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| author | Hans Boehm <hboehm@google.com> | 2018-01-10 23:08:39 +0000 |
|---|---|---|
| committer | android-build-merger <android-build-merger@google.com> | 2018-01-10 23:08:39 +0000 |
| commit | 773a95a42323114e0363a7653cc3d37b5b9d0fef (patch) | |
| tree | fc0d0fd7c34a014d690a7bee8b4b315ebfbab770 | |
| parent | a8af147c43a3c4454ff83583f5bfdcf7b5a84323 (diff) | |
| parent | dd41fd08d7d6203c17eefcc5ae25042f0cd90989 (diff) | |
| download | crcalc-773a95a42323114e0363a7653cc3d37b5b9d0fef.tar.gz | |
Fix a couple of square root related performance problems am: 568c8e610b am: 8d8c9f82a4
am: dd41fd08d7
Change-Id: Ie5fade5ea1555362d2db51eb281a89fdccd911af
| -rw-r--r-- | src/com/hp/creals/CR.java | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/src/com/hp/creals/CR.java b/src/com/hp/creals/CR.java index d051050..9e10b51 100644 --- a/src/com/hp/creals/CR.java +++ b/src/com/hp/creals/CR.java @@ -1494,15 +1494,16 @@ class sqrt_CR extends CR { op = x; min_prec = min_p; max_appr = max_a; + appr_valid = true; } final int fp_prec = 50; // Conservative estimate of number of // significant bits in double precision // computation. final int fp_op_prec = 60; protected BigInteger approximate(int p) { - int max_prec_needed = 2*p - 1; - int msd = op.msd(max_prec_needed); - if (msd <= max_prec_needed) return big0; + int max_op_prec_needed = 2*p - 1; + int msd = op.msd(max_op_prec_needed); + if (msd <= max_op_prec_needed) return big0; int result_msd = msd/2; // +- 1 int result_digits = result_msd - p; // +- 2 if (result_digits > fp_prec) { @@ -1510,11 +1511,12 @@ class sqrt_CR extends CR { int appr_digits = result_digits/2 + 6; // This should be conservative. Is fewer enough? int appr_prec = result_msd - appr_digits; - BigInteger last_appr = get_appr(appr_prec); int prod_prec = 2*appr_prec; + // First compute the argument to maximal precision, so we don't end up + // reevaluating it incrementally. BigInteger op_appr = op.get_appr(prod_prec); - // Slightly fewer might be enough; - // Compute (last_appr * last_appr + op_appr)/(last_appr/2) + BigInteger last_appr = get_appr(appr_prec); + // Compute (last_appr * last_appr + op_appr) / last_appr / 2 // while adjusting the scaling to make everything work BigInteger prod_prec_scaled_numerator = last_appr.multiply(last_appr).add(op_appr); |