Hello All:
There is a typo error.
The fig(2) is corrected as follows.
For ( I = 1; I < size ; i+=3)
{
X[i] = z[i] * ( y[i] - x[i-1]);
X[i+1] = z[i] * ( y[i] - x[i]);
X[i+2] = z[i] * ( y[i] - x[i+1]]); }
Fig(2).
Thanks & Regards
Ajit
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Ajit
Kumar Agarwal
Sent: Saturday, March 07, 2015 3:31 PM
To: Richard Biener; [email protected]
Cc: Vinod Kathail; Shail Aditya Gupta; Vidhumouli Hunsigida; Nagaraju Mekala
Subject: Proposal on Unrolling factor based on Data reuse.
Hello All:
I would like to propose the Unrolling factor based on Data reuse between
different iterations. This combines the data reuse of different iterations
into single iterations. There is a use of MaxFactor which decides on the
calculation of unroll factor based on Data reuse.The MaxFactor is calculated
based on (MaxInsts/LoopBodyInsts). The MaxInsts decides on the number of
instruction that doesn't degrades on the instruction cache. The calculation of
the MaxInsts also considers the def and use distance for the max insts that
does not degrades the instruction cache which leads to increase in the Live
range width and multiplied with the MaxInsts calculated based on Instruction
cache.
The following example from Livermore Loops benchmarks.
The data reuse from the previous iteration to current iteration makes the data
reuse. Unrolling the Loop in Fig(1) can Reuse the data and thus increasing the
performance. The unrolled loop is unrolled 3 times given in Fig(2) based on the
algorithm for Calculation of unrolling factor used as given in Fig(3).
For ( I = 1; I < size; i++ )
{
X[i] = z[i] * ( y[i] - x[i-1]);
}
Fig(1).
For ( I = 1; I < size ; i+=3)
{
X[i] = z[i] * ( y[i] - x[i-1]);
X[i+1] = z[i] * ( y[i] - x[i]);
X[i] = z[i] * ( y[i] - x[i+1]]); }
Fig(2).
Algorithm for unroll factor based on data reuse.
If ( data_reuse == true)
{
Unroll_factor = Reuse_distance +1;
If(Unroll_factor < MaxFactor)
Return unroll_factor;;
Else{
Unroll_factor = MaxFactor - unroll_factor.
If( unroll_factor < MaxDistance)
Return unroll_factor;
}
}
Fig ( 3).
In the example given above in Fig(1) the data reuse distance and the MaxFactor
calculated based on the maximum number of insts that don't degrades the
instructions caches and doesn't exceed the maximum limit on def and use
distance that increases the width of Live range. The above is considered and
the Loop is 3 times.
Thoughts Please ?
Thanks & Regards
Ajit
