<div dir="ltr"><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt" id="docs-internal-guid-28ab298a-6cc6-4af6-c733-3e8149cb9dd3"><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Currently OpenCL support is hidden behind an environment variable called ‘CYCLES_OPENCL_TEST’. I believe this should change for 2.69 for the following reasons.</span></p>
<br><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"></span><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">1) It discourages use of the OpenCL backend. While it is true the experience of using opencl might be less good than using cuda on some platforms and fail totally on some others (AMD/ATI GPU’s) it is not Blender fault as much as it is the vendors providing not the best possible OpenCL support. Users actually complaining to them would help us.</span></p>
<br><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"></span><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">2) It discourages development. If no one uses it no one cares and no one will invest time to keep OpenCL working or make it work more great. </span></p>
<br><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"></span><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">3) It discourages industry backing the project. They could perceive the current state of our OpenCL support as not enabled or even non existent.</span></p>
<br><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"></span><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">All of this enforces the chicken - egg problem we are having with regards to OpenCL</span></p>
<br><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"></span><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">I would like to propose that we change this and enable OpenCL before releasing 2.69. Given how close we are to the blender 2.7x development changes and the special status that will give 2.69x the change should really happen this cycles to have any impact.</span></p>
<br><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"></span><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Maybe we could add a warning in some cases for platforms where we know using it is not recommended.  </span></p>
<br><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"></span><p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">Further I think we should communicate very clearly with the vendors of GPU and GPU like platforms that we might need something like Nvidia’s maxrregcount setting as we do not want cycles complexity to eat up all to available registers and thereby decrease the amount of threads to much. For performance on those platforms we need a lot of threads even though that implies spilling and for the best performance we will most likely need to be able to influence how much threads we want to use.</span></p>
<br><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline"></span><span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:normal;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline">As a last point I would like to express how stunning it is to me that specifically AMD seems to have such a hard time getting these features in place. I think they need them to compete in the GPU space and they need to compete their to make the their APU strategy work. </span></div>