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ppm-guest pushed a commit to annotated tag v0.35
in repository libmath-prime-util-perl.
commit 1ff0a217e8d3745b443ee6c203fec6e5ae1a1050
Author: Dana Jacobsen <d...@acm.org>
Date: Fri Dec 6 17:12:36 2013 -0800
Restructure step 7 phi summation to streamline inner loop
---
lmo.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/lmo.c b/lmo.c
index cd54252..167db82 100644
--- a/lmo.c
+++ b/lmo.c
@@ -571,18 +571,19 @@ UV _XS_LMO_pi(UV n)
if (start < ss.prime_index[k])
ss.prime_index[k] = start;
}
- /* Step 7: For KM <= K < Pi_M: For primes[k+2] <= x <= M,
- * sum phi(n / (x*primes[k+1]), k). */
+ /* Step 7: For KM <= K < Pi_M: For primes[k+2] <= x <= M, sum
+ * phi(n / (x*primes[k+1]), k). The inner for loop can be parallelized. */
for (; k < step7_max; k++) {
remove_primes(k, k, &ss, primes);
if (ss.prime_index[k] >= k+2) {
UV pk = primes[k+1];
- for (j = ss.prime_index[k]; j >= k+2; j--) {
- UV divisor = pk * primes[j];
- if (divisor <= least_divisor) break;
- sum1 += sieve_phi(n / divisor);
- }
- ss.prime_index[k] = j;
+ UV endj = ss.prime_index[k];
+ while (endj > 7 && endj-7 >= k+2 && pk*primes[endj-7] > least_divisor)
endj -= 8;
+ while ( endj >= k+2 && pk*primes[endj ] > least_divisor)
endj--;
+ /* Now that we know how far to go, do the summations */
+ for (j = ss.prime_index[k]; j > endj; j--)
+ sum1 += sieve_phi(n / (pk*primes[j]));
+ ss.prime_index[k] = endj;
}
}
/* Restrict work for the above loop when we know it will be empty. */
--
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