<div dir="ltr"><div><div><div>Specific application: one example would be a guard (a HOL function)<br>generated from a Guardol program. The input and output for the guard<br></div></div>are supplied by other code or hardware. My specification wouldn't <br>
mention I/O at all. All I would want is some kind of link between the execution <br>of the ISA code and the original function. <br><br></div>Konrad.<br><br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Jan 14, 2014 at 3:24 PM, Magnus Myreen <span dir="ltr"><<a href="mailto:magnus.myreen@cl.cam.ac.uk" target="_blank">magnus.myreen@cl.cam.ac.uk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im">On 15 January 2014 08:09, Konrad Slind <<a href="mailto:konrad.slind@gmail.com">konrad.slind@gmail.com</a>> wrote:<br>
> Thanks Magnus. I will do as you suggest.<br>
><br>
> I haven't absorbed your last point yet, so this is half-baked,<br>
> but I can imagine using the compiler to generate executables<br>
> that get linked in with I/O components coming from (say) a pre-existing<br>
> C library, so that the repl is not involved at all. Is that a possbile<br>
> scenario for cakeML?<br>
<br>
</div>Not currently, no. We aren't able to produce stand-alone executables.<br>
The invariants haven't been set up for the compiler to be used as a<br>
stand-alone thing. Hmmm... Do you have some specific application in<br>
mind? I'm guessing you'd like a foreign function interface.<br>
<br>
Regarding pre-existing C libraries: the current implementation of<br>
CakeML uses C's getc and putc for I/O, but these are code pointers<br>
that are passed into the verified blob of machine code and the proofs<br>
make assumptions about these code pointers (e.g. a call to putc puts<br>
the input char onto some output stream and then returns control<br>
according to the C calling convention). The C code that wraps the<br>
verified code (asm_code.s) is here, in case you want to see it:<br>
<br>
<a href="https://github.com/xrchz/vml/blob/master/x86-64/wrapper/wrapper.c" target="_blank">https://github.com/xrchz/vml/blob/master/x86-64/wrapper/wrapper.c</a><br>
<br>
Cheers,<br>
Magnus<br>
<div class="HOEnZb"><div class="h5"><br>
> Cheers,<br>
> Konrad.<br>
><br>
><br>
><br>
> On Tue, Jan 14, 2014 at 2:51 PM, Magnus Myreen <<a href="mailto:magnus.myreen@cl.cam.ac.uk">magnus.myreen@cl.cam.ac.uk</a>><br>
> wrote:<br>
>><br>
>> Hi Konrad,<br>
>><br>
>> > I've downloaded cakeML from git and have been building it. I was<br>
>> > warned<br>
>> > that I needed 16 GB to do everything, so I expected failure. But I<br>
>> > wanted<br>
>> > to see how far it got before crashing. Here's the error message:<br>
>><br>
>> As far as I know, the full bootstrap has only been successfully run on<br>
>> a 64 GB machine, but maybe Ramana had some data suggesting 16 GB would<br>
>> is enough.<br>
>><br>
>> > 294 declarations still to go<br>
>> > 0: (val opn_to_prim2)0 (val div_exc_cn)1 (val cdiv_exc)2 (val<br>
>> > eq_exc_cn)3<br>
>> > (val ceq_exc)4 (fun pat_to_cpat*)5 (fun exp_to_cexp*)6 (datatype<br>
>> > call_context)7 (fun lunion)8 (val lshift)9 (fun free_vars*)10 (val<br>
>> > bind_fv)11 (fun label_closures*)12 (val get_label)13 (val pushret)14<br>
>> > (fun<br>
>> > compile_envref)15 (val compile_varref)16 (val el_check)17 (val<br>
>> > bool_to_tag)18 (val unit_tag)19 runtime: 21m34s, gctime: 21m07s,<br>
>> > systime: 2m40s.<br>
>> > 1: (val block_tag)0 (fun num_fold)1 (val push_lab)2 (val emit_ceref)3<br>
>> > (val<br>
>> > emit_ceenv)4 (val closure_tag)5 (val cons_closure)6 (val update_refptr)7<br>
>> > (val compile_closures)8 (val prim1_to_bc)9 (val prim2_to_bc)10 (fun<br>
>> > compile*)Warning - Unable to increase stack - interrupting thread<br>
>> > runtime: 17m06s, gctime: 16m47s, systime: 3m42s.<br>
>> > Exception- Interrupt raised<br>
>> > Holmake: Failed script build for compileReplDecsScript - exited with<br>
>> > code 1<br>
>> > make: *** [all] Error 1<br>
>> ><br>
>> ><br>
>> > Questions:<br>
>> ><br>
>> > 1. Is this the expected place of failure? (This is on an 8 GB box<br>
>> > running<br>
>> > PolyML 5.5).<br>
>><br>
>> That looks like the expected choke point.<br>
>><br>
>> > 2. I just invoked "make" in the top level. What is the invocation if I<br>
>> > wanted to avoid<br>
>> > the memory-expensive bootstrap?<br>
>><br>
>> You'll need to replace<br>
>><br>
>> vml/bootstrap/compileReplDecsScript.sml<br>
>><br>
>> with<br>
>><br>
>> vml/bootstrap/compileReplDecsCheatScript.sml<br>
>><br>
>> and also delete "Cheat" in the second line in the file, i.e. the<br>
>> new_theory command.<br>
>><br>
>> > 2a. The build needs lem. This should be mentioned.<br>
>><br>
>> Yes, lem is required for silly Holmake reasons.<br>
>><br>
>> > 2b. In lem, the hol-lib directory has a spurious file called<br>
>> > stringScript.sml that<br>
>> > derails the build. I've talked to Scott about this already.<br>
>> ><br>
>> > 3. I would like to explore the verification aspects of the system. In<br>
>> > particular, suppose<br>
>> > I want to define (executable) functions in HOL and prove properties,<br>
>> > then somehow<br>
>> > map the functions to cakeML and get some sort of<br>
>> > "correctness-of-compilation"<br>
>> > theorem out that I can use to make a formal connection between the<br>
>> > properties, the<br>
>> > function, and the executable code.<br>
>> ><br>
>> > For example, I define factorial and prove that it is always<br>
>> > positive:<br>
>> ><br>
>> > val fact_def = Define `fact n = if n <= 0 then 1 else n * fact<br>
>> > (n-1)`;<br>
>> > (* The fact function could be over integers, if need be. *)<br>
>> ><br>
>> > val fact_pos = prove(``!n. 0 < fact n``, ....);<br>
>> ><br>
>> > ... and now what steps do I take? I have read the relevant papers<br>
>> > by<br>
>> > Magnus and<br>
>> > others, but now I am seeking more concrete hints.<br>
>><br>
>> To turn your fact function into CakeML, you'll need to run it through<br>
>> the translator, i.e. write a file like<br>
>><br>
>> vml/translator/ml_translator_demoScript.sml<br>
>><br>
>> for your fact function, which can use num. The translator turns HOL<br>
>> ``:num`` into CakeML ints and maintains an invariant that the CakeML<br>
>> ints are not negative.<br>
>><br>
>> To reason about the machine code or bytecode that executes this CakeML<br>
>> is a bit more tricky. The top-level theorem makes a statement about<br>
>> the whole system in terms of an input stream of characters and an<br>
>> output stream of characters. I guess we'd need a verified pretty<br>
>> printer to turn CakeML AST into a string that is guaranteed to parse<br>
>> back as that CakeML AST. Alternatively, one can try to evaluate (in<br>
>> the logic) a the application of the parser to a string representing<br>
>> that AST and check that the parser maps that string into the desired<br>
>> AST. Then you'll need to somehow talk about your fact function in the<br>
>> context of all the other code that gets input during execution of the<br>
>> read-eval-print loop. The final theorem would be about the output<br>
>> string and terminate/diverge behaviour of the entire system with the<br>
>> fact function fed in on the input stream.<br>
>><br>
>> I'm rather vague about the last parts because we haven't yet worked<br>
>> through all the details. But we aim to do so in conjunction with the<br>
>> verified HOL light case study.<br>
>><br>
>> Cheers,<br>
>> Magnus<br>
>><br>
>> > Thanks,<br>
>> > Konrad.<br>
>> ><br>
>> ><br>
>> > _______________________________________________<br>
>> > Users mailing list<br>
>> > <a href="mailto:Users@cakeml.org">Users@cakeml.org</a><br>
>> > <a href="https://lists.cakeml.org/listinfo/users" target="_blank">https://lists.cakeml.org/listinfo/users</a><br>
>> ><br>
><br>
><br>
</div></div></blockquote></div><br></div>