I am experimenting something with the lapack.
I called the 'ssyev'( routine for calculating eigen values of symmetric matrix) , and linked with the lapack.lib, blas.lib, libf2c.lib ( the prebuilt binaries I downloaded).
When I run the program , for 128X128, and 256X256 matrix it takes very less time, less that 1 seconds.
But Other thing I tried is that , I have collected the C files( total no was arround 50) that are the depencencies along with the code for ssyev.
And now the performance is reduced.
for 128X128 matrix it will take 7.9 seconds
and for 256X256 matrix it takes arround 23 seconds.
Why there is so much difference?
It seems to me I might be mising the compiler flags, what are the other issues that c'd be responsible?
Please tell me the compiler flags/optimizations I should set while compiling those 50 C files to get the comparable performance.