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Replaced use of rcp() and rsqrt() functions with non-approximating re… #20

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Replaced use of rcp() and rsqrt() functions with non-approximating re… #20

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10 changes: 5 additions & 5 deletions ISPC Texture Compressor/ispc_texcomp/kernel.ispc
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Original file line number Diff line number Diff line change
Expand Up @@ -195,7 +195,7 @@ inline void compute_axis3(float axis[3], float covar[6], uniform const int power
for (uniform int p=0; p<3; p++)
norm_sq += axis[p]*axis[p];

float rnorm = rsqrt(norm_sq);
float rnorm = 1.0f / sqrt(norm_sq); // Note: Replaced the original rsqrt() function as it produces subtly different results on different architectures causing non-deterministic output (Intel vs. AMD Ryzen was observed to differ)
for (uniform int p=0; p<3; p++) vec[p] *= rnorm;
}
}
Expand All @@ -219,7 +219,7 @@ inline void compute_axis(float axis[4], float covar[10], uniform const int power
for (uniform int p=0; p<channels; p++)
norm_sq += axis[p]*axis[p];

float rnorm = rsqrt(norm_sq);
float rnorm = 1.0f / sqrt(norm_sq); // Note: Replaced the original rsqrt() function as it produces subtly different results on different architectures causing non-deterministic output (Intel vs. AMD Ryzen was observed to differ)
for (uniform int p=0; p<channels; p++) vec[p] *= rnorm;
}
}
Expand Down Expand Up @@ -296,7 +296,7 @@ inline void pick_endpoints(float c0[3], float c1[3], float block[48], float axis
for (uniform int p=0; p<3; p++)
norm_sq += axis[p]*axis[p];

float rnorm_sq = rcp(norm_sq);
float rnorm_sq = 1.0f / norm_sq; // Note: Replaced the original rcp() function as it produces subtly different results on different architectures causing non-deterministic output (Intel vs. AMD Ryzen was observed to differ)
for (uniform int p=0; p<3; p++)
{
c0[p] = clamp(dc[p]+min_dot*rnorm_sq*axis[p], 0, 255);
Expand All @@ -317,7 +317,7 @@ inline uint32 fast_quant(float block[48], int p0, int p1)
float sq_norm = 0;
for (uniform int p=0; p<3; p++) sq_norm += sq(dir[p]);

float rsq_norm = rcp(sq_norm);
float rsq_norm = 1.0f / sq_norm; // Note: Replaced the original rcp() function as it produces subtly different results on different architectures causing non-deterministic output (Intel vs. AMD Ryzen was observed to differ)

for (uniform int p=0; p<3; p++) dir[p] *= rsq_norm*3;

Expand Down Expand Up @@ -462,7 +462,7 @@ inline void bc1_refine(int pe[2], float block[48], unsigned int32 bits, float dc
float Cxx = 16*sq(3)-2*3*sum_q+sum_qq;
float Cyy = sum_qq;
float Cxy = 3*sum_q-sum_qq;
float scale = 3f * rcp(Cxx*Cyy - Cxy*Cxy);
float scale = 3f * (1.0f / (Cxx*Cyy - Cxy * Cxy)); // Note: Replaced the original rcp() function as it produces subtly different results on different architectures causing non-deterministic output (Intel vs. AMD Ryzen was observed to differ)

for (uniform int p=0; p<3; p++)
{
Expand Down
2 changes: 1 addition & 1 deletion ISPC Texture Compressor/ispc_texcomp/kernel_astc.ispc
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Original file line number Diff line number Diff line change
Expand Up @@ -295,7 +295,7 @@ inline void compute_axis(float axis[4], float covar[10], uniform const int power
for (uniform int p = 0; p < channels; p++)
norm_sq += axis[p] * axis[p];

float rnorm = rsqrt(norm_sq);
float rnorm = 1.0f / sqrt(norm_sq); // Note: Replaced the original rsqrt() function as it produces subtly different results on different architectures causing non-deterministic output (Intel vs. AMD Ryzen was observed to differ)
for (uniform int p = 0; p < channels; p++) vec[p] *= rnorm;
}
}
Expand Down