Alec Mihailovs

Dr. Aleksandrs Mihailovs

4350 Reputation

20 Badges

15 years, 76 days
Mihailovs, Inc.
Owner, President, and CEO
Tyngsboro, Massachusetts, United States

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I received my Ph.D. from the University of Pennsylvania in 1998 and I have been teaching since then at SUNY Oneonta for 1 year, at Shepherd University for 5 years, at Tennessee Tech for 2 years, at Lane College for 1 year, and this year I taught at the University of Massachusetts Lowell. My research interests include Representation Theory and Combinatorics.

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These are Posts that have been published by Alec Mihailovs

After Poker's Black Friday (April 15), I started to think about moving to Canada, and I realized that I know very little about our northern neighbor.

I would appreciate any suggestions about a nice place with not very expensive rent (for a handicapped accessible house), safe for living, with a (very) good Internet connection, not very far from shopping places (do you have Walmarts?) etc.

Being close (in, say, 50 miles or less) to a casino with a poker room is desirable, but not absolutely necessary.

Thank you,
Alec

External calling functions from Windows dlls in Maple uses __stdcall calling convention.

Most Windows dlls including <windows.h> are using that convention (called also WINAPI). However, C runtime dll (msvcrt.dll) and most mathematical dlls - such as gsl, PARI, etc. which would be very useful, are using __cdecl calling convention and functions from them can not be easily called from Maple. One has to create a wrapper dll with __stdcall calling convention for that. In particular, Axel Vogt did that for a part of PARI.

Would that be possible for Maplesoft developers to add option CDECL in define_external in Maple 15 allowing calling C library functions and functions from gsl, PARI, etc. directly from Maple, without a burden of writing __stdcall wrappers for them first?

Just looked at the badges pages (clicking on the corresponding tab at the top).

88 people (including me) earned Tumbs-up badge, but only 50 people are listed there, and it says "page 1 of 1", there is no 2nd page - and unfortunately I didn't find myself there.

Even more interesting - clicking on most earned badges - such as 1st questions etc. - there are many pages, but only the first page for every badge have people listed - all the other pages are empty.

A couple of days ago I found out that gzread from the zlib library can be used for fast reading of binary files in Maple from the disk to memory - about 100 times faster than readbytes - something like in the following simplified example, 

A:=Array(1..2^26,99,datatype=integer[1]):

time(writebytes("A",A));close("A");

                                9.360

B:=Array(1..2^26,1,datatype=integer[1]):
time(readbytes("A",B));close("A");

                                8.065
B[1],B[-1];

                                99, 99

myreadbytes:=proc(f)
local gzopen, gzread, gzclose, n, p, A;
gzopen:=define_external('gzopen',
    'path'::string,
    'mode'::string,
    'RETURN'::integer[4],
    'LIB'="zlibwapi.dll");
gzread:=define_external('gzread',
    'file'::integer[4],
    'buf'::REF(ARRAY(datatype=integer[1])),    
    'len'::integer[4],
    'RETURN'::integer[4],
    'LIB'="zlibwapi.dll");
gzclose:=define_external('gzclose',
    'file'::integer[4],
    'RETURN'::integer[4],
    'LIB'="zlibwapi.dll");
n:=FileTools:-Size(f);
A:=Array(1..n,datatype=integer[1]);
try p:=gzopen(f,"rb");
if gzread(p,A,n)=n
then return A end if
finally gzclose(p)
end try
end proc:
time(assign(C=myreadbytes("A")));

                                0.062

C[1],C[-1];

                                99, 99

'time(myreadbytes("A"))'$5;


                  0.078, 0.062, 0.046, 0.046, 0.046

E:=Array(1..2^26,2,datatype=integer[1]):
time(ArrayTools:-Copy(A,E));

                                0.093

That needs some tweaking, because that works only on uncompressed files. If a file ("A" in this example) was gzipped, then the gzread would ungzip n (uncompressed) bytes in it in this example, instead of copying it into the memory - but it is not a big deal, in general.

Does anybody know about a similar replacement for writebytes? gzwrite doesn't work for copying (it compresses the array.)

I used the zlibwapi.dll library from http://www.winimage.com/zLibDll/index.html, it is a version of zlib 1.2.5 (written by Jean-Loup Gailly and Mark Adler) built by Gilles Vollant. The code is for a 32-bit system (Windows). That should work in 32-bit Linux after replacing that dll with standard libz.so.1, as well as on 64-bit systems after replacing integer[4] with integer[8] in most places.

In the recent tab, the time goes from 59 min to 2 hours ago. There is no such thing as an hour ago.

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