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  1. PO
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    <p>It seems that you have a lot of opportunities to optimize your code. Your x loop executes 128 times, your y loop executes 128*128=16,384 times, and your z loop executes 128^3=2,097,152 times. There are a number of terms inside your z loop that are only dependent on the x, or the y iterations, but they are recalculated at every z iteration. For example, </p> <pre><code>int poxox = plusOffsetX - offsetX; </code></pre> <p>and </p> <pre><code>double poxxpoxox = ((plusOffsetX - x) / (double)poxox); </code></pre> <p>These two terms are being calculated more than 2 million times, but only need to be calculated 128 times if my cursory scan of your function is correct. Move terms to the loop level that is appropriate so you don't waste cycles recalculating the same values many multiple times.</p> <p>Here is your code with basic optimizations made. I'm curious to know how this affects your run times. Several of the terms are only dependent on the iteration value, and are the same for x, y, and z. So I pulled them out entirely and precompute them once. I also have moved the outer mod operations out of the inner loop, and modified the logic to ensure short circuit of the evaluation, which should should remove the majority of mod operations that were previously being executed.</p> <pre><code>int[] offsets = new int[128]; int[] plusOffsets = new int[128]; double[] poii = new double[128]; double[] ioip = new double[128]; for (int i = 0; i &lt; 128; i++) { offsets[i] = (i / SAMPLE_RATE_3D_HOR) * SAMPLE_RATE_3D_HOR; plusOffsets[i] = SAMPLE_RATE_3D_HOR + offsets[i]; double poioi = (double) (plusOffsets[i] - offsets[i]); poii[i] = ((plusOffsets[i] - i) / poioi); ioip[i] = ((i - offsets[i]) / poioi); } float[, ,] DensityMap = new float[128, 128, 128]; float[, ,] PressureMap = new float[128, 128, 128]; for (int x = 0; x &lt; g_CraftWorldConstants.RegionSizeX; x++) { int offsetX = offsets[x]; int plusOffsetX = plusOffsets[x]; double poxxpoxox = poii[x]; double xoxpoxox = ioip[x]; bool xModNot0 = !(x % SAMPLE_RATE_3D_HOR == 0); for (int y = 0; y &lt; g_CraftWorldConstants.RegionSizeY; y++) { int offsetY = offsets[y]; int plusOffsetY = plusOffsets[y]; double poyypoyoy = poii[y]; double yoypoyoy = ioip[y]; bool yModNot0 = !(y % SAMPLE_RATE_3D_VERT == 0); for (int z = 0; z &lt; g_CraftWorldConstants.RegionSizeZ; z++) { //if (!(x % SAMPLE_RATE_3D_HOR == 0 &amp;&amp; y % SAMPLE_RATE_3D_VERT == 0 &amp;&amp; z % SAMPLE_RATE_3D_HOR == 0)) if (xModNot0 || yModNot0 || !(z % SAMPLE_RATE_3D_HOR == 0)) { int offsetZ = offsets[z]; int plusOffsetZ = plusOffsets[z]; double pozzpozoz = poii[z]; double zozpozoz = ioip[z]; double x00 = poxxpoxox * DensityMap[offsetX, offsetY, offsetZ] + xoxpoxox * DensityMap[plusOffsetX, offsetY, offsetZ]; double x10 = poxxpoxox * DensityMap[offsetX, offsetY, plusOffsetZ] + xoxpoxox * DensityMap[plusOffsetX, offsetY, plusOffsetZ]; double x01 = poxxpoxox * DensityMap[offsetX, plusOffsetY, offsetZ] + xoxpoxox * DensityMap[plusOffsetX, plusOffsetY, offsetZ]; double x11 = poxxpoxox * DensityMap[offsetX, plusOffsetY, plusOffsetZ] + xoxpoxox * DensityMap[plusOffsetX, plusOffsetY, plusOffsetZ]; double r0 = poyypoyoy * x00 + yoypoyoy * x01; double r1 = poyypoyoy * x10 + yoypoyoy * x11; DensityMap[x, y, z] = (float)(pozzpozoz * r0 + zozpozoz * r1); double x02 = poxxpoxox * PressureMap[offsetX, offsetY, offsetZ] + xoxpoxox * PressureMap[plusOffsetX, offsetY, offsetZ]; double x12 = poxxpoxox * PressureMap[offsetX, offsetY, plusOffsetZ] + xoxpoxox * PressureMap[plusOffsetX, offsetY, plusOffsetZ]; double x03 = poxxpoxox * PressureMap[offsetX, plusOffsetY, offsetZ] + xoxpoxox * PressureMap[plusOffsetX, plusOffsetY, offsetZ]; double x13 = poxxpoxox * PressureMap[offsetX, plusOffsetY, plusOffsetZ] + xoxpoxox * PressureMap[plusOffsetX, plusOffsetY, plusOffsetZ]; double r2 = poyypoyoy * x02 + yoypoyoy * x03; double r3 = poyypoyoy * x12 + yoypoyoy * x13; PressureMap[x, y, z] = (float)(pozzpozoz * r2 + zozpozoz * r3); } } } } </code></pre>
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    1. POHow to speed up C# math code
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    1. COIt actually made things about 19% faster! this is a huge improvement :) I had previously moved many of those variables up and out of functions on the inside there but I missed all the ones you found, shows just how good another pair of eyes can be. SAMPLE_RATE_3D_HOR is an int too (someone asked), also all the stupid names for variables (like poxxpoxox) are because of resharpers inline function which I used to lazyly remove the 8 inner functions. Thanks this is really helpful, can you see any other things I could do to improve it?
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    2. CO@DanielArmstrong - I've edited my answer to include another optimization that I noticed right after I posted the previous version, but couldn't post until now because I had to drive somewhere. This should improve the speed further. You will need to test to ensure my changes don't bugger up the results.
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    3. CO@DanielArmstrong - I've edited the answer to include one more little optimization to remove around 4 million mod (%) operations, which I think are kind of expensive if the right hand side is not a power of 2.
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