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printf: Fix floating-point rounding consistency for RTZ devices (#2202)

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1. In vector test, prepare RTZ answer for RTZ rounding.

2. In mixed_format_random test, for a given float 'arg', the test
previously used 'arg' directly to generate ref_str:
   ```
     ref_str << str_sprintf(format, arg);
   ```

   This approach incorrectly assumes:
   ```
     (float) arg == to_fp(to_str(arg));
   ```

   However, this assumption fails under RTZ rounding. For example: 
   ```
     arg = 0xC642549C 
     to_str(arg) = -12437.152343f 
     to_fp_rtz(-12437.152343f) = 0xC642549B (-0X1.84A936P+13) 
     to_fp_rte(-12437.152343f) = 0xC642549C (-0X1.84A938P+13)
   ```

To address this, the reference result is now computed based on the
literal float string rather than the original 'arg' value.
This commit is contained in:
Chuang-Yu Cheng
2025-02-12 01:46:23 +09:00
committed by GitHub
parent ecd012737f
commit 54afc2e7a5
2 changed files with 38 additions and 2 deletions
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6
test_conformance/printf/test_printf.cpp
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@@ -317,8 +317,10 @@ cl_program makeMixedFormatPrintfProgram(cl_kernel* kernel_ptr,
{
const float max_range = 100000.f;
float arg = get_random_float(-max_range, max_range, gMTdata);
args_str << str_sprintf("%f", arg) << "f, ";
ref_str << str_sprintf(format, arg) << ", ";
std::string arg_str = str_sprintf("%f", arg);
args_str << arg_str << "f, ";
float arg_deviceRound = std::stof(arg_str);
ref_str << str_sprintf(format, arg_deviceRound) << ", ";
}
}
// Restore the original CPU rounding mode