From cbce72469eadfb29bc88bcc4c07afe84872c60f5 Mon Sep 17 00:00:00 2001
From: Haoyang Li <haoyangl@nvidia.com>
Date: Wed, 18 Oct 2023 18:22:05 +0800
Subject: [PATCH] Add float to string kernel

Signed-off-by: Haoyang Li <haoyangl@nvidia.com>
---
 src/main/cpp/src/cast_float_to_string.cu      | 23 ++++++++++++-------
 .../nvidia/spark/rapids/jni/CastStrings.java  | 10 ++++++++
 thirdparty/cudf                               |  2 +-
 3 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/src/main/cpp/src/cast_float_to_string.cu b/src/main/cpp/src/cast_float_to_string.cu
index 3560c375e3..13a71754e4 100644
--- a/src/main/cpp/src/cast_float_to_string.cu
+++ b/src/main/cpp/src/cast_float_to_string.cu
@@ -55,13 +55,13 @@ struct ftos_converter {
   static constexpr unsigned int significant_digits = 17;
   // maximum power-of-10 that will fit in 32-bits
   // static constexpr unsigned long long nine_digits = 1000000000;  // 1x10^9
-  static constexpr unsigned long long fifteen_digits = 1000000000000000;
+  // static constexpr unsigned long long fifteen_digits = 1000000000000000;
   static constexpr unsigned long long sixteen_digits = 10000000000000000;
   // Range of numbers here is for normalizing the value.
   // If the value is above or below the following limits, the output is converted to
   // scientific notation in order to show (at most) the number of significant digits.
-  static constexpr double upper_limit = 1000000000;  // max is 1x10^9
-  static constexpr double lower_limit = 0.0001;      // printf uses scientific notation below this
+  static constexpr double upper_limit = 10000000;  // max is 1x10^7
+  static constexpr double lower_limit = 0.001;      // printf uses scientific notation below this
   // Tables for doing normalization: converting to exponent form
   // IEEE double float has maximum exponent of 305 so these should cover everything
   double const upper10[9]  = {10, 100, 10000, 1e8, 1e16, 1e32, 1e64, 1e128, 1e256};
@@ -119,8 +119,16 @@ struct ftos_converter {
       }
     }
     //
-    int decimal_places = significant_digits - (exp10? 2 : 1);
-    unsigned long long max_digits = (exp10? fifteen_digits : sixteen_digits);
+    // int decimal_places = significant_digits - (exp10? 2 : 1);
+    // unsigned long long max_digits = (exp10? fifteen_digits : sixteen_digits);
+    int decimal_places = significant_digits - 1;
+    unsigned long long max_digits = sixteen_digits;
+    double temp_value = value;
+    while (temp_value < 1.0 && temp_value > 0.0) {
+      max_digits *= 10;
+      temp_value *= 10.0;
+      decimal_places++;
+    }
     integer                 = (unsigned int)value;
     for (unsigned int i = integer; i >= 10; i /= 10) {
       --decimal_places;
@@ -194,7 +202,7 @@ struct ftos_converter {
     // decimal
     *ptr++ = '.';
     if (decimal_places) {
-      char buffer[17];
+      char buffer[18];
       char* pb = buffer;
       while (decimal_places--) {
         *pb++ = (char)('0' + (decimal % 10));
@@ -232,7 +240,7 @@ struct ftos_converter {
       value = -value;
       bneg  = true;
     }
-    if (std::isinf(value)) return 3 + (int)bneg;  // Inf
+    if (std::isinf(value)) return 8 + (int)bneg;  // Inf
 
     // dissect float into parts
     unsigned int integer = 0;
@@ -261,7 +269,6 @@ struct ftos_converter {
         count ++;
         exp10 = -exp10;
       }
-      count += (int)(exp10 < 10);  // padding
       while (exp10 > 0) {
         exp10 /= 10;
         ++count;
diff --git a/src/main/java/com/nvidia/spark/rapids/jni/CastStrings.java b/src/main/java/com/nvidia/spark/rapids/jni/CastStrings.java
index 7a31b0241b..3002e1cdab 100644
--- a/src/main/java/com/nvidia/spark/rapids/jni/CastStrings.java
+++ b/src/main/java/com/nvidia/spark/rapids/jni/CastStrings.java
@@ -90,6 +90,16 @@ public static ColumnVector fromFloat(ColumnView cv) {
     return new ColumnVector(fromFloat(cv.getNativeView()));
   }
 
+  /**
+   * Convert a decimal column to a string column.
+   *
+   * @param cv the column data to process
+   * @return the converted column
+   */
+  public static ColumnVector fromDecimal(ColumnView cv) {
+    return new ColumnVector(fromDecimal(cv.getNativeView()));
+  }
+
   /**
    * Convert a string column to a given floating-point type column.
    *
diff --git a/thirdparty/cudf b/thirdparty/cudf
index 5f05c180b8..fa4e8ab1af 160000
--- a/thirdparty/cudf
+++ b/thirdparty/cudf
@@ -1 +1 @@
-Subproject commit 5f05c180b80b70fc09ea58aef2494c57edc44b9c
+Subproject commit fa4e8ab1af4acfd2c88a619b4d9693f4a5fda168