-----Original Message----- From: Geoffrey Jacobs [mailto:gdjac...@gmail.com] Sent: Monday, March 18, 2013 10:02 PM To: Lux, Jim (337C) Cc: beowulf@beowulf.org Subject: Re: [Beowulf] Power calculations , double precision, ECC and power of APU's
On 03/18/2013 07:09 PM, Lux, Jim (337C) wrote: > > If you were processing all the RF signals available in the HF band you might > need DP. The instantaneous dynamic range can be around 130dB within a small > subband, and that's on the order of 21-22 bits, and if you look at the entire > 2-30 MHz spectrum, you probably have more range than can be accommodated in > the 24 bit mantissa of a SP floating point. > > Jim Lux I would be happy to be corrected, but isn't an SNR of 1000:1 considered to be excellent for a spectrograph (I'm thinking of particular datasets from Victor Blanco and CFHT). I don't believe any reduction pipeline or analysis for such data benefits from DP. I think there are high quality CCD sensors with 80dB+ dB dynamic range (max charge vs dark current of a few electrons/pixel) 10,000:1 voltage on the sense amplifier. Call it something like 14 bits.. So SP would be good enough for a lot of processing. (as would 32 bit fixed point.<grin>) _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
