Alexander Leidinger

Just another weblog

Mar
16

Ideas page updated

I updated my ideas page. I added an entry about using com­pressed air to auto­mat­i­cally remove snow (or sim­i­lar) from solar cells, and an entry about maybe using heat from ther­mal solar cells to gen­er­ate elec­tric­ity at home. I also updated the entry for non-optimal weather opti­mized solar cells with a link to a com­pany which seems to do some­thing sim­i­lar (using a lens) to reduce the cost of solar pan­els. To cool down the pho­to­voltaic cells, the com­pany is using a heat exchanger to make a com­bined photovoltaic/thermal panel. Unfor­tu­nately they are mak­ing an unfair com­par­i­son of the com­bined out­put of this panel (the ther­mal power out­put is much higher than the elec­tric power out­put) with a nor­mal pho­to­voltaic cell. A nor­mal house­hold needs more elec­tric­ity than heat so you do not want to use a lot of such pan­els, but depend­ing on the fea­si­bil­ity of my idea about using heat to pro­duce elec­tric­ity, such a panel could be interesting.

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Mar
12

Google’s new RE engine

I stum­bled over Google’s new RE engine. Unfor­tu­nately it is not han­dling back­ref­er­ences, so it is not a drop-in replace­ment for the reg­u­lar expres­sions code in FreeBSD. It has a POSIX mode, but this only seems to be enough for the egrep syn­tax. For peo­ple which need back­ref­er­ences, they refer to the Google Chrome’s RE engine irreg­exp which in turn ref­er­ences a paper from 2007 which is titled Reg­u­lar Expres­sion Match­ing Can Be Sim­ple And Fast.

The tech­niques in the paper can not be applied to the irreg­exp engine, but maybe could help to speed up awk, egrep and sim­i­lar programs.

I think it would be inter­est­ing to com­pare those recent devel­op­ments to what we have in FreeBSD, and if they are faster, to see if it is pos­si­ble to improve the FreeBSD imple­men­ta­tion based upon them (either by writ­ing new code, or by import­ing exist­ing code, depend­ing on the cor­re­spond­ing license and the lan­guage the code is writ­ten in).

Maybe a can­di­date for the GSoC?

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