Changeset 39058 for trunk

Timestamp:

Nov 6, 2015, 10:24:47 AM (11 years ago)

Author:

eugene

Message:

try frexp instead of log & pow in sprintf_float,double (not an improvement)

Location:

trunk/Ohana/src/libohana

Files:

• Makefile (modified) (2 diffs)
• doc/sprintf_floats.txt (added)
• src/sprintf_floats.c (moved) (moved from trunk/Ohana/src/libohana/src/print_floats.c ) (7 diffs)
• test/sprintf_floats.c (moved) (moved from trunk/Ohana/src/libohana/test/print_floats.c ) (3 diffs)

trunk/Ohana/src/libohana/Makefile

@@ -51 +51 @@
 $(SRC)/errors.$(ARCH).o  \
 $(SRC)/gprint.$(ARCH).o  \
-$(SRC)/print_floats.$(ARCH).o    \
+$(SRC)/sprintf_floats.$(ARCH).o  \
 $(SRC)/version.$(ARCH).o
 
@@ -65 +65 @@
 $(DESTLIB)/libohana.$(DLLTYPE): $(LIB)/libohana.$(ARCH).$(DLLTYPE)
 
-TESTPROG = print_floats
+TESTPROG = sprintf_floats
 # TESTPROG = memtest typetest string 
 

trunk/Ohana/src/libohana/src/sprintf_floats.c

@@ -1 +1 @@
 # include <ohana.h>
 
+# define USE_LOGS 1
 # define NSIGFIG_FLT  7
 # define NEXPFIG_FLT  2
+# define M_LOG2_10 (M_LN10 / M_LN2)
+# define M_LOG10_2 (M_LN2 / M_LN10)
 
 // returns the number of bytes written EXCLUDING the ending NULL char
@@ -22 +25 @@
   double pvalue = fabs(value);
 
-  int isPositiveExp = (pvalue >= 1.0);
-
+# if (USE_LOGS)
   // get the exponent
   double Exponent = log10(pvalue);
@@ -34 +36 @@
 
   double Mantissa = pvalue / power;
+
+# else
+
+  // p = frexpf (x,n) returns (p,n) where x = p*2^n
+  // we want f = q*10^m
+  // s = n * log10(2)
+  // m = floor(s)
+  // r = s - m
+  // t = r * log2(10)
+  // q = p * 2^t
+  
+  int n;
+  double p = frexp (pvalue, &n);
+  double s = n * M_LOG10_2;
+  int m = floor(s);
+  double r = s - m;
+  double t = r * M_LOG2_10;
+  double q = p * pow(2.0, t);
+
+  if (q < 1.0) {
+    q *= 10.0;
+    m --;
+  }
+
+  int iExponent = m;
+  double Mantissa = q;
+# endif
 
   // multiplier here must be 10^(NSIGFIG_FLT + 1)
@@ -53 +82 @@
   iMantissa = iMantissa / 10;
   if (roundUp) iMantissa ++;
+  if (iMantissa > 99999999) {
+    iMantissa = iMantissa / 10;
+    iExponent ++;
+  }
+  int isPositiveExp = (iExponent >= 0);
 
   // now write out the Mantissa backwards as an integer, but include a decimal point
@@ -100 +134 @@
   double pvalue = fabs(value);
 
-  int isPositiveExp = (pvalue >= 1.0);
-
+# if (USE_LOGS)
   // get the exponent
   double Exponent = log10(pvalue);
@@ -112 +145 @@
 
   double Mantissa = pvalue / power;
+
+# else
+
+  // p = frexpf (x,n) returns (p,n) where x = p*2^n
+  // we want f = q*10^m
+  // s = n * log10(2)
+  // m = floor(s)
+  // r = s - m
+  // t = r * log2(10)
+  // q = p * 2^t
+  
+  int n;
+  double p = frexp (pvalue, &n);
+  double s = n * M_LOG10_2;
+  int m = floor(s);
+  double r = s - m;
+  double t = r * M_LOG2_10;
+  double q = p * pow(2.0, t);
+
+  if (q < 1.0) {
+    q *= 10.0;
+    m --;
+  }
+
+  int iExponent = m;
+  double Mantissa = q;
+# endif
 
   // multiplier here must be 10^(NSIGFIG_DBL + 1)
@@ -131 +191 @@
   iMantissa = iMantissa / 10;
   if (roundUp) iMantissa ++;
+
+  // 1000000000000000
+  //  999999999999999
+
+  if (iMantissa > 999999999999999) {
+    iMantissa = iMantissa / 10;
+    iExponent ++;
+  }
+
+  int isPositiveExp = (iExponent >= 0);
 
   // now write out the Mantissa backwards as an integer, but include a decimal point

trunk/Ohana/src/libohana/test/sprintf_floats.c

@@ -2 +2 @@
 # include "tap_ohana.h"
 
+# define DO_FLOATS 1
+# define DO_DOUBLES 1
 # define NTESTS 300000
 
@@ -34 +36 @@
 int main (void) {
 
-  plan_tests (20);
+  // plan_tests (2013);
+  plan_tests (4026);
 
   diag ("libohana print_float.c tests");
 
   /*** sprint_float ***/
-  if (1) {
+  if (DO_FLOATS) {
     int Noutput;
     char output[128];
@@ -81 +84 @@
   
   /*** sprint_double ***/
-  if (1) {
+  if (DO_DOUBLES) {
     int Noutput;
     char output[128];