john gilmore wrote:
For n = 50(10)100 I inverted an identity matrix, a unit upper triangular
matrix, and a unit lower triangular matrix using first HFP and then BFP.
The results, stated as index numbers with BFP=100, are summarized below.
50 60 70 80 90 100 n
101 101 100 103 101 99 I
101 100 103 101 100 100 UUT
103 100 103 102 100 100 ULT
BFP would appear to be very slightly faster, but certainly not in any interesting way.
BFP is significantly more accurate, in the sense that its use yielded less
(indeed almost no) roundoff error for my examples.
Worth noting is that I did not do these calculation is C or C++, neither of which is well adapted to intensive matrix algebra. I did them in Enterprise PL/I 3.8 using double-precision real arithmetic.
Did you mean "in C or C++". Anyway, there's a huge choice of matrix
libraries in C++. Here's an excellent one that totally nukes rolling
your own in PL/1
http://www.boost.org/doc/libs/1_42_0/libs/numeric/ublas/doc/index.htm.
In the event this difference is less important than might be guessed. The current IBM implementations of these three very different languages share the same code generator.
How do you know that? I've looked at the code gen listings for COBOL,
PL/1 and C/C++ and they seem to generate very different code, especially
when optimized.
John Gilmore Ashland, MA 01721-1817 USA
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