Messages in this thread | | | Date | Fri, 10 Mar 2006 12:05:06 +0100 | From | Bart Hartgers <> | Subject | Re: How can I link the kernel with libgcc ? |
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Denis Vlasenko wrote: > On Friday 10 March 2006 05:47, Carlos Munoz wrote: >> Lee Revell wrote: > > What? You are using log10 only twice! > > if (!(siu_obj_status & ST_OPEN)) { > ... > /* = log2(over) */ > ydef[22] = (u_int32_t)(log10((double)(over & 0x0000003f)) / > log10(2)); > ... > } > else { > ... > if (coef) { > ydef[16] = 0x03045000 | (over << 26) | (tap - 4); > ydef[17] = (tap * 2 + 1); > /* = log2(over) */ > ydef[22] = (u_int32_t) > (log10((double)(over & 0x0000003f)) / log10(2)); > } > > Don't you think that log10((double)(over & 0x0000003f)) / log10(2) > can have only 64 different values depending on the result of (over & 0x3f)? > > Obtain them from precomputed uint32_t log10table[64].
And since you're actually trying to do log2 [log10(x)/log10(2) = log2(x)] and casting the result to an integer, aren't you really looking for the position of the highest 1 bit or something like that? That doesn't need FP at all.
Groeten, Bart
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-- Bart Hartgers - TUE Eindhoven - http://plasimo.phys.tue.nl/bart/contact/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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