Re: [9fans] usb jtag
On Sun, Oct 2, 2011 at 8:52 PM, erik quanstrom wrote: > should the ctl file contain text? i get something that looks like it should > be a directory, but it's not. the manual page doesn't say what should be > in the jtag file. > Jtagxx is a directory. jtag is a connection to the jtag. ctl is ignored for now. It looks like reading from the ctl returns count rather than 0 which is why you are seeing noise. I'll send a patch. G.
Re: [9fans] circular fonctions: precision?
On Sun, Oct 02, 2011 at 12:06:18PM -0700, Bakul Shah wrote: > > > I sometimes wonder if the more common 64bits will not someday see > > CAD or related software go back to scaled integer arithmetic =E0 la > > Intergraph dgn, where 64bits is enough for the range of coordinates > > and precision used... > > double precision seems enough for most things. ieee754-2008 > has quad precision... Symbolic math package Macsyma (& Maxima) > has had bigfloats (arbitray precision floating point) for > decades. Supposedly some Common Lisp implementation have > those as well. Mechanical CAD packages would probably get > more benefit from symbolic math capabilities than just scaled > integers (keep everything in formulas until when you > absolutely need numerical results!). To resort to algebra (infinite precision by symbol combinations) is, indeed, a general rule. For symbolic math capabilities, I have wandered around the concept for geometrical description (like METAFONT/MetaPost, where there is this distinction that is mostly blurred in programming languages---except for basic conditionnals--- : the distinction between an assignation and an equation). But to come back to programming, when calculus is the crux, the more common/known even new! programming languages are not great tools, and "portability" i.e. proved accuracy of the implementation for a wide range of hardware/software is fuzzy. And it's amazing to see how one can rapidly face errors even with very basic computations. And even with integer arithmetic, not much help is guaranteed by languages. -- Thierry Laronde http://www.kergis.com/ Key fingerprint = 0FF7 E906 FBAF FE95 FD89 250D 52B1 AE95 6006 F40C
Re: [9fans] circular fonctions: precision?
On Sun, Oct 2, 2011 at 12:38 PM, wrote: > Is there some documentation about the precision of the circular (i.e > trigonometric) fonctions, depending on the (plan9) implementation and > the hardware? They are not terribly accurate. If you need accurate versions, the best I know are the ones that were written at Sun and included in the FreeBSD math library. There are copies on any FreeBSD machine and also in the vx32 distribution: http://code.swtch.com/vx32/src/tip/src/libvxc/msun. For Go, we started with implementations of the Plan 9 library algorithms but have been slowly replacing them with implementations of the Sun/FreeBSD algorithms for the improved accuracy. Russ
Re: [9fans] circular fonctions: precision?
On Oct 3, 2011, at 4:41 AM, tlaro...@polynum.com wrote: >> > But to come back to programming, when calculus is the crux, the more > common/known even new! programming languages are not great tools, and > "portability" i.e. proved accuracy of the implementation for a wide > range of hardware/software is fuzzy. And it's amazing to see how one can > rapidly face errors even with very basic computations. And even with > integer arithmetic, not much help is guaranteed by languages. Integer & rational arithmetic is guaranteed in Scheme and some other languages. In an R5RS compliant Scheme implementation you have for example (/ 5 7) => 5/7. (If only people get over their irrational fear of prefix syntax they would discover a great little language in Scheme.) But most prog. languages do not specify minimal required accuracy on standard floating pt. functions. May be because most language hackers are not numerical analysts!
Re: [9fans] circular fonctions: precision?
On Oct 3, 2011, at 6:03 AM, Russ Cox wrote: > For Go, we started with implementations of the Plan 9 library > algorithms but have been slowly replacing them with implementations > of the Sun/FreeBSD algorithms for the improved accuracy. Why not just use sun/FreeBSD functions in C? Unless of course go authors are planning to specify guaranteed minimum accuracy!
Re: [9fans] circular fonctions: precision?
> On Oct 3, 2011, at 4:41 AM, tlaro...@polynum.com wrote: >> > > But to come back to programming, when calculus is the crux, the more > > common/known even new! programming languages are not great tools, > > and "portability" i.e. proved accuracy of the implementation for a > > wide range of hardware/software is fuzzy. And it's amazing to see > > how one can rapidly face errors even with very basic computations. > > And even with integer arithmetic, not much help is guaranteed by > > languages. > > > Integer & rational arithmetic is guaranteed in Scheme and some other > languages. In an R5RS compliant Scheme implementation you have for > example (/ 5 7) => 5/7. (If only people get over their irrational > fear of prefix syntax they would discover a great little language in > Scheme.) But most prog. languages do not specify minimal required > accuracy on standard floating pt. functions. May be because most > language hackers are not numerical analysts! i think you've got it there. how do i stuff 5/7 in a 32-bit ethernet register? if you're close to the h/w, it's probablly just confusing to fight it. - erik
Re: [9fans] circular fonctions: precision?
On Mon, Oct 3, 2011 at 10:44 AM, Bakul Shah wrote: > Why not just use sun/FreeBSD functions in C? Because we are writing in Go. Russ
Re: [9fans] circular fonctions: precision?
On Oct 3, 2011, at 7:46 AM, erik quanstrom wrote: >> On Oct 3, 2011, at 4:41 AM, tlaro...@polynum.com wrote: >> >>> But to come back to programming, when calculus is the crux, the more >>> common/known even new! programming languages are not great tools, >>> and "portability" i.e. proved accuracy of the implementation for a >>> wide range of hardware/software is fuzzy. And it's amazing to see >>> how one can rapidly face errors even with very basic computations. >>> And even with integer arithmetic, not much help is guaranteed by >>> languages. >>> >> Integer & rational arithmetic is guaranteed in Scheme and some other >> languages. In an R5RS compliant Scheme implementation you have for >> example (/ 5 7) => 5/7. (If only people get over their irrational >> fear of prefix syntax they would discover a great little language in >> Scheme.) But most prog. languages do not specify minimal required >> accuracy on standard floating pt. functions. May be because most >> language hackers are not numerical analysts! > > i think you've got it there. how do i stuff 5/7 in a 32-bit ethernet > register? > if you're close to the h/w, it's probablly just confusing to fight it. Ethernet ctlrs have FP registers these days? Wow! It is just a different fight. Scheme has conversion functions + macros to do what you want. Also note that most people do not work as closely to h/w as perhaps you or I do. And of course, you don't have to use just one language. Funny you mention h/w. I have used scheme in the past for h/w testing as well as for generating code for a custom network processor. This NP had a 512 bit barrel shifter (could hold an entire 64 byte pkt and we could poke at any bitfield upto 32 bits in length). In my test library a 'shift' was (+ (quotient 512-bit-reg 2^32) new-32-bit-value)). Could've done in C but this was more fun and far fewer lines of code and far quicker to develop! I could represent an entire test pkt as a single number and shift into the barrelshifter etc. No need to worry about grotty indexing or off by 1 errors!
Re: [9fans] circular fonctions: precision?
On Oct 3, 2011, at 7:57 AM, Russ Cox wrote: > On Mon, Oct 3, 2011 at 10:44 AM, Bakul Shah wrote: >> Why not just use sun/FreeBSD functions in C? > > Because we are writing in Go. I don't get it. Surely go has a FFI? Or Are you planning to reimplement many libraries in go?
Re: [9fans] circular fonctions: precision?
On Mon, Oct 3, 2011 at 11:34 AM, Bakul Shah wrote: > I don't get it. Surely go has a FFI? Or Are you planning to reimplement many > libraries in go? Using FFI for square root is overkill. Russ
Re: [9fans] circular fonctions: precision?
On Mon, 03 Oct 2011 08:29:40 PDT Bakul Shah wrote: > In my test library a 'shift' was > (+ (quotient 512-bit-reg 2^32) new-32-bit-value)). Oops. I meant: (+ (* (quotient 512-bit-reg 2^32) 2^32)) new-32-bit-value) In one clock the top 32 bits shift out and new 32 bits shift in. It has been a while.
Re: [9fans] circular fonctions: precision?
On Mon, Oct 03, 2011 at 07:39:16AM -0700, Bakul Shah wrote: > > Integer & rational arithmetic is guaranteed in Scheme and some other > languages. In an R5RS compliant Scheme implementation you have for example (/ > 5 7) => 5/7. (If only people get over their irrational fear of prefix syntax > they would discover a great little language in Scheme.) But most prog. > languages do not specify minimal required accuracy on standard floating pt. > functions. May be because most language hackers are not numerical analysts! Thanks for your comments. I must really tackle Scheme some day! -- Thierry Laronde http://www.kergis.com/ Key fingerprint = 0FF7 E906 FBAF FE95 FD89 250D 52B1 AE95 6006 F40C
Re: [9fans] circular fonctions: precision?
On Mon, Oct 03, 2011 at 09:03:50AM -0400, Russ Cox wrote: > On Sun, Oct 2, 2011 at 12:38 PM, wrote: > > Is there some documentation about the precision of the circular (i.e > > trigonometric) fonctions, depending on the (plan9) implementation and > > the hardware? > > They are not terribly accurate. > > If you need accurate versions, the best I know are the ones > that were written at Sun and included in the FreeBSD math library. > There are copies on any FreeBSD machine and also in the > vx32 distribution: http://code.swtch.com/vx32/src/tip/src/libvxc/msun. > > For Go, we started with implementations of the Plan 9 library > algorithms but have been slowly replacing them with implementations > of the Sun/FreeBSD algorithms for the improved accuracy. Thanks for the tips. I will put the various clues given in the thread at least to have a better understanding about what my code relies upon. -- Thierry Laronde http://www.kergis.com/ Key fingerprint = 0FF7 E906 FBAF FE95 FD89 250D 52B1 AE95 6006 F40C
Re: [9fans] copying fossil filesystem to a bigger disk
On Mon Oct 3 19:08:49 EDT 2011, slash.9f...@gmail.com wrote: > > the way to interpret this information is you may use 512 > > byte sectors if you really want to suffer terrible performance > > (usually 1/3 the normal performance for reasonablly random > > workloads.) > > That doesn't sound tempting at all. I am still within Amazon's return > window. Can anyone recommend a 2 TB SATA drive that works on our > favorite operating system out of the box at full speed? If it's quiet > and cheap, all the better. > > > let me think a bit about the correct solutions to this. it's clear > > to me that we just can't assume 512-byte sectors any more. > > I knew Plan 9 is picky about hardware, but a hard disk? *sigh* relax, it's really just the mbr code and fdisk that don't like a non 512-byte sector size. in fact, as long as you don't boot from it, you can use the disk as-is. - erik
Re: [9fans] copying fossil filesystem to a bigger disk
> the way to interpret this information is you may use 512 > byte sectors if you really want to suffer terrible performance > (usually 1/3 the normal performance for reasonablly random > workloads.) That doesn't sound tempting at all. I am still within Amazon's return window. Can anyone recommend a 2 TB SATA drive that works on our favorite operating system out of the box at full speed? If it's quiet and cheap, all the better. > let me think a bit about the correct solutions to this. it's clear > to me that we just can't assume 512-byte sectors any more. I knew Plan 9 is picky about hardware, but a hard disk? *sigh*
Re: [9fans] copying fossil filesystem to a bigger disk
On Mon Oct 3 19:08:49 EDT 2011, slash.9f...@gmail.com wrote: > > the way to interpret this information is you may use 512 > > byte sectors if you really want to suffer terrible performance > > (usually 1/3 the normal performance for reasonablly random > > workloads.) > > That doesn't sound tempting at all. I am still within Amazon's return > window. Can anyone recommend a 2 TB SATA drive that works on our > favorite operating system out of the box at full speed? If it's quiet > and cheap, all the better. > > > let me think a bit about the correct solutions to this. it's clear > > to me that we just can't assume 512-byte sectors any more. > > I knew Plan 9 is picky about hardware, but a hard disk? *sigh* xp won't use it correctly either. in fact, if you're using a standard fdisk layout, chances are things are a little sideways on nearly any os. in any event, if i were buying a 2t hard drive today, i'd get http://www.newegg.com/Product/Product.aspx?Item=N82E16822136365 since i'm paranoid about hard drives and only get enterprise ones. if you're not, then (most) anything with 512-byte sectors should be no troubles. the easiest way to check is to do some math. multiply the number of sectors (that's always on the datasheet) by the 512, and see if that equals the claimed capacity. - erik
[9fans] cb bug
no suprise here, cb sometimes eats unicode. i'm currently too lazy to track the problem down. - erik
