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Performance loss on ARM CPU #1690
Reported by misterx on 22 Jun 2016 01:40 UTC
1.2rc4 brought improved performance. On x86 CPUs. On ARM such as the Raspberry Pi, the performance was worse than before.
In this forum post, it shows the loss:
Is the performance problem still present in the latest master branch? If so, please test using the commands below, with the binaries from the latest master branch:
Also, please post the output of:
Problem computing statistics on non-Intel/AMD systems
On line 3943, it defaults the number of parallel computations to one (1). The set of following lines will set it to four (4), only, if an i386 or amd64 machine.
Next, beginning at line 4092, the number of attempted computations performed are incremented by a constant value of four (4). This might then decremented by a constant of three (3), if
Finally, on line 4101, disaster strikes, as the smoking gun, always increments
Upon the speed test results being displayed (around line 3869), we see that computation is affected only by the global
This then leads to a displayed value that is wrong. If the displayed value is divided by four (4), one then has the actual number of keys tried per second.
In short, at least rc-3, and possibly older, computes all non-ia32 machines incorrectly. Previous speed test results must be divided by four (4) to obtain the real performance metric.