From 019a902fed05d173edcf3f0ae116f774334a25dc Mon Sep 17 00:00:00 2001
From: Tomasz Sowa <t.sowa@ttmath.org>
Date: Sun, 14 Jun 2009 19:55:15 +0000
Subject: [PATCH] changed: small optimization in Big::ExpSurrounding0() and
 Big::LnSurrounding1()          the remainder from a division '%' was changed
 with a bitwise And operation '&'          ((i % 5) == 0) was changed to: ((i
 & 3) == 0) - it means ((i % 4) == 0)          now the test if performed after
 4 iterations (early were after 5 iterations)          we can do that when the
 divisor is a power of 2 changed: optimization in Factorial()          we're
 testing WasStopSignal() only after a few iterations          it's faster now
 about 4 times on GCC 4.3.3 (when stop object is provided to the factorial)

git-svn-id: svn://ttmath.org/publicrep/ttmath/trunk@161 e52654a7-88a9-db11-a3e9-0013d4bc506e
---
 ttmath/ttmath.h    | 28 ++++++++++++++++++----------
 ttmath/ttmathbig.h | 13 ++++---------
 2 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/ttmath/ttmath.h b/ttmath/ttmath.h
index b807564..3883108 100644
--- a/ttmath/ttmath.h
+++ b/ttmath/ttmath.h
@@ -1902,13 +1902,16 @@ namespace ttmath
 
 		while( !carry && multipler<maxvalue  )
 		{
-			// !! the test here we don't have to make in all iterations (performance)
-			if( stop && stop->WasStopSignal() )
+			if( stop && (multipler & 127)==0 ) // it means 'stop && (multipler % 128)==0'
 			{
-				if( err )
-					*err = err_interrupt;
+				// after each 128 iterations we make a test
+				if( stop->WasStopSignal() )
+				{
+					if( err )
+						*err = err_interrupt;
 
-			return 2;
+					return 2;
+				}
 			}
 			
 			++multipler;
@@ -1932,20 +1935,25 @@ namespace ttmath
 
 		one.SetOne();
 		uint carry = 0;
+		uint iter = 1; // only for testing the stop object
 
 		while( !carry && multipler < x )
 		{
-			// !! the test here we don't have to make in all iterations (performance)
-			if( stop && stop->WasStopSignal() )
+			if( stop && (iter & 31)==0 ) // it means 'stop && (iter % 32)==0'
 			{
-				if( err )
-					*err = err_interrupt;
+				// after each 32 iterations we make a test
+				if( stop->WasStopSignal() )
+				{
+					if( err )
+						*err = err_interrupt;
 
-			return 2;
+					return 2;
+				}
 			}
 			
 			carry += multipler.Add(one);
 			carry += result.Mul(multipler);
+			++iter;
 		}
 
 		if( err )
diff --git a/ttmath/ttmathbig.h b/ttmath/ttmathbig.h
index 422d563..2b5057a 100644
--- a/ttmath/ttmathbig.h
+++ b/ttmath/ttmathbig.h
@@ -1399,19 +1399,17 @@ public:
 		denominator.SetOne();
 		denominator_i.SetOne();
 
-		// every 'step_test' times we make a test
-		const uint step_test = 5;
 		uint i;
 		old_value = *this;
 
-		// we begin from 1 in order to not testing at the beginning
+		// we begin from 1 in order to not test at the beginning
 	#ifdef TTMATH_CONSTANTSGENERATOR
 		for(i=1 ; true ; ++i)
 	#else
 		for(i=1 ; i<=TTMATH_ARITHMETIC_MAX_LOOP ; ++i)
 	#endif
 		{
-			bool testing = ((i % step_test) == 0);
+			bool testing = ((i & 3) == 0); // it means '(i % 4) == 0'
 
 			next_part = numerator;
 
@@ -1567,20 +1565,17 @@ public:
 		SetZero();
 
 		old_value = *this;
-		
-		// every 'step_test' times we make a test
-		const uint step_test = 5;
 		uint i;
 
 
 	#ifdef TTMATH_CONSTANTSGENERATOR
 		for(i=1 ; true ; ++i)
 	#else
-		// we begin from 1 in order to not testing at the beginning
+		// we begin from 1 in order to not test at the beginning
 		for(i=1 ; i<=TTMATH_ARITHMETIC_MAX_LOOP ; ++i)
 	#endif
 		{
-			bool testing = ((i % step_test) == 0);
+			bool testing = ((i & 3) == 0); // it means '(i % 4) == 0'
 
 			next_part = x1;