1470   |
|       96  |      429   |      340   |     1253   | |      422   |      864   |     1323   |
|      128  |      508   |      740   |     1571   | |      491   |      742   |     1502   |
|      160  |      525   |      750   |     1626   | |      483   |      931   |     1463   |
|      192  |      544   |      852   |     1641   | |      495   |      877   |     1548   |
|      256  |      639   |      684   |     2007   | |      570   |      778   |     1727   |
|      384  |      483   |      873   |     1724   | |      436   |      795   |     1531   |
|      480  |      495   |      761   |     1749   | |      433   |     1040   |     1492   |
|      512  |      548   |      765   |     2043   | |      489   |      873   |     1670   |
|      640  |      557   |      892   |     2004   | |      481   |      863   |     1579   |
|      768  |      571   |      818   |     1980   | |      486   |      892   |     1684   |
|      800  |      549   |      637   |     1928   | |      450   |      657   |     1564   |
|     1024  |      645   |      842   |     2328   | |      540   |      914   |     1764   |
|     2048  |      586   |      869   |     2151   | |      487   |      931   |     1583   |
|     2400  |      530   |      672   |     1803   | |      422   |      681   |     1379   |
|     4096  |      631   |      867   |     2079   | |      476   |      843   |     1439   |
|     8192  |      515   |      811   |     1611   | |      418   |      730   |     1345   |
|     9216  |      503   |      789   |     1568   | |      424   |      812   |     1347   |
|    16384  |      501   |      749   |     1552   | |      418   |      699   |     1239   |
|    32768  |      479   |      680   |     1396   | |      346   |      529   |      825   |
|   262144  |      244   |      327   |      398   | |      240   |      409   |      387   |
|  1048576  |      229   |      270   |      350   | |      211   |      301   |      355   |

update: maybe I should say a word about the audio quality of the built-in headphone output of the rpi3 ? it is utter crap. Not sure if mine has a hardware issue or if the driver is doing some crazy shit but the output is mixed with some horrible electronic noise coming