Are hardware specs relevant in software performance comparisons? I notice occasionally in blogs or articles comparing different languages, algorithms, etc. that the author will divulge info about the processor used in the testing. Is this meaningful? 

Shouldn't the relative performance differences be hardware-agnostic? That is, if Language A executes in twice the time as Language B, shouldn't that roughly persist no matter the hardware?
Yes, hardware specs are relevant.  No, relative performance differences are not hardware-agnostic.

Suppose I find that editing a certain movie on my laptop takes twice as long as printing a certain Word document on my laptop.  Does this mean if I do those two tasks on my desktop computer, the movie editing task will also take twice as long as printing the Word document?  No, not necessarily.

Maybe my desktop computer has a great GPU (graphics card) but my laptop doesn't have a GPU.  The GPU can be expected to speed up the movie-editing task, but it won't speed up printing from Word.  So, on my desktop it's even possible that the movie-editing task might be faster than the printing task.

This is one reason why hardware specs are relevant.