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Math Forum / Math Software / Maple / June 2009C(++) source to write an m-file
Hi, I have a (big) matrix computed by a C++ program. I'd like to write the data from within that program to a (binary) file (a Maple m-file) which can be read by Maple for further processing like plotting. Does anybody know some C(++) source which does this? Many thanks for a hint, Helmut.  SignatureHelmut Jarausch Lehrstuhl fuer Numerische Mathematik RWTH - Aachen University D 52056 Aachen, Germany > Hi, > > I have a (big) matrix computed by a C++ program. > I'd like to write the data from within that program to a (binary) file (a > Maple m-file) > which can be read by Maple for further processing like plotting. It's simplest to use text files rather than binary files. I don't think the .m format offers any particular advantages, and it has the disadvantage that compatibility between different releases of Maple is not guaranteed. SignatureRobert Israel israel@math.MyUniversitysInitials.ca Department of Mathematics http://www.math.ubc.ca/~israel University of British Columbia Vancouver, BC, Canada >> Hi, >> [quoted text clipped - 6 lines] > the .m format offers any particular advantages, and it has the disadvantage > that compatibility between different releases of Maple is not guaranteed. Thanks, but since the matrix has a quarter of a million items I thought a binary format would be smaller and faster to read/write. Helmut. SignatureHelmut Jarausch Lehrstuhl fuer Numerische Mathematik RWTH - Aachen University D 52056 Aachen, Germany >>> Hi, >>> [quoted text clipped - 14 lines] > > Helmut. Uncompressed that would be ~ 7 MB which is not so big for an usual PC and I would guess most time is spent by Maple to validate and filling by reading such a file. >>>> Hi, >>>> [quoted text clipped - 19 lines] > an usual PC and I would guess most time is spent by Maple > to validate and filling by reading such a file. Even worse, read-ing the file was nearly a no-op on my machine. But plotting (even a much smaller 31x31 Matrix (instead of 511x511)) with plots[surfdata] takes a lot of time (on my PhenomII 3GHz) And still worser the export to GIF or JPEG seems to be completely broken since the right most 1/3 of the image is moved to the left. This is with Maple13 (on AMD64) Have others made similar bad experience? Helmut. SignatureHelmut Jarausch Lehrstuhl fuer Numerische Mathematik RWTH - Aachen University D 52056 Aachen, Germany >>>>> Hi, >>>>> [quoted text clipped - 31 lines] > > Helmut. I forgot, whether there is a really efficient way (IIRC it is something like 'WriteMatrix' or so ...): Digits:=18; # to have full length for floats fName:="D:\\temp\\tst.txt"; A:=Array(1 .. 511^2, 'i -> evalhf(1/i)', datatype=float[8]); fd := fopen(fName,WRITE,TEXT); st:=time(): writedata(fd,convert(A,listlist)); time() - st; fclose(fd); needs about 8.5 sec and reading needs twice the time: fd := fopen(fName,READ,TEXT); st:=time(): inData:=readdata(fd, 1): time() - st; 17.906 Converting to Array (Upper Case) is ~ 0.5 sec st:=time(): B:=convert(inData, Array, datatype=float[8]); time() - st; You also may turn off autosave (as the Maple file is large) and may wish to delete the Arrays (mark with mouse and delete), otherwise they are stored if the file is saved. Using Maple13 classic on a medium sized PC with WIN XP. > >>>>> Hi, > >>>>> [quoted text clipped - 34 lines] > I forgot, whether there is a really efficient way (IIRC it is > something like 'WriteMatrix' or so ...): Perhaps you're thinking of writebytes and readbytes. fName:="D:\\temp\\tst.txt"; A:=Array(1 .. 511^2, 'i -> evalhf(1/i)', datatype=float[8]); st:= time(): writebytes(fName, A); time()-st; fclose(fName); This took 0.249 seconds on my computer in Maple 13 Classic under Windows Vista, where your writedata example took 4.509 sec. The resulting file is 2041 KB, compared to 4333 KB for the writedata version. st:= time(): B:= Array(1..511^2,datatype=float[8]); readbytes(fName,B); time()-st; Takes 0.234 seconds. > Digits:=18; # to have full length for floats > [quoted text clipped - 27 lines] > Using Maple13 classic on a medium sized PC with WIN XP. > SignatureRobert Israel israel@math.MyUniversitysInitials.ca Department of Mathematics http://www.math.ubc.ca/~israel University of British Columbia Vancouver, BC, Canada >>>>>>> Hi, >>>>>>> [quoted text clipped - 50 lines] > > Takes 0.234 seconds. Thanks - that's convincing :-) >> Digits:=18; # to have full length for floats >> [quoted text clipped - 26 lines] >> >> Using Maple13 classic on a medium sized PC with WIN XP. |
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