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-rw-r--r--src/math/sqrt_data.h13
1 files changed, 13 insertions, 0 deletions
diff --git a/src/math/sqrt_data.h b/src/math/sqrt_data.h
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+#ifndef _SQRT_DATA_H
+#define _SQRT_DATA_H
+
+#include <features.h>
+#include <stdint.h>
+
+/* if x in [1,2): i = (int)(64*x);
+ if x in [2,4): i = (int)(32*x-64);
+ __rsqrt_tab[i]*2^-16 is estimating 1/sqrt(x) with small relative error:
+ |__rsqrt_tab[i]*0x1p-16*sqrt(x) - 1| < -0x1.fdp-9 < 2^-8 */
+extern hidden const uint16_t __rsqrt_tab[128];
+
+#endif