[Tarantool-patches] [PATCH v2 1/4] tuple: don't truncate float in :update()
Vladislav Shpilevoy
v.shpilevoy at tarantool.org
Wed Feb 5 01:53:44 MSK 2020
Before the patch there were the rules:
* float +/- double = double
* double +/- double = double
* float +/- float = float
The rules were applied regardless of values. That led to a problem
when float + float exceeding maximal float value could fit into
double, but was stored as an infinity.
The patch makes so that if a floating point arithmetic operation
result fits into float, it is stored as float. Otherwise as
double. Regardless of initial types.
This alongside saves some memory for cases when doubles can be
stored as floats, and therefore takes 4 less bytes. Although
these cases are rare, because any not integer value stored in a
double may have a long garbage tail in its fraction.
Closes #4701
---
src/box/xrow_update_field.c | 10 ++++--
test/box/update.result | 65 +++++++++++++++++++++++++++++++++++++
test/box/update.test.lua | 45 +++++++++++++++++++++++++
3 files changed, 117 insertions(+), 3 deletions(-)
diff --git a/src/box/xrow_update_field.c b/src/box/xrow_update_field.c
index 7c0f5fb5e..6ac29de5d 100644
--- a/src/box/xrow_update_field.c
+++ b/src/box/xrow_update_field.c
@@ -32,6 +32,8 @@
#include "tuple_format.h"
#include "mp_extension_types.h"
+#include <float.h>
+
/* {{{ Error helpers. */
/** Take a string identifier of a field being updated by @a op. */
@@ -400,13 +402,15 @@ xrow_update_arith_make(struct xrow_update_op *op,
unreachable();
break;
}
- if (lowest_type == XUPDATE_TYPE_DOUBLE) {
+ float fc = (float) c;
+ if ((lowest_type == XUPDATE_TYPE_DOUBLE && c != (double) fc) ||
+ (lowest_type == XUPDATE_TYPE_FLOAT &&
+ (c >= FLT_MAX || c <= -FLT_MAX))) {
ret->type = XUPDATE_TYPE_DOUBLE;
ret->dbl = c;
} else {
- assert(lowest_type == XUPDATE_TYPE_FLOAT);
ret->type = XUPDATE_TYPE_FLOAT;
- ret->flt = (float)c;
+ ret->flt = fc;
}
} else {
decimal_t a, b, c;
diff --git a/test/box/update.result b/test/box/update.result
index 28ba47831..dfbd8714f 100644
--- a/test/box/update.result
+++ b/test/box/update.result
@@ -1647,3 +1647,68 @@ t:update({{'=', '[2].d.g', 6000}, {'#', '[2].d.old.old', 1}})
s:drop()
---
...
+--
+-- gh-4701: arith operations should not truncate result when
+-- float + float fits double.
+--
+msgpackffi = require('msgpackffi')
+---
+...
+mp_array_1 = 0x91
+---
+...
+mp_double = 0xcb
+---
+...
+mp_float = 0xca
+---
+...
+flt_max = 3.402823466e+38
+---
+...
+uint_max = 18446744073709551615ULL
+---
+...
+-- Double + double is float if result fits. \
+-- Double + double is double if result does not fit float. \
+-- Double + float is float if result fits. \
+-- Double + float is double if result does not fit float. \
+-- Float + float is float when no overflow. \
+-- Float + float is double when overflow. \
+-- Float + int is float when fits the float range. \
+-- Precision matters too. Double is used when need to avoid \
+-- precision loss. \
+tests = { \
+ {{'double', 1}, {'double', 1}, mp_float}, \
+ {{'double', flt_max}, {'double', flt_max}, mp_double}, \
+ {{'double', 1}, {'float', 1}, mp_float}, \
+ {{'double', flt_max}, {'float', flt_max}, mp_double}, \
+ {{'float', 1}, {'float', 1}, mp_float}, \
+ {{'float', flt_max}, {'float', flt_max}, mp_double}, \
+ {{'float', -flt_max}, {'float', -flt_max}, mp_double}, \
+ {{'float', 1}, {'int', 1}, mp_float}, \
+ {{'float', flt_max}, {'uint64_t', uint_max}, mp_double}, \
+ {{'float', 1.0001}, {'double', 1.0000000000001}, mp_double}, \
+}
+---
+...
+err = nil
+---
+...
+for i, test in pairs(tests) do \
+ local val1 = ffi.cast(test[1][1], test[1][2]) \
+ local val2 = ffi.cast(test[2][1], test[2][2]) \
+ local t = box.tuple.new({val1}) \
+ t = t:update({{'+', 1, val2}}) \
+ local m = msgpackffi.encode(t) \
+ if m:byte(1) ~= mp_array_1 or m:byte(2) ~= test[3] then \
+ err = {i, test, t, m:byte(1), m:byte(2)} \
+ break \
+ end \
+end
+---
+...
+err
+---
+- null
+...
diff --git a/test/box/update.test.lua b/test/box/update.test.lua
index 314ebef05..74f9c62e2 100644
--- a/test/box/update.test.lua
+++ b/test/box/update.test.lua
@@ -597,3 +597,48 @@ t:update({{'=', '[2].d.g', 6000}, {'=', '[2].d.new.new', -1}})
t:update({{'=', '[2].d.g', 6000}, {'#', '[2].d.old.old', 1}})
s:drop()
+
+--
+-- gh-4701: arith operations should not truncate result when
+-- float + float fits double.
+--
+msgpackffi = require('msgpackffi')
+mp_array_1 = 0x91
+mp_double = 0xcb
+mp_float = 0xca
+flt_max = 3.402823466e+38
+uint_max = 18446744073709551615ULL
+tests = { \
+-- Double + double is float if result fits. \
+ {{'double', 1}, {'double', 1}, mp_float}, \
+-- Double + double is double if result does not fit float. \
+ {{'double', flt_max}, {'double', flt_max}, mp_double}, \
+-- Double + float is float if result fits. \
+ {{'double', 1}, {'float', 1}, mp_float}, \
+-- Double + float is double if result does not fit float. \
+ {{'double', flt_max}, {'float', flt_max}, mp_double}, \
+-- Float + float is float when no overflow. \
+ {{'float', 1}, {'float', 1}, mp_float}, \
+-- Float + float is double when overflow. \
+ {{'float', flt_max}, {'float', flt_max}, mp_double}, \
+ {{'float', -flt_max}, {'float', -flt_max}, mp_double}, \
+-- Float + int is float when fits the float range. \
+ {{'float', 1}, {'int', 1}, mp_float}, \
+ {{'float', flt_max}, {'uint64_t', uint_max}, mp_double}, \
+-- Precision matters too. Double is used when need to avoid \
+-- precision loss. \
+ {{'float', 1.0001}, {'double', 1.0000000000001}, mp_double}, \
+}
+err = nil
+for i, test in pairs(tests) do \
+ local val1 = ffi.cast(test[1][1], test[1][2]) \
+ local val2 = ffi.cast(test[2][1], test[2][2]) \
+ local t = box.tuple.new({val1}) \
+ t = t:update({{'+', 1, val2}}) \
+ local m = msgpackffi.encode(t) \
+ if m:byte(1) ~= mp_array_1 or m:byte(2) ~= test[3] then \
+ err = {i, test, t, m:byte(1), m:byte(2)} \
+ break \
+ end \
+end
+err
--
2.21.1 (Apple Git-122.3)
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